PATENT DOCUMENT

Publication Number: US-9916080-B2
Application Number: US-201615136782-A
Country: US
Kind Code: B2

Title: Devices and methods for navigating between user interfaces

Abstract:
A method includes: displaying a first view of a first application; detecting a first portion of a first input; if the first portion of the first input meets application-switching criteria, concurrently displaying portions of the first application view and a second application view; while concurrently displaying the portions of the application views, detecting a second portion of the first input; if the second portion of the first input meets first-view display criteria (liftoff of contact detected in a first region), ceasing to display the portion of the second application view and displaying the first application view; and if the second portion of the first input meets multi-view display criteria (liftoff of contact detected in a second region), maintaining concurrent display of a portion of the first application view and a portion of the second application view on the display after detecting the liftoff of the contact.

Claims:
What is claimed is: 
     
       1. A method, comprising:
 at an electronic device with a touch-sensitive display, and one or more sensors that are configured to detect intensities of contacts with the touch-sensitive display: 
 displaying, on the touch-sensitive display, a user interface of an application; 
 while displaying the user interface of the application on the touch-sensitive display, detecting an input that includes detecting a contact at a first location on the touch-sensitive display, wherein the first location corresponds to a first operation within the application, wherein the contact remains stationary at the first location prior to lift-off of the first contact, and wherein the touch-sensitive display includes an open-application-selection region; and, 
 in response to detecting the input on the touch-sensitive display:
 in accordance with a determination that the input occurred inside of the open-application-selection region and that the input meets intensity criteria, including a criterion that is met when the input includes an increase in intensity of the contact above a first intensity threshold, performing a system function that is independent of the application without performing the first operation within the application, wherein performing the system function includes displaying an open-application-selection user interface that includes representations of a plurality of open applications, including one or more representations of open applications that were not displayed prior to detecting the input on the touch-sensitive display; and 
 in accordance with a determination that the input occurred inside of the open-application-selection region and that the input does not meet the intensity criteria, performing the first operation within the application based on the input without performing the system function, wherein performing the first operation includes changing the user interface of the application without displaying the open-application-selection user interface. 
 
 
     
     
       2. The method of  claim 1 , including:
 in accordance with a determination that the input occurred outside of the open-application-selection region, performing an operation within the application based on the input. 
 
     
     
       3. The method of  claim 1 , wherein the open-application-selection user interface includes snapshots of open applications displayed in an overlapping 3D arrangement. 
     
     
       4. The method of  claim 1 , wherein the open-application-selection user interface includes snapshots of open applications. 
     
     
       5. The method of  claim 1 , wherein the open-application-selection region is on a portion of the display that, prior to detecting the input, includes the user interface of the application. 
     
     
       6. The method of  claim 1 , including:
 while displaying the open-application-selection user interface, detecting a swipe gesture; 
 in accordance with a determination that the swipe gesture is an upward swipe, closing a first application and removing a representation of the first application from the open-application-selection user interface; and, 
 in accordance with a determination that the swipe gesture is a right to left swipe gesture, moving the representations of the plurality of open applications in accordance with the swipe gesture. 
 
     
     
       7. The method of  claim 1 , wherein performing a first operation within the application includes performing a page switching operation within the application. 
     
     
       8. The method of  claim 1 , wherein performing a first operation within the application includes navigating within a hierarchy associated with the application. 
     
     
       9. The method of  claim 1 , wherein performing a first operation within the application includes performing a preview operation within the application. 
     
     
       10. The method of  claim 1 , wherein performing a first operation within the application includes performing a menu-display operation within the application. 
     
     
       11. A non-transitory computer readable storage medium storing one or more programs, the one or more programs comprising instructions, which when executed by an electronic device with a touch-sensitive display and one or more sensors to detect intensities of contacts with the touch-sensitive display, cause the device to:
 displaying, on the touch-sensitive display, a user interface of an application; 
 while displaying the user interface of the application on the touch-sensitive display, detecting an input that includes detecting a contact at a first location on the touch-sensitive display, wherein the first location corresponds to a first operation within the application, wherein the contact remains stationary at the first location prior to lift-off of the first contact, and wherein the touch-sensitive display includes an open-application-selection region; and, 
 in response to detecting the input on the touch-sensitive display:
 in accordance with a determination that the input occurred inside of the open-application-selection region and that the input meets intensity criteria, including a criterion that is met when the input includes an increase in intensity of the contact above a first intensity threshold, perform a system function that is independent of the application without performing the first operation within the application, wherein performing the system function includes displaying an open-application-selection user interface that includes representations of a plurality of open applications, including one or more representations of open applications that were not displayed prior to detecting the input on the touch-sensitive display; and 
 in accordance with a determination that the input occurred inside of the open-application-selection region and that the input does not meet the intensity criteria, perform the first operation within the application based on the input without performing the system function, wherein performing the first operation includes changing the user interface of the application without displaying the open-application-selection user interface. 
 
 
     
     
       12. The non-transitory computer readable storage medium of  claim 11 , including instructions, which when executed by the electronic device with the touch-sensitive display and the one or more sensors, cause the electronic device to:
 in accordance with a determination that the input occurred outside of the open-application-selection region, perform an operation within the application based on the input. 
 
     
     
       13. The non-transitory computer readable storage medium of  claim 11 , wherein the open-application-selection user interface includes snapshots of open applications displayed in an overlapping 3D arrangement. 
     
     
       14. The non-transitory computer readable storage medium of  claim 11 , wherein the open-application-selection user interface includes snapshots of open applications. 
     
     
       15. The non-transitory computer readable storage medium of  claim 11 , wherein the open-application-selection region is on a portion of the display that, prior to detecting the input, includes the user interface of the application. 
     
     
       16. The non-transitory computer readable storage medium of  claim 11 , including instructions, which when executed by the electronic device with the touch-sensitive display and the one or more sensors, cause the electronic device to:
 while displaying the open-application-selection user interface, detect a swipe gesture; 
 in accordance with a determination that the swipe gesture is an upward swipe, close a first application and remove a representation of the first application from the open-application-selection user interface; and, 
 in accordance with a determination that the swipe gesture is a right to left swipe gesture, move the representations of the plurality of open applications in accordance with the swipe gesture. 
 
     
     
       17. The non-transitory computer readable storage medium of  claim 11 , wherein performing a first operation within the application includes performing a page switching operation within the application. 
     
     
       18. The non-transitory computer readable storage medium of  claim 11 , wherein performing a first operation within the application includes navigating within a hierarchy associated with the application. 
     
     
       19. The non-transitory computer readable storage medium of  claim 11 , wherein performing a first operation within the application includes performing a preview operation within the application. 
     
     
       20. The non-transitory computer readable storage medium of  claim 11 , wherein performing a first operation within the application includes performing a menu-display operation within the application. 
     
     
       21. An electronic device, comprising:
 a touch-sensitive display; 
 one or more sensors to detect intensities of contacts with the touch-sensitive display; 
 one or more processors; 
 memory; and 
 one or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, the one or more programs including instructions for:
 displaying, on the touch-sensitive display, a user interface of an application; 
 while displaying the user interface of the application on the touch-sensitive display, detecting an input that includes detecting a contact at a first location on the touch-sensitive display, wherein the first location corresponds to a first operation within the application, wherein the contact remains stationary at the first location prior to lift-off of the first contact, and wherein the touch-sensitive display includes an open-application-selection region; and, 
 in response to detecting the input on the touch-sensitive display:
 in accordance with a determination that the input occurred inside of the open-application-selection region and that the input meets intensity criteria, including a criterion that is met when the input includes an increase in intensity of the contact above a first intensity threshold, performing a system function that is independent of the application without performing the first operation within the application, wherein performing the system function includes displaying an open-application-selection user interface that includes representations of a plurality of open applications, including one or more representations of open applications that were not displayed prior to detecting the input on the touch-sensitive display; and 
 in accordance with a determination that the input occurred inside of the open-application-selection region and that the input does not meet the intensity criteria, performing the first operation within the application based on the input without performing the system function, wherein performing the first operation includes changing the user interface of the application without displaying the open-application-selection user interface. 
 
 
 
     
     
       22. The electronic device of  claim 21 , including instructions for:
 in accordance with a determination that the input occurred outside of the open-application-selection region, performing an operation within the application based on the input. 
 
     
     
       23. The electronic device of  claim 21 , wherein the open-application-selection user interface includes snapshots of open applications displayed in an overlapping 3D arrangement. 
     
     
       24. The electronic device of  claim 21 , wherein the open-application-selection user interface includes snapshots of open applications. 
     
     
       25. The electronic device of  claim 21 , wherein the open-application-selection region is on a portion of the display that, prior to detecting the input, includes the user interface of the application. 
     
     
       26. The electronic device of  claim 21 , including instructions for:
 while displaying the open-application-selection user interface, detecting a swipe gesture; 
 in accordance with a determination that the swipe gesture is an upward swipe, closing a first application and removing a representation of the first application from the open-application-selection user interface; and, 
 in accordance with a determination that the swipe gesture is a right to left swipe gesture, moving the representations of the plurality of open applications in accordance with the swipe gesture. 
 
     
     
       27. The electronic device of  claim 21 , wherein performing a first operation within the application includes performing a page switching operation within the application. 
     
     
       28. The electronic device of  claim 21 , wherein performing a first operation within the application includes navigating within a hierarchy associated with the application. 
     
     
       29. The electronic device of  claim 21 , wherein performing a first operation within the application includes performing a preview operation within the application. 
     
     
       30. The electronic device of  claim 21 , wherein performing a first operation within the application includes performing a menu-display operation within the application.

Description:
RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 14/866,511, filed Sep. 25, 2015, which claims priority to U.S. Provisional Application Ser. No. 62/215,696, filed Sep. 8, 2015, entitled “Devices and Methods for Navigating Between User Interfaces”; U.S. Provisional Application Ser. No. 62/213,606, filed Sep. 2, 2015, entitled “Devices and Methods for Navigating Between User Interfaces”; and to U.S. Provisional Application Ser. No. 62/172,226, filed Jun. 7, 2015, entitled “Devices and Methods for Navigating Between User Interfaces,” all of which are incorporated by reference herein in their entireties. 
    
    
     TECHNICAL FIELD 
     This relates generally to electronic devices with touch-sensitive surfaces, including but not limited to electronic devices with touch-sensitive surfaces that detect inputs for navigating between user interfaces. 
     BACKGROUND 
     The use of touch-sensitive surfaces as input devices for computers and other electronic computing devices has increased significantly in recent years. Exemplary touch-sensitive surfaces include touchpads and touch-screen displays. Such surfaces are widely used to navigate between related and unrelated user interfaces (e.g., between user interfaces for different applications and/or within a hierarchy of user interfaces within a single application). 
     Exemplary user interface hierarchies include groups of related user interfaces used for: organizing files and applications; storing and/or displaying digital images, editable documents (e.g., word processing, spreadsheet, and presentation documents), and/or non-editable documents (e.g., secured files and/or .pdf documents); recording and/or playing video and/or music; text-based communication (e.g., e-mail, texts, tweets, and social networking); voice and/or video communication (e.g., phone calls and video conferencing); and web browsing. A user will, in some circumstances, need to perform such user interface navigations within or between a file management program (e.g., Finder from Apple Inc. of Cupertino, Calif.), an image management application (e.g., Photos from Apple Inc. of Cupertino, Calif.), a digital content (e.g., videos and music) management application (e.g., iTunes from Apple Inc. of Cupertino, Calif.), a drawing application, a presentation application (e.g., Keynote from Apple Inc. of Cupertino, Calif.), a word processing application (e.g., Pages from Apple Inc. of Cupertino, Calif.), or a spreadsheet application (e.g., Numbers from Apple Inc. of Cupertino, Calif.). 
     But methods for performing these navigations and animating the transition between related user interfaces in a user interface hierarchy are cumbersome and inefficient. In addition, these methods take longer than necessary, thereby wasting energy. This latter consideration is particularly important in battery-operated devices. 
     Additionally, abrupt transitions between different user interfaces can be distracting and jarring for users, reducing the efficiency and enjoyment of the user when using the device. 
     SUMMARY 
     Accordingly, there is a need for electronic devices with faster, more efficient methods and interfaces for navigating between user interfaces. Such methods and interfaces optionally complement or replace conventional methods for navigating between user interfaces. Such methods and interfaces reduce the number, extent, and/or nature of the inputs from a user and produce a more efficient human-machine interface. For battery-operated devices, such methods and interfaces conserve power and increase the time between battery charges. 
     The above deficiencies and other problems associated with user interfaces for electronic devices with touch-sensitive surfaces are reduced or eliminated by the disclosed devices. In some embodiments, the device is a desktop computer. In some embodiments, the device is portable (e.g., a notebook computer, tablet computer, or handheld device). In some embodiments, the device is a personal electronic device (e.g., a wearable electronic device, such as a watch). In some embodiments, the device has a touchpad. In some embodiments, the device has a touch-sensitive display (also known as a “touch screen” or “touch-screen display”). In some embodiments, the device has a graphical user interface (GUI), one or more processors, memory and one or more modules, programs or sets of instructions stored in the memory for performing multiple functions. In some embodiments, the user interacts with the GUI primarily through stylus and/or finger contacts and gestures on the touch-sensitive surface. In some embodiments, the functions optionally include image editing, drawing, presenting, word processing, spreadsheet making, game playing, telephoning, video conferencing, e-mailing, instant messaging, workout support, digital photographing, digital videoing, web browsing, digital music playing, note taking, and/or digital video playing. Executable instructions for performing these functions are, optionally, included in a non-transitory computer readable storage medium or other computer program product configured for execution by one or more processors. 
     In accordance with some embodiments, a method is performed at an electronic device with a display and a touch-sensitive surface. The method includes: displaying a plurality of user interface representations in a stack on the display. At least a first user interface representation and a second user interface representation disposed above the first user interface representation in the stack, are visible on the display. The second user interface representation is offset from the first user interface representation in a first direction. The second user interface representation partially exposes the first user interface representation. The method further includes detecting a first drag gesture by a first contact at a location on the touch-sensitive surface that corresponds to a location of the first user interface representation on the display, the first contact moving across the touch-sensitive surface in a direction that corresponds to the first direction on the display. The method also includes, while the first contact is at a location on the touch-sensitive surface that corresponds to the location of the first user interface representation on the display and moving across the touch-sensitive surface in a direction that corresponds to the first direction on the display: moving the first user interface representation in the first direction on the display at a first speed in accordance with a speed of the first contact on the touch-sensitive surface, and moving the second user interface representation, disposed above the first user interface representation, in the first direction at a second speed greater than the first speed. 
     In accordance with some embodiments, a method is performed at an electronic device with a display, a touch-sensitive surface, and one or more sensors to detect intensity of contacts with the touch-sensitive surface. The method includes: displaying a first user interface on the display. The method further includes, while displaying the first user interface on the display, detecting an input by a first contact on the touch-sensitive surface. The method also includes, while detecting the input by the first contact, displaying a first user interface representation and at least a second user interface representation on the display. The method also includes while displaying the first user interface representation and at least the second user interface representation on the display, detecting termination of the input by the first contact. In response to detecting termination of the input by the first contact: in accordance with a determination that the first contact had a characteristic intensity during the input that was below a predetermined intensity threshold and the first contact moved during the input in a direction across the touch-sensitive surface that corresponds to a predefined direction on the display, displaying a second user interface that corresponds to the second user interface representation; and in accordance with a determination that the first contact had a characteristic intensity during the input that was below the predetermined intensity threshold and the first contact did not move during the input in a direction across the touch-sensitive surface that corresponds to the predefined direction on the display, redisplaying the first user interface. 
     In accordance with some embodiments, a method is performed at an electronic device with a display, a touch-sensitive surface, and one or more sensors to detect intensity of contacts with the touch-sensitive surface. The method includes: displaying a first user interface on the display. The method further includes, while displaying the first user interface on the display, detecting, on the touch-sensitive surface, an input by a first contact that includes a period of increasing intensity of the first contact. The method also includes, in response to detecting the input by the first contact that includes the period of increasing intensity of the first contact, displaying a first user interface representation for the first user interface and a second user interface representation for a second user interface on the display, where the first user interface representation is displayed over the second user interface representation and partially exposes the second user interface representation. The method also includes, while displaying the first user interface representation and the second user interface representation on the display, detecting that, during the period of increasing intensity of the first contact, the intensity of the first contact meets one or more predetermined intensity criteria. The method further includes, in response to detecting that the intensity of the first contact meets the one or more predetermined intensity criteria: ceasing to display the first user interface representation and the second user interface representation on the display, and displaying the second user interface on the display. 
     In accordance with some embodiments, a method is performed at an electronic device with a display, a touch-sensitive surface, and one or more sensors to detect intensity of contacts with the touch-sensitive surface. The method includes: displaying a plurality of user interface representations in a stack on the display. At least a first user interface representation, a second user interface representation, and a third user interface representation are visible on the display. The first user interface representation is laterally offset from the second user interface representation in a first direction and partially exposes the second user interface representation. The second user interface representation is laterally offset from the third user interface representation in the first direction and partially exposes the third user interface representation. The method further includes detecting an input by a first contact on the touch-sensitive surface at a location that corresponds to the second user interface representation on the display. The method also includes, in accordance with detecting an increase in intensity of the first contact on the touch-sensitive surface at the location that corresponds to the second user interface representation on the display, increasing an area of the second user interface representation that is exposed from behind the first user interface representation by increasing the lateral offset between the first user interface representation and the second user interface representation. 
     In accordance with some embodiments, a method is performed at an electronic device with a display and a touch-sensitive surface. The method includes: displaying a plurality of user interface representations in a stack on the display. At least a first user interface representation, a second user interface representation, and a third user interface representation are visible on the display. The second user interface representation is laterally offset from the first user interface representation in a first direction and partially exposes the first user interface representation. The third user interface representation is laterally offset from the second user interface representation in the first direction and partially exposes the second user interface representation. The method further includes detecting a drag gesture by a first contact that moves across the touch-sensitive surface, where movement of the drag gesture by the first contact corresponds to movement across one or more of the user interface representations in the stack. The method also includes, during the drag gesture, when the first contact moves over a location on the touch-sensitive surface that corresponds to the first user interface representation on the display, revealing more of the first user interface representation from behind the second user interface representation on the display. 
     In accordance with some embodiments, a method is performed at an electronic device with a display, a touch-sensitive surface, and one or more sensors to detect intensity of contacts with the touch-sensitive surface. The method includes: displaying a first user interface of a first application on the display, the first user interface including a backwards navigation control. The method further includes, while displaying the first user interface of the first application on the display, detecting a gesture by a first contact on the touch-sensitive surface at a location that corresponds to the backwards navigation control on the display. The method also includes, in response to detecting the gesture by the first contact on the touch-sensitive surface at a location that corresponds to the backwards navigation control: in accordance with a determination that the gesture by the first contact is a gesture with an intensity of the first contact that meets one or more predetermined intensity criteria, replacing display of the first user interface of the first application with display of a plurality of representations of user interfaces of the first application, including a representation of the first user interface and a representation of a second user interface; and, in accordance with a determination that the gesture by the first contact is a gesture with an intensity of the first contact that does not meet the one or more predetermined intensity criteria, replacing display of the first user interface of the first application with display of the second user interface of the first application. 
     In accordance with some embodiments, a method is performed at an electronic device with a display, a touch-sensitive surface, and one or more sensors to detect intensity of contacts with the touch-sensitive surface. The method includes: displaying, on the display, a user interface for an application; detecting an edge input that includes detecting a change in a characteristic intensity of a contact proximate to an edge of the touch-sensitive surface; and, in response to detecting the edge input: in accordance with a determination that the edge input meets system-gesture criteria, performing an operation that is independent of the application, wherein: the system-gesture criteria include intensity criteria; the system-gesture criteria include a location criterion that is met when the intensity criteria for the contact are met while the contact is within a first region relative to the touch-sensitive surface; and the first region relative to the touch-sensitive surface is determined based on one or more characteristics of the contact. 
     In accordance with some embodiments, a method is performed at an electronic device with a display, a touch-sensitive surface, and one or more sensors to detect intensity of contacts with the touch-sensitive surface. The method includes: displaying, on the display, a first view of a first application; while displaying the first view, detecting a first portion of a first input that includes detecting a first contact on the touch-sensitive surface; in response to detecting the first portion of the first input, in accordance with a determination that the first portion of the first input meets application-switching criteria, concurrently displaying, on the display, portions of a plurality of application views including the first application view and a second application view; while concurrently displaying the portions of the plurality of application views, detecting a second portion of the first input that includes liftoff of the first contact; and in response to detecting the second portion of the first input that includes liftoff of the first contact: in accordance with a determination that the second portion of the first input meets first-view display criteria, wherein the first-view display criteria include a criterion that is met when the liftoff of the first contact is detected in a first region of the touch-sensitive surface, ceasing to display the portion of the second application view and displaying the first application view on the display; and in accordance with a determination that the second portion of the first input meets multi-view display criteria, wherein the multi-view display criteria includes a criterion that is met when the liftoff of the first contact is detected in a second region of the touch-sensitive surface that is different from the first region of the touch-sensitive surface, maintaining concurrent display of at least a portion of the first application view and at least a portion of the second application view on the display after detecting the liftoff of the first contact. 
     In accordance with some embodiments, an electronic device includes a display unit configured to display a user interface, a touch-sensitive surface unit to receive contacts, and a processing unit coupled with the display unit and the touch-sensitive surface unit. The processing unit is configured to: enable display of a plurality of user interface representations in a stack on the display unit. At least a first user interface representation and a second user interface representation disposed above the first user interface representation in the stack, are visible on the display unit. The second user interface representation is offset from the first user interface representation in a first direction. The second user interface representation partially exposes the first user interface representation. The processing unit is further configured to detect a first drag gesture by a first contact at a location on the touch-sensitive surface unit that corresponds to a location of the first user interface representation on the display unit, the first contact moving across the touch-sensitive surface unit in a direction that corresponds to the first direction on the display unit. The processing unit is also configured to, while the first contact is at a location on the touch-sensitive surface unit that corresponds to the location of the first user interface representation on the display unit and moving across the touch-sensitive surface unit in a direction that corresponds to the first direction on the display unit: move the first user interface representation in the first direction on the display unit at a first speed in accordance with a speed of the first contact on the touch-sensitive surface unit; and move the second user interface representation, disposed above the first user interface representation, in the first direction at a second speed greater than the first speed. 
     In accordance with some embodiments, an electronic device includes a display unit configured to display a user interface, a touch-sensitive surface unit to receive contacts, one or more sensor units to detect intensity of contacts with the touch-sensitive surface unit; and a processing unit coupled with the display unit, the touch-sensitive surface unit, and the one or more sensor units. The processing unit is configured to: enable display a first user interface on the display unit. The processing unit is further configured to, while displaying the first user interface on the display unit, detect an input by a first contact on the touch-sensitive surface unit. The processing unit is also configured to, while detecting the input by the first contact, enable display of a first user interface representation and at least a second user interface representation on the display unit. The processing unit is further configured to, while displaying the first user interface representation and at least the second user interface representation on the display unit, detect termination of the input by the first contact. The processing unit is also configured to, in response to detecting termination of the input by the first contact: in accordance with a determination that the first contact had a characteristic intensity during the input that was below a predetermined intensity threshold and the first contact moved during the input in a direction across the touch-sensitive surface that corresponds to a predefined direction on the display, enable display of a second user interface that corresponds to the second user interface representation; and, in accordance with a determination that the first contact had a characteristic intensity during the input that was below the predetermined intensity threshold and the first contact did not move during the input in a direction across the touch-sensitive surface that corresponds to the predefined direction on the display, enable redisplay of the first user interface. 
     In accordance with some embodiments, an electronic device includes a display unit configured to display a user interface, a touch-sensitive surface unit to receive contacts, one or more sensor units to detect intensity of contacts with the touch-sensitive surface unit; and a processing unit coupled with the display unit, the touch-sensitive surface unit, and the one or more sensor units. The processing unit is configured to: enable display of a first user interface on the display unit. The processing unit is further configured to, while displaying the first user interface on the display unit, detect, on the touch-sensitive surface unit, an input by a first contact that includes a period of increasing intensity of the first contact. The processing unit is also configured to, in response to detecting the input by the first contact that includes the period of increasing intensity of the first contact: enable display of a first user interface representation for the first user interface and a second user interface representation for a second user interface on the display unit, where the first user interface representation is displayed over the second user interface representation and partially exposes the second user interface representation. The processing unit is further configured to, while displaying the first user interface representation and the second user interface representation on the display unit, detect that, during the period of increasing intensity of the first contact, the intensity of the first contact meets one or more predetermined intensity criteria. The processing unit is also configures to, in response to detecting that the intensity of the first contact meets the one or more predetermined intensity criteria: cease to enable display of the first user interface representation and the second user interface representation on the display unit, and enable display of the second user interface on the display. 
     In accordance with some embodiments, an electronic device includes a display unit configured to display a user interface, a touch-sensitive surface unit to receive contacts, one or more sensor units to detect intensity of contacts with the touch-sensitive surface unit; and a processing unit coupled with the display unit, the touch-sensitive surface unit, and the one or more sensor units. The processing unit is configured to: enable display of a plurality of user interface representations in a stack on the display unit. At least a first user interface representation, a second user interface representation, and a third user interface representation are visible on the display unit. The first user interface representation is laterally offset from the second user interface representation in a first direction and partially exposes the second user interface representation. The second user interface representation is laterally offset from the third user interface representation in the first direction and partially exposes the third user interface representation. The processing unit is further configured to detect an input by a first contact on the touch-sensitive surface unit at a location that corresponds to the second user interface representation on the display unit. The processing unit is also configured to, in accordance with detecting an increase in intensity of the first contact on the touch-sensitive surface unit at the location that corresponds to the second user interface representation on the display unit, increasing an area of the second user interface representation that is exposed from behind the first user interface representation by increasing the lateral offset between the first user interface representation and the second user interface representation. 
     In accordance with some embodiments, an electronic device includes a display unit configured to display a user interface, a touch-sensitive surface unit to receive contacts, one or more sensor units to detect intensity of contacts with the touch-sensitive surface unit; and a processing unit coupled with the display unit, the touch-sensitive surface unit, and the one or more sensor units. The processing unit is configured to: enable display of a plurality of user interface representations in a stack on the display unit. At least a first user interface representation, a second user interface representation, and a third user interface representation are visible on the display unit. The second user interface representation is laterally offset from the first user interface representation in a first direction and partially exposes the first user interface representation. The third user interface representation is laterally offset from the second user interface representation in the first direction and partially exposes the second user interface representation. The processing unit is further configured to detect a drag gesture by a first contact that moves across the touch-sensitive surface unit, where movement of the drag gesture by the first contact corresponds to movement across one or more of the user interface representations in the stack. The processing unit is also configured to, during the drag gesture, when the first contact moves over a location on the touch-sensitive surface unit that corresponds to the first user interface representation on the display unit, reveal more of the first user interface representation from behind the second user interface representation on the display unit. 
     In accordance with some embodiments, an electronic device includes a display unit configured to display a user interface, a touch-sensitive surface unit to receive contacts, one or more sensor units to detect intensity of contacts with the touch-sensitive surface unit; and a processing unit coupled with the display unit, the touch-sensitive surface unit, and the one or more sensor units. The processing unit is configured to: enable display a first user interface of a first application on the display unit, the first user interface including a backwards navigation control. The processing unit is further configured to, while displaying the first user interface of the first application on the display unit, detect a gesture by a first contact on the touch-sensitive surface unit at a location that corresponds to the backwards navigation control on the display unit. The processing unit is also configured to, in response to detecting the gesture by the first contact on the touch-sensitive surface unit at a location that corresponds to the backwards navigation control: in accordance with a determination that the gesture by the first contact is a gesture with an intensity of the first contact that meets one or more predetermined intensity criteria, replace display of the first user interface of the first application with display of a plurality of representations of user interfaces of the first application, including a representation of the first user interface and a representation of a second user interface; and, in accordance with a determination that the gesture by the first contact is a gesture with an intensity of the first contact that does not meet the one or more predetermined intensity criteria, replace display of the first user interface of the first application with display of the second user interface of the first application. 
     In accordance with some embodiments, an electronic device includes a display, a touch-sensitive surface, optionally one or more sensors to detect intensity of contacts with the touch-sensitive surface, one or more processors, memory, and one or more programs; the one or more programs are stored in the memory and configured to be executed by the one or more processors and the one or more programs include instructions for performing or causing performance of the operations of any of the methods described herein. In accordance with some embodiments, a computer readable storage medium has stored therein instructions which when executed by an electronic device with a display, a touch-sensitive surface, and optionally one or more sensors to detect intensity of contacts with the touch-sensitive surface, cause the device to perform or cause performance of the operations of any of the methods described herein. In accordance with some embodiments, a graphical user interface on an electronic device with a display, a touch-sensitive surface, optionally one or more sensors to detect intensity of contacts with the touch-sensitive surface, a memory, and one or more processors to execute one or more programs stored in the memory includes one or more of the elements displayed in any of the methods described herein, which are updated in response to inputs, as described in any of the methods described herein. In accordance with some embodiments, an electronic device includes: a display, a touch-sensitive surface, and optionally one or more sensors to detect intensity of contacts with the touch-sensitive surface; and means for performing or causing performance of the operations of any of the methods described herein. In accordance with some embodiments, an information processing apparatus, for use in an electronic device with a display and a touch-sensitive surface, and optionally one or more sensors to detect intensity of contacts with the touch-sensitive surface, includes means for performing or causing performance of the operations of any of the methods described herein. 
     In accordance with some embodiments, an electronic device includes a display unit configured to display content items, a touch-sensitive surface unit configured to receive user inputs, one or more sensor units configured to detect intensity of contacts with the touch-sensitive surface unit, and a processing unit coupled to the display unit, the touch-sensitive surface unit and the one or more sensor units. The processing unit is configured to: enable display, on the display, of a user interface for an application; detect an edge input that includes detecting a change in a characteristic intensity of a contact proximate to an edge of the touch-sensitive surface; and, in response to detecting the edge input: in accordance with a determination that the edge input meets system-gesture criteria, perform an operation that is independent of the application, wherein: the system-gesture criteria include intensity criteria; the system-gesture criteria include a location criterion that is met when the intensity criteria for the contact are met while the contact is within a first region relative to the touch-sensitive surface; and the first region relative to the touch-sensitive surface is determined based on one or more characteristics of the contact. 
     In accordance with some embodiments, an electronic device includes a display unit configured to display content items, a touch-sensitive surface unit configured to receive user inputs, one or more sensor units configured to detect intensity of contacts with the touch-sensitive surface unit, and a processing unit coupled to the display unit, the touch-sensitive surface unit and the one or more sensor units. The processing unit is configured to: enable display, on the display, of a first view of a first application; while enabling display of the first view, detect a first portion of a first input that includes detecting a first contact on the touch-sensitive surface; in response to detecting the first portion of the first input, in accordance with a determination that the first portion of the first input meets application-switching criteria, enable concurrent display, on the display, of portions of a plurality of application views including the first application view and a second application view; while enabling concurrent display of the portions of the plurality of application views, detect a second portion of the first input that includes liftoff of the first contact; and in response to detecting the second portion of the first input that includes liftoff of the first contact: in accordance with a determination that the second portion of the first input meets first-view display criteria, wherein the first-view display criteria include a criterion that is met when the liftoff of the first contact is detected in a first region of the touch-sensitive surface, cease to enable display of the portion of the second application view and enable display of the first application view on the display; and in accordance with a determination that the second portion of the first input meets multi-view display criteria, wherein the multi-view display criteria includes a criterion that is met when the liftoff of the first contact is detected in a second region of the touch-sensitive surface that is different from the first region of the touch-sensitive surface, maintain concurrent display of at least a portion of the first application view and at least a portion of the second application view on the display after detecting the liftoff of the first contact. 
     Thus, electronic devices with displays, touch-sensitive surfaces and optionally one or more sensors to detect intensity of contacts with the touch-sensitive surface are provided with faster, more efficient methods and interfaces for navigating between user interfaces, thereby increasing the effectiveness, efficiency, and user satisfaction with such devices. Such methods and interfaces may complement or replace conventional methods for navigating between user interfaces. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a better understanding of the various described embodiments, reference should be made to the Description of Embodiments below, in conjunction with the following drawings in which like reference numerals refer to corresponding parts throughout the figures. 
         FIG. 1A  is a block diagram illustrating a portable multifunction device with a touch-sensitive display in accordance with some embodiments. 
         FIG. 1B  is a block diagram illustrating exemplary components for event handling in accordance with some embodiments. 
         FIG. 2  illustrates a portable multifunction device having a touch screen in accordance with some embodiments. 
         FIG. 3  is a block diagram of an exemplary multifunction device with a display and a touch-sensitive surface in accordance with some embodiments. 
         FIG. 4A  illustrates an exemplary user interface for a menu of applications on a portable multifunction device in accordance with some embodiments. 
         FIG. 4B  illustrates an exemplary user interface for a multifunction device with a touch-sensitive surface that is separate from the display in accordance with some embodiments. 
         FIGS. 4C-4E  illustrate exemplary dynamic intensity thresholds in accordance with some embodiments. 
         FIGS. 5A-5HH  illustrate exemplary user interfaces for navigating between user interface representations in a user interface selection mode in accordance with some embodiments. 
         FIGS. 6A-6V  illustrate exemplary user interfaces for navigating between a displayed user interface and previously displayed user interfaces in accordance with some embodiments. 
         FIGS. 7A-7O  illustrate exemplary user interfaces for navigating between a displayed user interface and the user interface immediately preceding the displayed user interface in accordance with some embodiments. 
         FIGS. 8A-8R  illustrate exemplary user interfaces for navigating between user interface representations in a user interface selection mode in accordance with some embodiments. 
         FIGS. 9A-9H  illustrate exemplary user interfaces for navigating between user interface representations in a user interface selection mode in accordance with some embodiments. 
         FIGS. 10A-10H  are flow diagrams illustrating a method of navigating between user interface representations in a user interface selection mode in accordance with some embodiments. 
         FIGS. 11A-11E  are flow diagrams illustrating a method of navigating between a displayed user interface and previously displayed user interfaces in accordance with some embodiments. 
         FIGS. 12A-12E  are flow diagrams illustrating a method of navigating between a displayed user interface and the user interface immediately preceding the displayed user interface in accordance with some embodiments. 
         FIGS. 13A-13D  are flow diagrams illustrating a method of navigating between user interface representations in a user interface selection mode in accordance with some embodiments. 
         FIGS. 14A-14C  are flow diagrams illustrating a method of navigating between user interface representations in a user interface selection mode in accordance with some embodiments. 
         FIG. 15  is a flow diagram illustrating a method of navigating between user interfaces in a hierarchy of user interfaces for an application in accordance with some embodiments. 
         FIGS. 16-21  are functional block diagrams of electronic devices in accordance with some embodiments. 
         FIGS. 22A-22BA  illustrate exemplary user interfaces for invoking a user interface selection mode and for navigating between user interfaces in an application in accordance with some embodiments. 
         FIGS. 23A-23T  illustrate exemplary user interfaces for invoking a user interface selection mode and for navigating between user interfaces in an application in accordance with some embodiments. 
         FIGS. 24A-24F  are flow diagrams illustrating a method of invoking a user interface selection mode and for navigating between user interfaces in an application in accordance with some embodiments. 
         FIGS. 25A-25H  are flow diagrams illustrating a method of invoking a user interface selection mode and for navigating between user interfaces in an application in accordance with some embodiments. 
         FIGS. 26-27  are functional block diagrams of electronic devices in accordance with some embodiments. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Many electronic devices have graphical user interfaces for multiple different applications. A user commonly needs to access multiple different applications in succession. It is more efficient to maintain applications in an active state (e.g., open) when working in this fashion because it is time consuming and laborious to be opening and closing the same application multiple times a day. However, when multiple applications are open on an electronic device simultaneously, it can likewise be difficult to navigate through the open applications to identify and activate display of a desired application. Likewise, it is cumbersome to navigating through hierarchies with a large number of items (e.g., files, emails, previously displayed web pages, etc.) The present disclosure improves this processing by providing efficient and intuitive devices, methods, and user interfaces for navigating through representations of active applications and complex hierarchies. In some embodiments, the improvements are achieved by providing methods of navigating through a large number of items with fewer and smaller user inputs. In some embodiments, the improvements are achieved by incorporating heuristics based on sensing differences in the intensity of a contact, which does not require the user to make multiple user inputs, or even lift the contact away from a touch-sensitive surface to make a selection. 
     Below,  FIGS. 1A-1B, 2, and 3  provide a description of exemplary devices.  FIGS. 4A-4B, 5A-5HH, 6A-6V, 7A-7O, 8A-8R, 9A-9H, 22A-22BA, and 23A-23T  illustrate exemplary user interfaces for navigating between user interfaces.  FIGS. 10A-10H, 11A-11E, 12A-12E, 13A-13D, 14A-14C, 15, 24A-24F, and 25A-25H  are flow diagrams of methods of navigating between user interface representations. The user interfaces in  FIGS. 5A-5HH, 6A-6V, 7A-7O, 8A-8R, 9A-9H, 22A-22BA, and 23A-23T  are used to illustrate the processes in  FIGS. 10A-10H, 11A-11E, 12A-12E, 13A-13D, 14A-14C, 15, 24A-24F, and 25A-25H . 
     Exemplary Devices 
     Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the various described embodiments. However, it will be apparent to one of ordinary skill in the art that the various described embodiments may be practiced without these specific details. In other instances, well-known methods, procedures, components, circuits, and networks have not been described in detail so as not to unnecessarily obscure aspects of the embodiments. 
     It will also be understood that, although the terms first, second, etc. are, in some instances, used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first contact could be termed a second contact, and, similarly, a second contact could be termed a first contact, without departing from the scope of the various described embodiments. The first contact and the second contact are both contacts, but they are not the same contact, unless the context clearly indicates otherwise. 
     The terminology used in the description of the various described embodiments herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used in the description of the various described embodiments and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will also be understood that the term “and/or” as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items. It will be further understood that the terms “includes,” “including,” “comprises,” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
     As used herein, the term “if” is, optionally, construed to mean “when” or “upon” or “in response to determining” or “in response to detecting,” depending on the context. Similarly, the phrase “if it is determined” or “if [a stated condition or event] is detected” is, optionally, construed to mean “upon determining” or “in response to determining” or “upon detecting [the stated condition or event]” or “in response to detecting [the stated condition or event],” depending on the context. 
     Embodiments of electronic devices, user interfaces for such devices, and associated processes for using such devices are described. In some embodiments, the device is a portable communications device, such as a mobile telephone, that also contains other functions, such as PDA and/or music player functions. Exemplary embodiments of portable multifunction devices include, without limitation, the iPhone®, iPod Touch®, and iPad® devices from Apple Inc. of Cupertino, Calif. Other portable electronic devices, such as laptops or tablet computers with touch-sensitive surfaces (e.g., touch-screen displays and/or touchpads), are, optionally, used. It should also be understood that, in some embodiments, the device is not a portable communications device, but is a desktop computer with a touch-sensitive surface (e.g., a touch-screen display and/or a touchpad). 
     In the discussion that follows, an electronic device that includes a display and a touch-sensitive surface is described. It should be understood, however, that the electronic device optionally includes one or more other physical user-interface devices, such as a physical keyboard, a mouse and/or a joystick. 
     The device typically supports a variety of applications, such as one or more of the following: a note taking application, a drawing application, a presentation application, a word processing application, a website creation application, a disk authoring application, a spreadsheet application, a gaming application, a telephone application, a video conferencing application, an e-mail application, an instant messaging application, a workout support application, a photo management application, a digital camera application, a digital video camera application, a web browsing application, a digital music player application, and/or a digital video player application. 
     The various applications that are executed on the device optionally use at least one common physical user-interface device, such as the touch-sensitive surface. One or more functions of the touch-sensitive surface as well as corresponding information displayed on the device are, optionally, adjusted and/or varied from one application to the next and/or within a respective application. In this way, a common physical architecture (such as the touch-sensitive surface) of the device optionally supports the variety of applications with user interfaces that are intuitive and transparent to the user. 
     Attention is now directed toward embodiments of portable devices with touch-sensitive displays.  FIG. 1A  is a block diagram illustrating portable multifunction device  100  with touch-sensitive display system  112  in accordance with some embodiments. Touch-sensitive display system  112  is sometimes called a “touch screen” for convenience, and is sometimes simply called a touch-sensitive display. Device  100  includes memory  102  (which optionally includes one or more computer readable storage mediums), memory controller  122 , one or more processing units (CPUs)  120 , peripherals interface  118 , RF circuitry  108 , audio circuitry  110 , speaker  111 , microphone  113 , input/output (I/O) subsystem  106 , other input or control devices  116 , and external port  124 . Device  100  optionally includes one or more optical sensors  164 . Device  100  optionally includes one or more intensity sensors  165  for detecting intensity of contacts on device  100  (e.g., a touch-sensitive surface such as touch-sensitive display system  112  of device  100 ). Device  100  optionally includes one or more tactile output generators  167  for generating tactile outputs on device  100  (e.g., generating tactile outputs on a touch-sensitive surface such as touch-sensitive display system  112  of device  100  or touchpad  355  of device  300 ). These components optionally communicate over one or more communication buses or signal lines  103 . 
     As used in the specification and claims, the term “tactile output” refers to physical displacement of a device relative to a previous position of the device, physical displacement of a component (e.g., a touch-sensitive surface) of a device relative to another component (e.g., housing) of the device, or displacement of the component relative to a center of mass of the device that will be detected by a user with the user&#39;s sense of touch. For example, in situations where the device or the component of the device is in contact with a surface of a user that is sensitive to touch (e.g., a finger, palm, or other part of a user&#39;s hand), the tactile output generated by the physical displacement will be interpreted by the user as a tactile sensation corresponding to a perceived change in physical characteristics of the device or the component of the device. For example, movement of a touch-sensitive surface (e.g., a touch-sensitive display or trackpad) is, optionally, interpreted by the user as a “down click” or “up click” of a physical actuator button. In some cases, a user will feel a tactile sensation such as an “down click” or “up click” even when there is no movement of a physical actuator button associated with the touch-sensitive surface that is physically pressed (e.g., displaced) by the user&#39;s movements. As another example, movement of the touch-sensitive surface is, optionally, interpreted or sensed by the user as “roughness” of the touch-sensitive surface, even when there is no change in smoothness of the touch-sensitive surface. While such interpretations of touch by a user will be subject to the individualized sensory perceptions of the user, there are many sensory perceptions of touch that are common to a large majority of users. Thus, when a tactile output is described as corresponding to a particular sensory perception of a user (e.g., an “up click,” a “down click,” “roughness”), unless otherwise stated, the generated tactile output corresponds to physical displacement of the device or a component thereof that will generate the described sensory perception for a typical (or average) user. 
     It should be appreciated that device  100  is only one example of a portable multifunction device, and that device  100  optionally has more or fewer components than shown, optionally combines two or more components, or optionally has a different configuration or arrangement of the components. The various components shown in  FIG. 1A  are implemented in hardware, software, firmware, or a combination thereof, including one or more signal processing and/or application specific integrated circuits. 
     Memory  102  optionally includes high-speed random access memory and optionally also includes non-volatile memory, such as one or more magnetic disk storage devices, flash memory devices, or other non-volatile solid-state memory devices. Access to memory  102  by other components of device  100 , such as CPU(s)  120  and the peripherals interface  118 , is, optionally, controlled by memory controller  122 . 
     Peripherals interface  118  can be used to couple input and output peripherals of the device to CPU(s)  120  and memory  102 . The one or more processors  120  run or execute various software programs and/or sets of instructions stored in memory  102  to perform various functions for device  100  and to process data. 
     In some embodiments, peripherals interface  118 , CPU(s)  120 , and memory controller  122  are, optionally, implemented on a single chip, such as chip  104 . In some other embodiments, they are, optionally, implemented on separate chips. 
     RF (radio frequency) circuitry  108  receives and sends RF signals, also called electromagnetic signals. RF circuitry  108  converts electrical signals to/from electromagnetic signals and communicates with communications networks and other communications devices via the electromagnetic signals. RF circuitry  108  optionally includes well-known circuitry for performing these functions, including but not limited to an antenna system, an RF transceiver, one or more amplifiers, a tuner, one or more oscillators, a digital signal processor, a CODEC chipset, a subscriber identity module (SIM) card, memory, and so forth. RF circuitry  108  optionally communicates with networks, such as the Internet, also referred to as the World Wide Web (WWW), an intranet and/or a wireless network, such as a cellular telephone network, a wireless local area network (LAN) and/or a metropolitan area network (MAN), and other devices by wireless communication. The wireless communication optionally uses any of a plurality of communications standards, protocols and technologies, including but not limited to Global System for Mobile Communications (GSM), Enhanced Data GSM Environment (EDGE), high-speed downlink packet access (HSDPA), high-speed uplink packet access (HSDPA), Evolution, Data-Only (EV-DO), HSPA, HSPA+, Dual-Cell HSPA (DC-HSPDA), long term evolution (LTE), near field communication (NFC), wideband code division multiple access (W-CDMA), code division multiple access (CDMA), time division multiple access (TDMA), Bluetooth, Wireless Fidelity (Wi-Fi) (e.g., IEEE 802.11a, IEEE 802.11ac, IEEE 802.11ax, IEEE 802.11b, IEEE 802.11g and/or IEEE 802.11n), voice over Internet Protocol (VoIP), Wi-MAX, a protocol for e-mail (e.g., Internet message access protocol (IMAP) and/or post office protocol (POP)), instant messaging (e.g., extensible messaging and presence protocol (XMPP), Session Initiation Protocol for Instant Messaging and Presence Leveraging Extensions (SIMPLE), Instant Messaging and Presence Service (IMPS)), and/or Short Message Service (SMS), or any other suitable communication protocol, including communication protocols not yet developed as of the filing date of this document. 
     Audio circuitry  110 , speaker  111 , and microphone  113  provide an audio interface between a user and device  100 . Audio circuitry  110  receives audio data from peripherals interface  118 , converts the audio data to an electrical signal, and transmits the electrical signal to speaker  111 . Speaker  111  converts the electrical signal to human-audible sound waves. Audio circuitry  110  also receives electrical signals converted by microphone  113  from sound waves. Audio circuitry  110  converts the electrical signal to audio data and transmits the audio data to peripherals interface  118  for processing. Audio data is, optionally, retrieved from and/or transmitted to memory  102  and/or RF circuitry  108  by peripherals interface  118 . In some embodiments, audio circuitry  110  also includes a headset jack (e.g.,  212 ,  FIG. 2 ). The headset jack provides an interface between audio circuitry  110  and removable audio input/output peripherals, such as output-only headphones or a headset with both output (e.g., a headphone for one or both ears) and input (e.g., a microphone). 
     I/O subsystem  106  couples input/output peripherals on device  100 , such as touch-sensitive display system  112  and other input or control devices  116 , with peripherals interface  118 . I/O subsystem  106  optionally includes display controller  156 , optical sensor controller  158 , intensity sensor controller  159 , haptic feedback controller  161 , and one or more input controllers  160  for other input or control devices. The one or more input controllers  160  receive/send electrical signals from/to other input or control devices  116 . The other input or control devices  116  optionally include physical buttons (e.g., push buttons, rocker buttons, etc.), dials, slider switches, joysticks, click wheels, and so forth. In some alternate embodiments, input controller(s)  160  are, optionally, coupled with any (or none) of the following: a keyboard, infrared port, USB port, stylus, and/or a pointer device such as a mouse. The one or more buttons (e.g.,  208 ,  FIG. 2 ) optionally include an up/down button for volume control of speaker  111  and/or microphone  113 . The one or more buttons optionally include a push button (e.g.,  206 ,  FIG. 2 ). 
     Touch-sensitive display system  112  provides an input interface and an output interface between the device and a user. Display controller  156  receives and/or sends electrical signals from/to touch-sensitive display system  112 . Touch-sensitive display system  112  displays visual output to the user. The visual output optionally includes graphics, text, icons, video, and any combination thereof (collectively termed “graphics”). In some embodiments, some or all of the visual output corresponds to user-interface objects. As used herein, the term “affordance” refers to a user-interactive graphical user interface object (e.g., a graphical user interface object that is configured to respond to inputs directed toward the graphical user interface object). Examples of user-interactive graphical user interface objects include, without limitation, a button, slider, icon, selectable menu item, switch, hyperlink, or other user interface control. 
     Touch-sensitive display system  112  has a touch-sensitive surface, sensor or set of sensors that accepts input from the user based on haptic and/or tactile contact. Touch-sensitive display system  112  and display controller  156  (along with any associated modules and/or sets of instructions in memory  102 ) detect contact (and any movement or breaking of the contact) on touch-sensitive display system  112  and converts the detected contact into interaction with user-interface objects (e.g., one or more soft keys, icons, web pages or images) that are displayed on touch-sensitive display system  112 . In an exemplary embodiment, a point of contact between touch-sensitive display system  112  and the user corresponds to a finger of the user or a stylus. 
     Touch-sensitive display system  112  optionally uses LCD (liquid crystal display) technology, LPD (light emitting polymer display) technology, or LED (light emitting diode) technology, although other display technologies are used in other embodiments. Touch-sensitive display system  112  and display controller  156  optionally detect contact and any movement or breaking thereof using any of a plurality of touch sensing technologies now known or later developed, including but not limited to capacitive, resistive, infrared, and surface acoustic wave technologies, as well as other proximity sensor arrays or other elements for determining one or more points of contact with touch-sensitive display system  112 . In an exemplary embodiment, projected mutual capacitance sensing technology is used, such as that found in the iPhone®, iPod Touch®, and iPad® from Apple Inc. of Cupertino, Calif. 
     Touch-sensitive display system  112  optionally has a video resolution in excess of 100 dpi. In some embodiments, the touch screen video resolution is in excess of 400 dpi (e.g., 500 dpi, 800 dpi, or greater). The user optionally makes contact with touch-sensitive display system  112  using any suitable object or appendage, such as a stylus, a finger, and so forth. In some embodiments, the user interface is designed to work with finger-based contacts and gestures, which can be less precise than stylus-based input due to the larger area of contact of a finger on the touch screen. In some embodiments, the device translates the rough finger-based input into a precise pointer/cursor position or command for performing the actions desired by the user. 
     In some embodiments, in addition to the touch screen, device  100  optionally includes a touchpad (not shown) for activating or deactivating particular functions. In some embodiments, the touchpad is a touch-sensitive area of the device that, unlike the touch screen, does not display visual output. The touchpad is, optionally, a touch-sensitive surface that is separate from touch-sensitive display system  112  or an extension of the touch-sensitive surface formed by the touch screen. 
     Device  100  also includes power system  162  for powering the various components. Power system  162  optionally includes a power management system, one or more power sources (e.g., battery, alternating current (AC)), a recharging system, a power failure detection circuit, a power converter or inverter, a power status indicator (e.g., a light-emitting diode (LED)) and any other components associated with the generation, management and distribution of power in portable devices. 
     Device  100  optionally also includes one or more optical sensors  164 .  FIG. 1A  shows an optical sensor coupled with optical sensor controller  158  in I/O subsystem  106 . Optical sensor(s)  164  optionally include charge-coupled device (CCD) or complementary metal-oxide semiconductor (CMOS) phototransistors. Optical sensor(s)  164  receive light from the environment, projected through one or more lens, and converts the light to data representing an image. In conjunction with imaging module  143  (also called a camera module), optical sensor(s)  164  optionally capture still images and/or video. In some embodiments, an optical sensor is located on the back of device  100 , opposite touch-sensitive display system  112  on the front of the device, so that the touch screen is enabled for use as a viewfinder for still and/or video image acquisition. In some embodiments, another optical sensor is located on the front of the device so that the user&#39;s image is obtained (e.g., for selfies, for videoconferencing while the user views the other video conference participants on the touch screen, etc.). 
     Device  100  optionally also includes one or more contact intensity sensors  165 .  FIG. 1A  shows a contact intensity sensor coupled with intensity sensor controller  159  in I/O subsystem  106 . Contact intensity sensor(s)  165  optionally include one or more piezoresistive strain gauges, capacitive force sensors, electric force sensors, piezoelectric force sensors, optical force sensors, capacitive touch-sensitive surfaces, or other intensity sensors (e.g., sensors used to measure the force (or pressure) of a contact on a touch-sensitive surface). Contact intensity sensor(s)  165  receive contact intensity information (e.g., pressure information or a proxy for pressure information) from the environment. In some embodiments, at least one contact intensity sensor is collocated with, or proximate to, a touch-sensitive surface (e.g., touch-sensitive display system  112 ). In some embodiments, at least one contact intensity sensor is located on the back of device  100 , opposite touch-screen display system  112  which is located on the front of device  100 . 
     Device  100  optionally also includes one or more proximity sensors  166 .  FIG. 1A  shows proximity sensor  166  coupled with peripherals interface  118 . Alternately, proximity sensor  166  is coupled with input controller  160  in I/O subsystem  106 . In some embodiments, the proximity sensor turns off and disables touch-sensitive display system  112  when the multifunction device is placed near the user&#39;s ear (e.g., when the user is making a phone call). 
     Device  100  optionally also includes one or more tactile output generators  167 .  FIG. 1A  shows a tactile output generator coupled with haptic feedback controller  161  in I/O subsystem  106 . Tactile output generator(s)  167  optionally include one or more electroacoustic devices such as speakers or other audio components and/or electromechanical devices that convert energy into linear motion such as a motor, solenoid, electroactive polymer, piezoelectric actuator, electrostatic actuator, or other tactile output generating component (e.g., a component that converts electrical signals into tactile outputs on the device). Tactile output generator(s)  167  receive tactile feedback generation instructions from haptic feedback module  133  and generates tactile outputs on device  100  that are capable of being sensed by a user of device  100 . In some embodiments, at least one tactile output generator is collocated with, or proximate to, a touch-sensitive surface (e.g., touch-sensitive display system  112 ) and, optionally, generates a tactile output by moving the touch-sensitive surface vertically (e.g., in/out of a surface of device  100 ) or laterally (e.g., back and forth in the same plane as a surface of device  100 ). In some embodiments, at least one tactile output generator sensor is located on the back of device  100 , opposite touch-sensitive display system  112 , which is located on the front of device  100 . 
     Device  100  optionally also includes one or more accelerometers  168 .  FIG. 1A  shows accelerometer  168  coupled with peripherals interface  118 . Alternately, accelerometer  168  is, optionally, coupled with an input controller  160  in I/O subsystem  106 . In some embodiments, information is displayed on the touch-screen display in a portrait view or a landscape view based on an analysis of data received from the one or more accelerometers. Device  100  optionally includes, in addition to accelerometer(s)  168 , a magnetometer (not shown) and a GPS (or GLONASS or other global navigation system) receiver (not shown) for obtaining information concerning the location and orientation (e.g., portrait or landscape) of device  100 . 
     In some embodiments, the software components stored in memory  102  include operating system  126 , communication module (or set of instructions)  128 , contact/motion module (or set of instructions)  130 , graphics module (or set of instructions)  132 , haptic feedback module (or set of instructions)  133 , text input module (or set of instructions)  134 , Global Positioning System (GPS) module (or set of instructions)  135 , and applications (or sets of instructions)  136 . Furthermore, in some embodiments, memory  102  stores device/global internal state  157 , as shown in  FIGS. 1A and 3 . Device/global internal state  157  includes one or more of: active application state, indicating which applications, if any, are currently active; display state, indicating what applications, views or other information occupy various regions of touch-sensitive display system  112 ; sensor state, including information obtained from the device&#39;s various sensors and other input or control devices  116 ; and location and/or positional information concerning the device&#39;s location and/or attitude. 
     Operating system  126  (e.g., iOS, Darwin, RTXC, LINUX, UNIX, OS X, WINDOWS, or an embedded operating system such as VxWorks) includes various software components and/or drivers for controlling and managing general system tasks (e.g., memory management, storage device control, power management, etc.) and facilitates communication between various hardware and software components. 
     Communication module  128  facilitates communication with other devices over one or more external ports  124  and also includes various software components for handling data received by RF circuitry  108  and/or external port  124 . External port  124  (e.g., Universal Serial Bus (USB), FIREWIRE, etc.) is adapted for coupling directly to other devices or indirectly over a network (e.g., the Internet, wireless LAN, etc.). In some embodiments, the external port is a multi-pin (e.g., 30-pin) connector that is the same as, or similar to and/or compatible with the 30-pin connector used in some iPhone®, iPod Touch®, and iPad® devices from Apple Inc. of Cupertino, Calif. In some embodiments, the external port is a Lightning connector that is the same as, or similar to and/or compatible with the Lightning connector used in some iPhone®, iPod Touch®, and iPad® devices from Apple Inc. of Cupertino, Calif. 
     Contact/motion module  130  optionally detects contact with touch-sensitive display system  112  (in conjunction with display controller  156 ) and other touch-sensitive devices (e.g., a touchpad or physical click wheel). Contact/motion module  130  includes various software components for performing various operations related to detection of contact (e.g., by a finger or by a stylus), such as determining if contact has occurred (e.g., detecting a finger-down event), determining an intensity of the contact (e.g., the force or pressure of the contact or a substitute for the force or pressure of the contact), determining if there is movement of the contact and tracking the movement across the touch-sensitive surface (e.g., detecting one or more finger-dragging events), and determining if the contact has ceased (e.g., detecting a finger-up event or a break in contact). Contact/motion module  130  receives contact data from the touch-sensitive surface. Determining movement of the point of contact, which is represented by a series of contact data, optionally includes determining speed (magnitude), velocity (magnitude and direction), and/or an acceleration (a change in magnitude and/or direction) of the point of contact. These operations are, optionally, applied to single contacts (e.g., one finger contacts or stylus contacts) or to multiple simultaneous contacts (e.g., “multitouch”/multiple finger contacts). In some embodiments, contact/motion module  130  and display controller  156  detect contact on a touchpad. 
     Contact/motion module  130  optionally detects a gesture input by a user. Different gestures on the touch-sensitive surface have different contact patterns (e.g., different motions, timings, and/or intensities of detected contacts). Thus, a gesture is, optionally, detected by detecting a particular contact pattern. For example, detecting a finger tap gesture includes detecting a finger-down event followed by detecting a finger-up (lift off) event at the same position (or substantially the same position) as the finger-down event (e.g., at the position of an icon). As another example, detecting a finger swipe gesture on the touch-sensitive surface includes detecting a finger-down event followed by detecting one or more finger-dragging events, and subsequently followed by detecting a finger-up (lift off) event. Similarly, tap, swipe, drag, and other gestures are optionally detected for a stylus by detecting a particular contact pattern for the stylus. 
     Graphics module  132  includes various known software components for rendering and displaying graphics on touch-sensitive display system  112  or other display, including components for changing the visual impact (e.g., brightness, transparency, saturation, contrast or other visual property) of graphics that are displayed. As used herein, the term “graphics” includes any object that can be displayed to a user, including without limitation text, web pages, icons (such as user-interface objects including soft keys), digital images, videos, animations and the like. 
     In some embodiments, graphics module  132  stores data representing graphics to be used. Each graphic is, optionally, assigned a corresponding code. Graphics module  132  receives, from applications etc., one or more codes specifying graphics to be displayed along with, if necessary, coordinate data and other graphic property data, and then generates screen image data to output to display controller  156 . 
     Haptic feedback module  133  includes various software components for generating instructions used by tactile output generator(s)  167  to produce tactile outputs at one or more locations on device  100  in response to user interactions with device  100 . 
     Text input module  134 , which is, optionally, a component of graphics module  132 , provides soft keyboards for entering text in various applications (e.g., contacts  137 , e-mail  140 , IM  141 , browser  147 , and any other application that needs text input). 
     GPS module  135  determines the location of the device and provides this information for use in various applications (e.g., to telephone  138  for use in location-based dialing, to camera  143  as picture/video metadata, and to applications that provide location-based services such as weather widgets, local yellow page widgets, and map/navigation widgets). 
     Applications  136  optionally include the following modules (or sets of instructions), or a subset or superset thereof:
         contacts module  137  (sometimes called an address book or contact list);   telephone module  138 ;   video conferencing module  139 ;   e-mail client module  140 ;   instant messaging (IM) module  141 ;   workout support module  142 ;   camera module  143  for still and/or video images;   image management module  144 ;   browser module  147 ;   calendar module  148 ;   widget modules  149 , which optionally include one or more of: weather widget  149 - 1 , stocks widget  149 - 2 , calculator widget  149 - 3 , alarm clock widget  149 - 4 , dictionary widget  149 - 5 , and other widgets obtained by the user, as well as user-created widgets  149 - 6 ;   widget creator module  150  for making user-created widgets  149 - 6 ;   search module  151 ;   video and music player module  152 , which is, optionally, made up of a video player module and a music player module;   notes module  153 ;   map module  154 ; and/or   online video module  155 .       

     Examples of other applications  136  that are, optionally, stored in memory  102  include other word processing applications, other image editing applications, drawing applications, presentation applications, JAVA-enabled applications, encryption, digital rights management, voice recognition, and voice replication. 
     In conjunction with touch-sensitive display system  112 , display controller  156 , contact module  130 , graphics module  132 , and text input module  134 , contacts module  137  includes executable instructions to manage an address book or contact list (e.g., stored in application internal state  192  of contacts module  137  in memory  102  or memory  370 ), including: adding name(s) to the address book; deleting name(s) from the address book; associating telephone number(s), e-mail address(es), physical address(es) or other information with a name; associating an image with a name; categorizing and sorting names; providing telephone numbers and/or e-mail addresses to initiate and/or facilitate communications by telephone  138 , video conference  139 , e-mail  140 , or IM  141 ; and so forth. 
     In conjunction with RF circuitry  108 , audio circuitry  110 , speaker  111 , microphone  113 , touch-sensitive display system  112 , display controller  156 , contact module  130 , graphics module  132 , and text input module  134 , telephone module  138  includes executable instructions to enter a sequence of characters corresponding to a telephone number, access one or more telephone numbers in address book  137 , modify a telephone number that has been entered, dial a respective telephone number, conduct a conversation and disconnect or hang up when the conversation is completed. As noted above, the wireless communication optionally uses any of a plurality of communications standards, protocols and technologies. 
     In conjunction with RF circuitry  108 , audio circuitry  110 , speaker  111 , microphone  113 , touch-sensitive display system  112 , display controller  156 , optical sensor(s)  164 , optical sensor controller  158 , contact module  130 , graphics module  132 , text input module  134 , contact list  137 , and telephone module  138 , videoconferencing module  139  includes executable instructions to initiate, conduct, and terminate a video conference between a user and one or more other participants in accordance with user instructions. 
     In conjunction with RF circuitry  108 , touch-sensitive display system  112 , display controller  156 , contact module  130 , graphics module  132 , and text input module  134 , e-mail client module  140  includes executable instructions to create, send, receive, and manage e-mail in response to user instructions. In conjunction with image management module  144 , e-mail client module  140  makes it very easy to create and send e-mails with still or video images taken with camera module  143 . 
     In conjunction with RF circuitry  108 , touch-sensitive display system  112 , display controller  156 , contact module  130 , graphics module  132 , and text input module  134 , the instant messaging module  141  includes executable instructions to enter a sequence of characters corresponding to an instant message, to modify previously entered characters, to transmit a respective instant message (for example, using a Short Message Service (SMS) or Multimedia Message Service (MMS) protocol for telephony-based instant messages or using XIVIPP, SIMPLE, Apple Push Notification Service (APNs) or IMPS for Internet-based instant messages), to receive instant messages and to view received instant messages. In some embodiments, transmitted and/or received instant messages optionally include graphics, photos, audio files, video files and/or other attachments as are supported in a MMS and/or an Enhanced Messaging Service (EMS). As used herein, “instant messaging” refers to both telephony-based messages (e.g., messages sent using SMS or MMS) and Internet-based messages (e.g., messages sent using XMPP, SIMPLE, APNs, or IMPS). 
     In conjunction with RF circuitry  108 , touch-sensitive display system  112 , display controller  156 , contact module  130 , graphics module  132 , text input module  134 , GPS module  135 , map module  154 , and music player module  146 , workout support module  142  includes executable instructions to create workouts (e.g., with time, distance, and/or calorie burning goals); communicate with workout sensors (in sports devices and smart watches); receive workout sensor data; calibrate sensors used to monitor a workout; select and play music for a workout; and display, store and transmit workout data. 
     In conjunction with touch-sensitive display system  112 , display controller  156 , optical sensor(s)  164 , optical sensor controller  158 , contact module  130 , graphics module  132 , and image management module  144 , camera module  143  includes executable instructions to capture still images or video (including a video stream) and store them into memory  102 , modify characteristics of a still image or video, and/or delete a still image or video from memory  102 . 
     In conjunction with touch-sensitive display system  112 , display controller  156 , contact module  130 , graphics module  132 , text input module  134 , and camera module  143 , image management module  144  includes executable instructions to arrange, modify (e.g., edit), or otherwise manipulate, label, delete, present (e.g., in a digital slide show or album), and store still and/or video images. 
     In conjunction with RF circuitry  108 , touch-sensitive display system  112 , display system controller  156 , contact module  130 , graphics module  132 , and text input module  134 , browser module  147  includes executable instructions to browse the Internet in accordance with user instructions, including searching, linking to, receiving, and displaying web pages or portions thereof, as well as attachments and other files linked to web pages. 
     In conjunction with RF circuitry  108 , touch-sensitive display system  112 , display system controller  156 , contact module  130 , graphics module  132 , text input module  134 , e-mail client module  140 , and browser module  147 , calendar module  148  includes executable instructions to create, display, modify, and store calendars and data associated with calendars (e.g., calendar entries, to do lists, etc.) in accordance with user instructions. 
     In conjunction with RF circuitry  108 , touch-sensitive display system  112 , display system controller  156 , contact module  130 , graphics module  132 , text input module  134 , and browser module  147 , widget modules  149  are mini-applications that are, optionally, downloaded and used by a user (e.g., weather widget  149 - 1 , stocks widget  149 - 2 , calculator widget  149 - 3 , alarm clock widget  149 - 4 , and dictionary widget  149 - 5 ) or created by the user (e.g., user-created widget  149 - 6 ). In some embodiments, a widget includes an HTML (Hypertext Markup Language) file, a CSS (Cascading Style Sheets) file, and a JavaScript file. In some embodiments, a widget includes an XML (Extensible Markup Language) file and a JavaScript file (e.g., Yahoo! Widgets). 
     In conjunction with RF circuitry  108 , touch-sensitive display system  112 , display system controller  156 , contact module  130 , graphics module  132 , text input module  134 , and browser module  147 , the widget creator module  150  includes executable instructions to create widgets (e.g., turning a user-specified portion of a web page into a widget). 
     In conjunction with touch-sensitive display system  112 , display system controller  156 , contact module  130 , graphics module  132 , and text input module  134 , search module  151  includes executable instructions to search for text, music, sound, image, video, and/or other files in memory  102  that match one or more search criteria (e.g., one or more user-specified search terms) in accordance with user instructions. 
     In conjunction with touch-sensitive display system  112 , display system controller  156 , contact module  130 , graphics module  132 , audio circuitry  110 , speaker  111 , RF circuitry  108 , and browser module  147 , video and music player module  152  includes executable instructions that allow the user to download and play back recorded music and other sound files stored in one or more file formats, such as MP3 or AAC files, and executable instructions to display, present or otherwise play back videos (e.g., on touch-sensitive display system  112 , or on an external display connected wirelessly or via external port  124 ). In some embodiments, device  100  optionally includes the functionality of an MP3 player, such as an iPod (trademark of Apple Inc.). 
     In conjunction with touch-sensitive display system  112 , display controller  156 , contact module  130 , graphics module  132 , and text input module  134 , notes module  153  includes executable instructions to create and manage notes, to do lists, and the like in accordance with user instructions. 
     In conjunction with RF circuitry  108 , touch-sensitive display system  112 , display system controller  156 , contact module  130 , graphics module  132 , text input module  134 , GPS module  135 , and browser module  147 , map module  154  includes executable instructions to receive, display, modify, and store maps and data associated with maps (e.g., driving directions; data on stores and other points of interest at or near a particular location; and other location-based data) in accordance with user instructions. 
     In conjunction with touch-sensitive display system  112 , display system controller  156 , contact module  130 , graphics module  132 , audio circuitry  110 , speaker  111 , RF circuitry  108 , text input module  134 , e-mail client module  140 , and browser module  147 , online video module  155  includes executable instructions that allow the user to access, browse, receive (e.g., by streaming and/or download), play back (e.g., on the touch screen  112 , or on an external display connected wirelessly or via external port  124 ), send an e-mail with a link to a particular online video, and otherwise manage online videos in one or more file formats, such as H.264. In some embodiments, instant messaging module  141 , rather than e-mail client module  140 , is used to send a link to a particular online video. 
     Each of the above identified modules and applications correspond to a set of executable instructions for performing one or more functions described above and the methods described in this application (e.g., the computer-implemented methods and other information processing methods described herein). These modules (i.e., sets of instructions) need not be implemented as separate software programs, procedures or modules, and thus various subsets of these modules are, optionally, combined or otherwise re-arranged in various embodiments. In some embodiments, memory  102  optionally stores a subset of the modules and data structures identified above. Furthermore, memory  102  optionally stores additional modules and data structures not described above. 
     In some embodiments, device  100  is a device where operation of a predefined set of functions on the device is performed exclusively through a touch screen and/or a touchpad. By using a touch screen and/or a touchpad as the primary input control device for operation of device  100 , the number of physical input control devices (such as push buttons, dials, and the like) on device  100  is, optionally, reduced. 
     The predefined set of functions that are performed exclusively through a touch screen and/or a touchpad optionally include navigation between user interfaces. In some embodiments, the touchpad, when touched by the user, navigates device  100  to a main, home, or root menu from any user interface that is displayed on device  100 . In such embodiments, a “menu button” is implemented using a touchpad. In some other embodiments, the menu button is a physical push button or other physical input control device instead of a touchpad. 
       FIG. 1B  is a block diagram illustrating exemplary components for event handling in accordance with some embodiments. In some embodiments, memory  102  (in  FIGS. 1A ) or  370  ( FIG. 3 ) includes event sorter  170  (e.g., in operating system  126 ) and a respective application  136 - 1  (e.g., any of the aforementioned applications  136 ,  137 - 155 ,  380 - 390 ). 
     Event sorter  170  receives event information and determines the application  136 - 1  and application view  191  of application  136 - 1  to which to deliver the event information. Event sorter  170  includes event monitor  171  and event dispatcher module  174 . In some embodiments, application  136 - 1  includes application internal state  192 , which indicates the current application view(s) displayed on touch-sensitive display system  112  when the application is active or executing. In some embodiments, device/global internal state  157  is used by event sorter  170  to determine which application(s) is (are) currently active, and application internal state  192  is used by event sorter  170  to determine application views  191  to which to deliver event information. 
     In some embodiments, application internal state  192  includes additional information, such as one or more of: resume information to be used when application  136 - 1  resumes execution, user interface state information that indicates information being displayed or that is ready for display by application  136 - 1 , a state queue for enabling the user to go back to a prior state or view of application  136 - 1 , and a redo/undo queue of previous actions taken by the user. 
     Event monitor  171  receives event information from peripherals interface  118 . Event information includes information about a sub-event (e.g., a user touch on touch-sensitive display system  112 , as part of a multi-touch gesture). Peripherals interface  118  transmits information it receives from I/O subsystem  106  or a sensor, such as proximity sensor  166 , accelerometer(s)  168 , and/or microphone  113  (through audio circuitry  110 ). Information that peripherals interface  118  receives from I/O subsystem  106  includes information from touch-sensitive display system  112  or a touch-sensitive surface. 
     In some embodiments, event monitor  171  sends requests to the peripherals interface  118  at predetermined intervals. In response, peripherals interface  118  transmits event information. In other embodiments, peripheral interface  118  transmits event information only when there is a significant event (e.g., receiving an input above a predetermined noise threshold and/or for more than a predetermined duration). 
     In some embodiments, event sorter  170  also includes a hit view determination module  172  and/or an active event recognizer determination module  173 . 
     Hit view determination module  172  provides software procedures for determining where a sub-event has taken place within one or more views, when touch-sensitive display system  112  displays more than one view. Views are made up of controls and other elements that a user can see on the display. 
     Another aspect of the user interface associated with an application is a set of views, sometimes herein called application views or user interface windows, in which information is displayed and touch-based gestures occur. The application views (of a respective application) in which a touch is detected optionally correspond to programmatic levels within a programmatic or view hierarchy of the application. For example, the lowest level view in which a touch is detected is, optionally, called the hit view, and the set of events that are recognized as proper inputs are, optionally, determined based, at least in part, on the hit view of the initial touch that begins a touch-based gesture. 
     Hit view determination module  172  receives information related to sub-events of a touch-based gesture. When an application has multiple views organized in a hierarchy, hit view determination module  172  identifies a hit view as the lowest view in the hierarchy which should handle the sub-event. In most circumstances, the hit view is the lowest level view in which an initiating sub-event occurs (i.e., the first sub-event in the sequence of sub-events that form an event or potential event). Once the hit view is identified by the hit view determination module, the hit view typically receives all sub-events related to the same touch or input source for which it was identified as the hit view. 
     Active event recognizer determination module  173  determines which view or views within a view hierarchy should receive a particular sequence of sub-events. In some embodiments, active event recognizer determination module  173  determines that only the hit view should receive a particular sequence of sub-events. In other embodiments, active event recognizer determination module  173  determines that all views that include the physical location of a sub-event are actively involved views, and therefore determines that all actively involved views should receive a particular sequence of sub-events. In other embodiments, even if touch sub-events were entirely confined to the area associated with one particular view, views higher in the hierarchy would still remain as actively involved views. 
     Event dispatcher module  174  dispatches the event information to an event recognizer (e.g., event recognizer  180 ). In embodiments including active event recognizer determination module  173 , event dispatcher module  174  delivers the event information to an event recognizer determined by active event recognizer determination module  173 . In some embodiments, event dispatcher module  174  stores in an event queue the event information, which is retrieved by a respective event receiver module  182 . 
     In some embodiments, operating system  126  includes event sorter  170 . Alternatively, application  136 - 1  includes event sorter  170 . In yet other embodiments, event sorter  170  is a stand-alone module, or a part of another module stored in memory  102 , such as contact/motion module  130 . 
     In some embodiments, application  136 - 1  includes a plurality of event handlers  190  and one or more application views  191 , each of which includes instructions for handling touch events that occur within a respective view of the application&#39;s user interface. Each application view  191  of the application  136 - 1  includes one or more event recognizers  180 . Typically, a respective application view  191  includes a plurality of event recognizers  180 . In other embodiments, one or more of event recognizers  180  are part of a separate module, such as a user interface kit (not shown) or a higher level object from which application  136 - 1  inherits methods and other properties. In some embodiments, a respective event handler  190  includes one or more of: data updater  176 , object updater  177 , GUI updater  178 , and/or event data  179  received from event sorter  170 . Event handler  190  optionally utilizes or calls data updater  176 , object updater  177  or GUI updater  178  to update the application internal state  192 . Alternatively, one or more of the application views  191  includes one or more respective event handlers  190 . Also, in some embodiments, one or more of data updater  176 , object updater  177 , and GUI updater  178  are included in a respective application view  191 . 
     A respective event recognizer  180  receives event information (e.g., event data  179 ) from event sorter  170 , and identifies an event from the event information. Event recognizer  180  includes event receiver  182  and event comparator  184 . In some embodiments, event recognizer  180  also includes at least a subset of: metadata  183 , and event delivery instructions  188  (which optionally include sub-event delivery instructions). 
     Event receiver  182  receives event information from event sorter  170 . The event information includes information about a sub-event, for example, a touch or a touch movement. Depending on the sub-event, the event information also includes additional information, such as location of the sub-event. When the sub-event concerns motion of a touch, the event information optionally also includes speed and direction of the sub-event. In some embodiments, events include rotation of the device from one orientation to another (e.g., from a portrait orientation to a landscape orientation, or vice versa), and the event information includes corresponding information about the current orientation (also called device attitude) of the device. 
     Event comparator  184  compares the event information to predefined event or sub-event definitions and, based on the comparison, determines an event or sub-event, or determines or updates the state of an event or sub-event. In some embodiments, event comparator  184  includes event definitions  186 . Event definitions  186  contain definitions of events (e.g., predefined sequences of sub-events), for example, event  1  ( 187 - 1 ), event  2  ( 187 - 2 ), and others. In some embodiments, sub-events in an event  187  include, for example, touch begin, touch end, touch movement, touch cancellation, and multiple touching. In one example, the definition for event  1  ( 187 - 1 ) is a double tap on a displayed object. The double tap, for example, comprises a first touch (touch begin) on the displayed object for a predetermined phase, a first lift-off (touch end) for a predetermined phase, a second touch (touch begin) on the displayed object for a predetermined phase, and a second lift-off (touch end) for a predetermined phase. In another example, the definition for event  2  ( 187 - 2 ) is a dragging on a displayed object. The dragging, for example, comprises a touch (or contact) on the displayed object for a predetermined phase, a movement of the touch across touch-sensitive display system  112 , and lift-off of the touch (touch end). In some embodiments, the event also includes information for one or more associated event handlers  190 . 
     In some embodiments, event definition  187  includes a definition of an event for a respective user-interface object. In some embodiments, event comparator  184  performs a hit test to determine which user-interface object is associated with a sub-event. For example, in an application view in which three user-interface objects are displayed on touch-sensitive display system  112 , when a touch is detected on touch-sensitive display system  112 , event comparator  184  performs a hit test to determine which of the three user-interface objects is associated with the touch (sub-event). If each displayed object is associated with a respective event handler  190 , the event comparator uses the result of the hit test to determine which event handler  190  should be activated. For example, event comparator  184  selects an event handler associated with the sub-event and the object triggering the hit test. 
     In some embodiments, the definition for a respective event  187  also includes delayed actions that delay delivery of the event information until after it has been determined whether the sequence of sub-events does or does not correspond to the event recognizer&#39;s event type. 
     When a respective event recognizer  180  determines that the series of sub-events do not match any of the events in event definitions  186 , the respective event recognizer  180  enters an event impossible, event failed, or event ended state, after which it disregards subsequent sub-events of the touch-based gesture. In this situation, other event recognizers, if any, that remain active for the hit view continue to track and process sub-events of an ongoing touch-based gesture. 
     In some embodiments, a respective event recognizer  180  includes metadata  183  with configurable properties, flags, and/or lists that indicate how the event delivery system should perform sub-event delivery to actively involved event recognizers. In some embodiments, metadata  183  includes configurable properties, flags, and/or lists that indicate how event recognizers interact, or are enabled to interact, with one another. In some embodiments, metadata  183  includes configurable properties, flags, and/or lists that indicate whether sub-events are delivered to varying levels in the view or programmatic hierarchy. 
     In some embodiments, a respective event recognizer  180  activates event handler  190  associated with an event when one or more particular sub-events of an event are recognized. In some embodiments, a respective event recognizer  180  delivers event information associated with the event to event handler  190 . Activating an event handler  190  is distinct from sending (and deferred sending) sub-events to a respective hit view. In some embodiments, event recognizer  180  throws a flag associated with the recognized event, and event handler  190  associated with the flag catches the flag and performs a predefined process. 
     In some embodiments, event delivery instructions  188  include sub-event delivery instructions that deliver event information about a sub-event without activating an event handler. Instead, the sub-event delivery instructions deliver event information to event handlers associated with the series of sub-events or to actively involved views. Event handlers associated with the series of sub-events or with actively involved views receive the event information and perform a predetermined process. 
     In some embodiments, data updater  176  creates and updates data used in application  136 - 1 . For example, data updater  176  updates the telephone number used in contacts module  137 , or stores a video file used in video player module  145 . In some embodiments, object updater  177  creates and updates objects used in application  136 - 1 . For example, object updater  177  creates a new user-interface object or updates the position of a user-interface object. GUI updater  178  updates the GUI. For example, GUI updater  178  prepares display information and sends it to graphics module  132  for display on a touch-sensitive display. 
     In some embodiments, event handler(s)  190  includes or has access to data updater  176 , object updater  177 , and GUI updater  178 . In some embodiments, data updater  176 , object updater  177 , and GUI updater  178  are included in a single module of a respective application  136 - 1  or application view  191 . In other embodiments, they are included in two or more software modules. 
     It shall be understood that the foregoing discussion regarding event handling of user touches on touch-sensitive displays also applies to other forms of user inputs to operate multifunction devices  100  with input-devices, not all of which are initiated on touch screens. For example, mouse movement and mouse button presses, optionally coordinated with single or multiple keyboard presses or holds; contact movements such as taps, drags, scrolls, etc., on touch-pads; pen stylus inputs; movement of the device; oral instructions; detected eye movements; biometric inputs; and/or any combination thereof are optionally utilized as inputs corresponding to sub-events which define an event to be recognized. 
       FIG. 2  illustrates a portable multifunction device  100  having a touch screen (e.g., touch-sensitive display system  112 ,  FIG. 1A ) in accordance with some embodiments. The touch screen optionally displays one or more graphics within user interface (UI)  200 . In this embodiment, as well as others described below, a user is enabled to select one or more of the graphics by making a gesture on the graphics, for example, with one or more fingers  202  (not drawn to scale in the figure) or one or more styluses  203  (not drawn to scale in the figure). In some embodiments, selection of one or more graphics occurs when the user breaks contact with the one or more graphics. In some embodiments, the gesture optionally includes one or more taps, one or more swipes (from left to right, right to left, upward and/or downward) and/or a rolling of a finger (from right to left, left to right, upward and/or downward) that has made contact with device  100 . In some implementations or circumstances, inadvertent contact with a graphic does not select the graphic. For example, a swipe gesture that sweeps over an application icon optionally does not select the corresponding application when the gesture corresponding to selection is a tap. 
     Device  100  optionally also includes one or more physical buttons, such as “home” or menu button  204 . As described previously, menu button  204  is, optionally, used to navigate to any application  136  in a set of applications that are, optionally executed on device  100 . Alternatively, in some embodiments, the menu button is implemented as a soft key in a GUI displayed on the touch-screen display. 
     In some embodiments, device  100  includes the touch-screen display, menu button  204 , push button  206  for powering the device on/off and locking the device, volume adjustment button(s)  208 , Subscriber Identity Module (SIM) card slot  210 , head set jack  212 , and docking/charging external port  124 . Push button  206  is, optionally, used to turn the power on/off on the device by depressing the button and holding the button in the depressed state for a predefined time interval; to lock the device by depressing the button and releasing the button before the predefined time interval has elapsed; and/or to unlock the device or initiate an unlock process. In some embodiments, device  100  also accepts verbal input for activation or deactivation of some functions through microphone  113 . Device  100  also, optionally, includes one or more contact intensity sensors  165  for detecting intensity of contacts on touch-sensitive display system  112  and/or one or more tactile output generators  167  for generating tactile outputs for a user of device  100 . 
       FIG. 3  is a block diagram of an exemplary multifunction device with a display and a touch-sensitive surface in accordance with some embodiments. Device  300  need not be portable. In some embodiments, device  300  is a laptop computer, a desktop computer, a tablet computer, a multimedia player device, a navigation device, an educational device (such as a child&#39;s learning toy), a gaming system, or a control device (e.g., a home or industrial controller). Device  300  typically includes one or more processing units (CPU&#39;s)  310 , one or more network or other communications interfaces  360 , memory  370 , and one or more communication buses  320  for interconnecting these components. Communication buses  320  optionally include circuitry (sometimes called a chipset) that interconnects and controls communications between system components. Device  300  includes input/output (I/O) interface  330  comprising display  340 , which is typically a touch-screen display. I/O interface  330  also optionally includes a keyboard and/or mouse (or other pointing device)  350  and touchpad  355 , tactile output generator  357  for generating tactile outputs on device  300  (e.g., similar to tactile output generator(s)  167  described above with reference to  FIG. 1A ), sensors  359  (e.g., optical, acceleration, proximity, touch-sensitive, and/or contact intensity sensors similar to contact intensity sensor(s)  165  described above with reference to  FIG. 1A ). Memory  370  includes high-speed random access memory, such as DRAM, SRAM, DDR RAM or other random access solid state memory devices; and optionally includes non-volatile memory, such as one or more magnetic disk storage devices, optical disk storage devices, flash memory devices, or other non-volatile solid state storage devices. Memory  370  optionally includes one or more storage devices remotely located from CPU(s)  310 . In some embodiments, memory  370  stores programs, modules, and data structures analogous to the programs, modules, and data structures stored in memory  102  of portable multifunction device  100  ( FIG. 1A ), or a subset thereof. Furthermore, memory  370  optionally stores additional programs, modules, and data structures not present in memory  102  of portable multifunction device  100 . For example, memory  370  of device  300  optionally stores drawing module  380 , presentation module  382 , word processing module  384 , web site creation module  386 , disk authoring module  388 , and/or spreadsheet module  390 , while memory  102  of portable multifunction device  100  ( FIG. 1A ) optionally does not store these modules. 
     Each of the above identified elements in  FIG. 3  are, optionally, stored in one or more of the previously mentioned memory devices. Each of the above identified modules corresponds to a set of instructions for performing a function described above. The above identified modules or programs (i.e., sets of instructions) need not be implemented as separate software programs, procedures or modules, and thus various subsets of these modules are, optionally, combined or otherwise re-arranged in various embodiments. In some embodiments, memory  370  optionally stores a subset of the modules and data structures identified above. Furthermore, memory  370  optionally stores additional modules and data structures not described above. 
     Attention is now directed towards embodiments of user interfaces (“UI”) that are, optionally, implemented on portable multifunction device  100 . 
       FIG. 4A  illustrates an exemplary user interface for a menu of applications on portable multifunction device  100  in accordance with some embodiments. Similar user interfaces are, optionally, implemented on device  300 . In some embodiments, user interface  400  includes the following elements, or a subset or superset thereof:
         Signal strength indicator(s)  402  for wireless communication(s), such as cellular and Wi-Fi signals;   Time  404 ;   Bluetooth indicator  405 ;   Battery status indicator  406 ;   Tray  408  with icons for frequently used applications, such as:
           Icon  416  for telephone module  138 , labeled “Phone,” which optionally includes an indicator  414  of the number of missed calls or voicemail messages;   Icon  418  for e-mail client module  140 , labeled “Mail,” which optionally includes an indicator  410  of the number of unread e-mails;   Icon  420  for browser module  147 , labeled “Browser;” and   Icon  422  for video and music player module  152 , also referred to as iPod (trademark of Apple Inc.) module  152 , labeled “iPod;” and   
           Icons for other applications, such as:
           Icon  424  for IM module  141 , labeled “Messages;”   Icon  426  for calendar module  148 , labeled “Calendar;”   Icon  428  for image management module  144 , labeled “Photos;”   Icon  430  for camera module  143 , labeled “Camera;”   Icon  432  for online video module  155 , labeled “Online Video;”   Icon  434  for stocks widget  149 - 2 , labeled “Stocks;”   Icon  436  for map module  154 , labeled “Map;”   Icon  438  for weather widget  149 - 1 , labeled “Weather;”   Icon  440  for alarm clock widget  149 - 4 , labeled “Clock;”   Icon  442  for workout support module  142 , labeled “Workout Support;”   Icon  444  for notes module  153 , labeled “Notes;” and   Icon  446  for a settings application or module, which provides access to settings for device  100  and its various applications  136 .   
               

     It should be noted that the icon labels illustrated in  FIG. 4A  are merely exemplary. For example, in some embodiments, icon  422  for video and music player module  152  is labeled “Music” or “Music Player.” Other labels are, optionally, used for various application icons. In some embodiments, a label for a respective application icon includes a name of an application corresponding to the respective application icon. In some embodiments, a label for a particular application icon is distinct from a name of an application corresponding to the particular application icon. 
       FIG. 4B  illustrates an exemplary user interface on a device (e.g., device  300 ,  FIG. 3 ) with a touch-sensitive surface  451  (e.g., a tablet or touchpad  355 ,  FIG. 3 ) that is separate from the display  450 . Device  300  also, optionally, includes one or more contact intensity sensors (e.g., one or more of sensors  357 ) for detecting intensity of contacts on touch-sensitive surface  451  and/or one or more tactile output generators  359  for generating tactile outputs for a user of device  300 . 
       FIG. 4B  illustrates an exemplary user interface on a device (e.g., device  300 ,  FIG. 3 ) with a touch-sensitive surface  451  (e.g., a tablet or touchpad  355 ,  FIG. 3 ) that is separate from the display  450 . Although many of the examples that follow will be given with reference to inputs on touch screen display  112  (where the touch-sensitive surface and the display are combined), in some embodiments, the device detects inputs on a touch-sensitive surface that is separate from the display, as shown in  FIG. 4B . In some embodiments, the touch-sensitive surface (e.g.,  451  in  FIG. 4B ) has a primary axis (e.g.,  452  in  FIG. 4B ) that corresponds to a primary axis (e.g.,  453  in  FIG. 4B ) on the display (e.g.,  450 ). In accordance with these embodiments, the device detects contacts (e.g.,  460  and  462  in  FIG. 4B ) with the touch-sensitive surface  451  at locations that correspond to respective locations on the display (e.g., in  FIG. 4B, 460  corresponds to  468  and  462  corresponds to  470 ). In this way, user inputs (e.g., contacts  460  and  462 , and movements thereof) detected by the device on the touch-sensitive surface (e.g.,  451  in  FIG. 4B ) are used by the device to manipulate the user interface on the display (e.g.,  450  in  FIG. 4B ) of the multifunction device when the touch-sensitive surface is separate from the display. It should be understood that similar methods are, optionally, used for other user interfaces described herein. 
     Additionally, while the following examples are given primarily with reference to finger inputs (e.g., finger contacts, finger tap gestures, finger swipe gestures, etc.), it should be understood that, in some embodiments, one or more of the finger inputs are replaced with input from another input device (e.g., a mouse based input or a stylus input). For example, a swipe gesture is, optionally, replaced with a mouse click (e.g., instead of a contact) followed by movement of the cursor along the path of the swipe (e.g., instead of movement of the contact). As another example, a tap gesture is, optionally, replaced with a mouse click while the cursor is located over the location of the tap gesture (e.g., instead of detection of the contact followed by ceasing to detect the contact). Similarly, when multiple user inputs are simultaneously detected, it should be understood that multiple computer mice are, optionally, used simultaneously, or a mouse and finger contacts are, optionally, used simultaneously. 
     As used herein, the term “focus selector” refers to an input element that indicates a current part of a user interface with which a user is interacting. In some implementations that include a cursor or other location marker, the cursor acts as a “focus selector,” so that when an input (e.g., a press input) is detected on a touch-sensitive surface (e.g., touchpad  355  in  FIG. 3  or touch-sensitive surface  451  in  FIG. 4B ) while the cursor is over a particular user interface element (e.g., a button, window, slider or other user interface element), the particular user interface element is adjusted in accordance with the detected input. In some implementations that include a touch-screen display (e.g., touch-sensitive display system  112  in  FIG. 1A  or the touch screen in  FIG. 4A ) that enables direct interaction with user interface elements on the touch-screen display, a detected contact on the touch-screen acts as a “focus selector,” so that when an input (e.g., a press input by the contact) is detected on the touch-screen display at a location of a particular user interface element (e.g., a button, window, slider or other user interface element), the particular user interface element is adjusted in accordance with the detected input. In some implementations, focus is moved from one region of a user interface to another region of the user interface without corresponding movement of a cursor or movement of a contact on a touch-screen display (e.g., by using a tab key or arrow keys to move focus from one button to another button); in these implementations, the focus selector moves in accordance with movement of focus between different regions of the user interface. Without regard to the specific form taken by the focus selector, the focus selector is generally the user interface element (or contact on a touch-screen display) that is controlled by the user so as to communicate the user&#39;s intended interaction with the user interface (e.g., by indicating, to the device, the element of the user interface with which the user is intending to interact). For example, the location of a focus selector (e.g., a cursor, a contact, or a selection box) over a respective button while a press input is detected on the touch-sensitive surface (e.g., a touchpad or touch screen) will indicate that the user is intending to activate the respective button (as opposed to other user interface elements shown on a display of the device). 
     As used in the specification and claims, the term “intensity” of a contact on a touch-sensitive surface refers to the force or pressure (force per unit area) of a contact (e.g., a finger contact or a stylus contact) on the touch-sensitive surface, or to a substitute (proxy) for the force or pressure of a contact on the touch-sensitive surface. The intensity of a contact has a range of values that includes at least four distinct values and more typically includes hundreds of distinct values (e.g., at least 256). Intensity of a contact is, optionally, determined (or measured) using various approaches and various sensors or combinations of sensors. For example, one or more force sensors underneath or adjacent to the touch-sensitive surface are, optionally, used to measure force at various points on the touch-sensitive surface. In some implementations, force measurements from multiple force sensors are combined (e.g., a weighted average or a sum) to determine an estimated force of a contact. Similarly, a pressure-sensitive tip of a stylus is, optionally, used to determine a pressure of the stylus on the touch-sensitive surface. Alternatively, the size of the contact area detected on the touch-sensitive surface and/or changes thereto, the capacitance of the touch-sensitive surface proximate to the contact and/or changes thereto, and/or the resistance of the touch-sensitive surface proximate to the contact and/or changes thereto are, optionally, used as a substitute for the force or pressure of the contact on the touch-sensitive surface. In some implementations, the substitute measurements for contact force or pressure are used directly to determine whether an intensity threshold has been exceeded (e.g., the intensity threshold is described in units corresponding to the substitute measurements). In some implementations, the substitute measurements for contact force or pressure are converted to an estimated force or pressure and the estimated force or pressure is used to determine whether an intensity threshold has been exceeded (e.g., the intensity threshold is a pressure threshold measured in units of pressure). Using the intensity of a contact as an attribute of a user input allows for user access to additional device functionality that may otherwise not be readily accessible by the user on a reduced-size device with limited real estate for displaying affordances (e.g., on a touch-sensitive display) and/or receiving user input (e.g., via a touch-sensitive display, a touch-sensitive surface, or a physical/mechanical control such as a knob or a button). 
     In some embodiments, contact/motion module  130  uses a set of one or more intensity thresholds to determine whether an operation has been performed by a user (e.g., to determine whether a user has “clicked” on an icon). In some embodiments, at least a subset of the intensity thresholds are determined in accordance with software parameters (e.g., the intensity thresholds are not determined by the activation thresholds of particular physical actuators and can be adjusted without changing the physical hardware of device  100 ). For example, a mouse “click” threshold of a trackpad or touch-screen display can be set to any of a large range of predefined thresholds values without changing the trackpad or touch-screen display hardware. Additionally, in some implementations a user of the device is provided with software settings for adjusting one or more of the set of intensity thresholds (e.g., by adjusting individual intensity thresholds and/or by adjusting a plurality of intensity thresholds at once with a system-level click “intensity” parameter). 
     As used in the specification and claims, the term “characteristic intensity” of a contact refers to a characteristic of the contact based on one or more intensities of the contact. In some embodiments, the characteristic intensity is based on multiple intensity samples. The characteristic intensity is, optionally, based on a predefined number of intensity samples, or a set of intensity samples collected during a predetermined time period (e.g., 0.05, 0.1, 0.2, 0.5, 1, 2, 5, 10 seconds) relative to a predefined event (e.g., after detecting the contact, prior to detecting liftoff of the contact, before or after detecting a start of movement of the contact, prior to detecting an end of the contact, before or after detecting an increase in intensity of the contact, and/or before or after detecting a decrease in intensity of the contact). A characteristic intensity of a contact is, optionally based on one or more of: a maximum value of the intensities of the contact, a mean value of the intensities of the contact, an average value of the intensities of the contact, a top 10 percentile value of the intensities of the contact, a value at the half maximum of the intensities of the contact, a value at the 90 percent maximum of the intensities of the contact, or the like. In some embodiments, the duration of the contact is used in determining the characteristic intensity (e.g., when the characteristic intensity is an average of the intensity of the contact over time). In some embodiments, the characteristic intensity is compared to a set of one or more intensity thresholds to determine whether an operation has been performed by a user. For example, the set of one or more intensity thresholds may include a first intensity threshold and a second intensity threshold. In this example, a contact with a characteristic intensity that does not exceed the first threshold results in a first operation, a contact with a characteristic intensity that exceeds the first intensity threshold and does not exceed the second intensity threshold results in a second operation, and a contact with a characteristic intensity that exceeds the second intensity threshold results in a third operation. In some embodiments, a comparison between the characteristic intensity and one or more intensity thresholds is used to determine whether or not to perform one or more operations (e.g., whether to perform a respective option or forgo performing the respective operation) rather than being used to determine whether to perform a first operation or a second operation. 
     In some embodiments, a portion of a gesture is identified for purposes of determining a characteristic intensity. For example, a touch-sensitive surface may receive a continuous swipe contact transitioning from a start location and reaching an end location (e.g., a drag gesture), at which point the intensity of the contact increases. In this example, the characteristic intensity of the contact at the end location may be based on only a portion of the continuous swipe contact, and not the entire swipe contact (e.g., only the portion of the swipe contact at the end location). In some embodiments, a smoothing algorithm may be applied to the intensities of the swipe contact prior to determining the characteristic intensity of the contact. For example, the smoothing algorithm optionally includes one or more of: an unweighted sliding-average smoothing algorithm, a triangular smoothing algorithm, a median filter smoothing algorithm, and/or an exponential smoothing algorithm. In some circumstances, these smoothing algorithms eliminate narrow spikes or dips in the intensities of the swipe contact for purposes of determining a characteristic intensity. 
     The user interface figures described herein (e.g.,  FIGS. 5A-5HH, 6A-6V, 7A-7O, 8A-8R, 9A-9H, 22A-23BA ) optionally include various intensity diagrams that show the current intensity of the contact on the touch-sensitive surface relative to one or more intensity thresholds (e.g., a contact detection intensity threshold IT 0 , a hint intensity threshold IT H , a light press intensity threshold IT L , a deep press intensity threshold IT D  (e.g., that is at least initially higher than I L ), and/or one or more other intensity thresholds (e.g., an intensity threshold I H  that is lower than I L )). This intensity diagram is typically not part of the displayed user interface, but is provided to aid in the interpretation of the figures. In some embodiments, the light press intensity threshold corresponds to an intensity at which the device will perform operations typically associated with clicking a button of a physical mouse or a trackpad. In some embodiments, the deep press intensity threshold corresponds to an intensity at which the device will perform operations that are different from operations typically associated with clicking a button of a physical mouse or a trackpad. In some embodiments, when a contact is detected with a characteristic intensity below the light press intensity threshold (e.g., and above a nominal contact-detection intensity threshold IT 0  below which the contact is no longer detected), the device will move a focus selector in accordance with movement of the contact on the touch-sensitive surface without performing an operation associated with the light press intensity threshold or the deep press intensity threshold. Generally, unless otherwise stated, these intensity thresholds are consistent between different sets of user interface figures. 
     In some embodiments, the response of the device to inputs detected by the device depends on criteria based on the contact intensity during the input. For example, for some “light press” inputs, the intensity of a contact exceeding a first intensity threshold during the input triggers a first response. In some embodiments, the response of the device to inputs detected by the device depends on criteria that include both the contact intensity during the input and time-based criteria. For example, for some “deep press” inputs, the intensity of a contact exceeding a second intensity threshold during the input, greater than the first intensity threshold for a light press, triggers a second response only if a delay time has elapsed between meeting the first intensity threshold and meeting the second intensity threshold. This delay time is typically less than 200 ms in duration (e.g., 40, 100, or 120 ms, depending on the magnitude of the second intensity threshold, with the delay time increasing as the second intensity threshold increases). This delay time helps to avoid accidental deep press inputs. As another example, for some “deep press” inputs, there is a reduced-sensitivity time period that occurs after the time at which the first intensity threshold is met. During the reduced-sensitivity time period, the second intensity threshold is increased. This temporary increase in the second intensity threshold also helps to avoid accidental deep press inputs. For other deep press inputs, the response to detection of a deep press input does not depend on time-based criteria. 
     In some embodiments, one or more of the input intensity thresholds and/or the corresponding outputs vary based on one or more factors, such as user settings, contact motion, input timing, application running, rate at which the intensity is applied, number of concurrent inputs, user history, environmental factors (e.g., ambient noise), focus selector position, and the like. Exemplary factors are described in U.S. patent application Ser. Nos. 14/399,606 and 14/624,296, which are incorporated by reference herein in their entireties. 
     For example,  FIG. 4C  illustrates a dynamic intensity threshold  480  that changes over time based in part on the intensity of touch input  476  over time. Dynamic intensity threshold  480  is a sum of two components, first component  474  that decays over time after a predefined delay time p 1  from when touch input  476  is initially detected, and second component  478  that trails the intensity of touch input  476  over time. The initial high intensity threshold of first component  474  reduces accidental triggering of a “deep press” response, while still allowing an immediate “deep press” response if touch input  476  provides sufficient intensity. Second component  478  reduces unintentional triggering of a “deep press” response by gradual intensity fluctuations of in a touch input. In some embodiments, when touch input  476  satisfies dynamic intensity threshold  480  (e.g., at point  481  in  FIG. 4C ), the “deep press” response is triggered. 
       FIG. 4D  illustrates another dynamic intensity threshold  486  (e.g., intensity threshold I D ).  FIG. 4D  also illustrates two other intensity thresholds: a first intensity threshold I H  and a second intensity threshold I L . In  FIG. 4D , although touch input  484  satisfies the first intensity threshold I H  and the second intensity threshold I L  prior to time p 2 , no response is provided until delay time p 2  has elapsed at time  482 . Also in  FIG. 4D , dynamic intensity threshold  486  decays over time, with the decay starting at time  488  after a predefined delay time p 1  has elapsed from time  482  (when the response associated with the second intensity threshold I L  was triggered). This type of dynamic intensity threshold reduces accidental triggering of a response associated with the dynamic intensity threshold I D  immediately after, or concurrently with, triggering a response associated with a lower intensity threshold, such as the first intensity threshold I H  or the second intensity threshold I L . 
       FIG. 4E  illustrate yet another dynamic intensity threshold  492  (e.g., intensity threshold I D ). In  FIG. 4E , a response associated with the intensity threshold I L  is triggered after the delay time p 2  has elapsed from when touch input  490  is initially detected. Concurrently, dynamic intensity threshold  492  decays after the predefined delay time p 1  has elapsed from when touch input  490  is initially detected. So a decrease in intensity of touch input  490  after triggering the response associated with the intensity threshold I L , followed by an increase in the intensity of touch input  490 , without releasing touch input  490 , can trigger a response associated with the intensity threshold I D  (e.g., at time  494 ) even when the intensity of touch input  490  is below another intensity threshold, for example, the intensity threshold I L . 
     An increase of characteristic intensity of the contact from an intensity below the light press intensity threshold IT L  to an intensity between the light press intensity threshold IT L  and the deep press intensity threshold IT D  is sometimes referred to as a “light press” input. An increase of characteristic intensity of the contact from an intensity below the deep press intensity threshold IT D  to an intensity above the deep press intensity threshold IT D  is sometimes referred to as a “deep press” input. An increase of characteristic intensity of the contact from an intensity below the contact-detection intensity threshold IT 0  to an intensity between the contact-detection intensity threshold IT 0  and the light press intensity threshold IT L  is sometimes referred to as detecting the contact on the touch-surface. A decrease of characteristic intensity of the contact from an intensity above the contact-detection intensity threshold IT 0  to an intensity below the contact-detection intensity threshold IT 0  is sometimes referred to as detecting liftoff of the contact from the touch-surface. In some embodiments IT 0  is zero. In some embodiments, IT 0  is greater than zero. In some illustrations a shaded circle or oval is used to represent intensity of a contact on the touch-sensitive surface. In some illustrations, a circle or oval without shading is used represent a respective contact on the touch-sensitive surface without specifying the intensity of the respective contact. 
     In some embodiments, described herein, one or more operations are performed in response to detecting a gesture that includes a respective press input or in response to detecting the respective press input performed with a respective contact (or a plurality of contacts), where the respective press input is detected based at least in part on detecting an increase in intensity of the contact (or plurality of contacts) above a press-input intensity threshold. In some embodiments, the respective operation is performed in response to detecting the increase in intensity of the respective contact above the press-input intensity threshold (e.g., the respective operation is performed on a “down stroke” of the respective press input). In some embodiments, the press input includes an increase in intensity of the respective contact above the press-input intensity threshold and a subsequent decrease in intensity of the contact below the press-input intensity threshold, and the respective operation is performed in response to detecting the subsequent decrease in intensity of the respective contact below the press-input threshold (e.g., the respective operation is performed on an “up stroke” of the respective press input). 
     In some embodiments, the device employs intensity hysteresis to avoid accidental inputs sometimes termed “jitter,” where the device defines or selects a hysteresis intensity threshold with a predefined relationship to the press-input intensity threshold (e.g., the hysteresis intensity threshold is X intensity units lower than the press-input intensity threshold or the hysteresis intensity threshold is 75%, 90%, or some reasonable proportion of the press-input intensity threshold). Thus, in some embodiments, the press input includes an increase in intensity of the respective contact above the press-input intensity threshold and a subsequent decrease in intensity of the contact below the hysteresis intensity threshold that corresponds to the press-input intensity threshold, and the respective operation is performed in response to detecting the subsequent decrease in intensity of the respective contact below the hysteresis intensity threshold (e.g., the respective operation is performed on an “up stroke” of the respective press input). Similarly, in some embodiments, the press input is detected only when the device detects an increase in intensity of the contact from an intensity at or below the hysteresis intensity threshold to an intensity at or above the press-input intensity threshold and, optionally, a subsequent decrease in intensity of the contact to an intensity at or below the hysteresis intensity, and the respective operation is performed in response to detecting the press input (e.g., the increase in intensity of the contact or the decrease in intensity of the contact, depending on the circumstances). 
     For ease of explanation, the description of operations performed in response to a press input associated with a press-input intensity threshold or in response to a gesture including the press input are, optionally, triggered in response to detecting: an increase in intensity of a contact above the press-input intensity threshold, an increase in intensity of a contact from an intensity below the hysteresis intensity threshold to an intensity above the press-input intensity threshold, a decrease in intensity of the contact below the press-input intensity threshold, or a decrease in intensity of the contact below the hysteresis intensity threshold corresponding to the press-input intensity threshold. Additionally, in examples where an operation is described as being performed in response to detecting a decrease in intensity of a contact below the press-input intensity threshold, the operation is, optionally, performed in response to detecting a decrease in intensity of the contact below a hysteresis intensity threshold corresponding to, and lower than, the press-input intensity threshold. As described above, in some embodiments, the triggering of these responses also depends on time-based criteria being met (e.g., a delay time has elapsed between a first intensity threshold being met and a second intensity threshold being met). 
     User Interfaces and Associated Processes 
     Attention is now directed towards embodiments of user interfaces (“UI”) and associated processes that may be implemented on an electronic device, such as portable multifunction device  100  or device  300 , with a display, a touch-sensitive surface, and one or more sensors to detect intensities of contacts with the touch-sensitive surface. 
       FIGS. 5A-5HH  illustrate exemplary user interfaces for navigating between user interfaces in accordance with some embodiments. The user interfaces in these figures are used to illustrate the processes described below, including the processes in  FIGS. 10A-10H, 11A-11E, 12A-12E, 13A-13D, 14A-14C, 15, 24A-24F, and 25A-25H . For convenience of explanation, some of the embodiments will be discussed with reference to operations performed on a device with a touch-sensitive display system  112 . In such embodiments, the focus selector is, optionally: a respective finger or stylus contact, a representative point corresponding to a finger or stylus contact (e.g., a centroid of a respective contact or a point associated with a respective contact), or a centroid of two or more contacts detected on the touch-sensitive display system  112 . However, analogous operations are, optionally, performed on a device with a display  450  and a separate touch-sensitive surface  451  in response to detecting the contacts on the touch-sensitive surface  451  while displaying the user interfaces shown in the figures on the display  450 , along with a focus selector. 
       FIGS. 5A-5T  illustrate exemplary embodiments of a user interface selection mode that allows a user to efficiently navigate between multiple user interfaces on an electronic device (e.g., multifunction device  100 ) in accordance with some embodiments. Exemplary user interfaces (e.g., user interface  506  displayed on touch screen  112 ) for the user interface selection mode include representations of multiple user interfaces (e.g., representations  508 ,  510 ,  526 ,  534 ,  540 , and  552  of user interfaces  502 ,  507 ,  524 ,  536 ,  542 , and  552 , respectively for applications associated with the electronic device displayed as a virtual stack of cards (e.g., the “stack”). User inputs (e.g., contacts, swipe/drag gestures, flick gestures, etc.) detected on touch screen  112  (e.g., a touch-sensitive surface) are used to navigate between user interfaces that can be selected for display on the screen.  FIG. 5A  illustrates display of a graphical user interface  502  for a web browsing application on the electronic device. User interface  502  includes display of status bar  504  that provides information to the user (e.g., signal strength indicator(s)  402  for wireless communication(s), time  404 , bluetooth indicator  405 , and battery status indicator  406 ). As illustrated in  FIGS. 5B-5C , the device enters a user interface selection mode upon detecting deep press  504  on the left side of the bezel of the device (e.g., an exemplary predetermined input) that includes an increase in intensity of a contact from an intensity below IT D  to an intensity above IT D . 
     In some embodiments, a system level gesture is used to activate a user interface selection mode. For example, as illustrated in  FIGS. 5B  and SC, a deep press on the left side of the bezel of the device activates the user interface selection mode. In an alternative embodiment, as illustrated in  FIGS. 5EE and 5C , where the device is capable of distinguishing between user thumb contacts and user finger contacts, detection of deep thumb press  570  on touch-screen  112  (e.g., anywhere on an associated touch-sensitive surface) activates the user interface selection mode (e.g., device  100  replaces display of user interface  502  with display of user interface  506  in response to detecting a thumb press that includes an increase in intensity of a contact from an intensity below IT D  to an intensity above IT D ). In contrast, as illustrated in  FIGS. 5FF-5GG , in response to detecting deep finger press  572  within user interface  502  (e.g., at the same position that device  100  detected thumb deep press  570  in  FIG. 5EE ), the device previews web content associated with an object displayed at the location of deep finger press  572  (e.g., the device displays preview window  574  in  FIG. 5GG ). Thus, in some embodiments, the device distinguishes between both the type of gesture (e.g., deep thumb press vs. deep finger press) and the location of the gesture (e.g., deep finger press on the left side of the bezel vs. deep finger press within the user interface) when selecting between activating a user interface selection mode and performing an application-specific operation (e.g., previewing web content). 
       FIGS. 5C-5F  illustrate exemplary user interfaces (e.g., graphical user interface  502 ) for the user interface selection mode that include representation  508  of web browsing user interface  502  that was displayed on touch screen  112  immediately preceding entry into the user interface selection mode and at least representation  510  of messaging user interface  506 . 
     Optional title bars  512  and  522  provide information about the user interface being represented in the card. For example, title bar  512  includes the name “Safari”  514  and icon  516  associated with the web browsing application user interface  502  represented in card  508 . Similarly, title bar  522  includes the name “Messages”  520  and icon  518  associated with messaging application user interface  506  represented in card  510 . In some embodiments, the title area (e.g., title bar) is not part of the user interface representation card. In some embodiments, the title bar is not illustrated as detached from the user interface representation card. In some embodiments, title information (e.g., a title bar, application name, and/or icon corresponding to an application) is displayed as hovering above or below the user interface representation card. In some embodiments, the user interface selection mode does not include display of title information. 
       FIGS. 5C-5E  illustrate exemplary user interfaces for the user interface selection mode that display the user interface representations without substantial depth (e.g., in a substantially two-dimensional representation), as if the user is looking down at a deck of cards being spread out on a table. As illustrated, multiple cards are viewed as if spread out in a straight line to the right from the top of a stack of cards on the left hand side of the display. However, in some embodiments, the cards are spread out to the left from the top of a stack of cards on the right hand side of the display, and/or spread out askew or along a non-linear path (e.g., along a curved or seemingly random path). 
       FIG. 5C  illustrates an embodiment where the card for the user interface that was displayed immediately prior to entering the user interface selection mode is displayed as the top card in the user interface selection stack. For example, user interface  502  shows web browsing card  508  (e.g., representation  508  of web browsing user interface  502 ) displayed over messaging card  510  (e.g., representation  510  of messaging user interface  507 ). 
       FIG. 5D  illustrates an embodiment where the card for the user interface that was displayed immediately prior to entering the user interface selection mode is displayed further back in the user interface selection stack. For example, user interface  502  shows web browsing card  508  (e.g., representation  508  of web browsing user interface  502 ) displayed under messaging card  510  (e.g., representation  510  of messaging user interface  507 ). 
       FIG. 5E  illustrates an embodiment where the stack includes more than two cards. For example, user interface  502  shows web browsing card  508  displayed over messaging card  510 , which in turn is displayed over photo card  526  (e.g., representation  526  of user interface  524  for an image management application). The cards at the top of the stack are spread out more relative to each other than are the cards further back in the stack, revealing more of the cards at the top of the stack than those further back. For example, web browsing card  508  is spread out farther to the right relative to messaging card  510  than is messaging card  510  relative to photo card  526 . Thus, more of messaging card  510  is revealed on touch screen  112  than photo card  526 ; evidenced by display of the entirety of messaging icon  518  and only a portion of photo icon  528 . Additional cards present in the stack are illustrated as one or more edges  503  displayed under card  528  (e.g., the bottom most card that is partially displayed). 
       FIG. 5F  illustrates an exemplary user interface for the user interface selection mode that displays the user interface representation cards with substantial depth (e.g., in a three-dimensional representation), as if the user is looking down at cards that are sequentially levitating, along a virtual z-axis substantially orthogonal to the plane of the display, from a deck of cards sitting on a table. The cards become larger as they extend further away from the bottom of the stack, giving the appearance that they are travelling substantially towards the user. For example, web browsing card  508  is displayed as larger than messaging card  510  on touch screen  112  because it is further away from the bottom of the stack. As illustrated, multiple cards are viewed as if travelling along a straight or slightly curved path up (e.g., along the virtual z-axis) and to the right from a stack of cards on the left hand side of the display. However, in some embodiments, the cards travel up and to the left from a stack of cards on the right hand side of the display, and/or travel askew or along a non-linear path (e.g., along a curved or seemingly random path). 
       FIGS. 5G-5K  illustrate movement of the user interface representation cards on the display in response to a user input (e.g., navigation between multiple user interface representations) in a substantially two-dimensional representation of the stack. As illustrated in  FIG. 5G , device  100  displays a stack of user interface cards  508 ,  510 , and  526  spread out to the right. Device  100  detects a drag gesture (e.g., a user input) including contact  530  and movement  532  originating from a location of touch screen  112  displaying messaging card  510  (e.g., the user touches and drags messaging card  510 ). 
     In response to detecting movement  532  of contact  530  from location  530 -a in  FIG. 5G  to location  530 -b in  FIG. 5H , and continuing to location  530 -c in  FIG. 5I , the device further spreads out the user interface cards to the right (e.g., in the direct of the drag gesture). As illustrated in  FIGS. 5G-5I , messaging card  510  moves laterally across the screen at the same speed as contact  530  (e.g., is directly manipulated by the contact) from location  510 -a in  FIG. 5G  to location  510 -b in  FIG. 5H , and continuing to location  510 - c in  FIG. 5I , as if the contact was actually pressing down and moving the card on a table. This is illustrated by maintaining a fixed display of card  510  relative to the location of contact  530  on touch screen  112  (e.g., the touch-sensitive surface). For example, the word “Will” in the representation of messaging user interface  507  remains directly under the contact in  FIGS. 5G-5I . 
     As illustrated in  FIGS. 5G-5I , cards displayed above the card being directly manipulated by the contact move faster than the contact. For example, web browsing card  508  moves faster than contact  530 , and thus faster than messaging card  510 , traveling from location  508 -a in  FIG. 5G  to location  508 -b in  FIG. 5H , and eventually off of the screen (e.g., to the right of the right edge of touch screen  112 ) in  FIG. 5I . As a result of the difference in speeds between cards, more of messaging card  510  is revealed from under web browsing card  508  as contact  530  moves to the right. For example, as a result of contact  530  moving from location  530 -a in  FIG. 5G  to location  530 -b in  FIG. 5H , more of the conversation in the representation of user interface  507  is revealed (this is also shown by the appearance of the name “Messages”  520  in title area  522  above card  510  in  FIG. 5H  after being covered by web browsing card  508  in  FIG. 5G ). 
     As illustrated in  FIGS. 5G-5I , cards displayed below the card being directly manipulated by the contact move faster than the contact. For example, photo card  5026  moves slower than contact  530 , and thus slower than messaging card  510 . As a result of the difference in speeds between cards, more of photo card  526  is revealed from under messaging card  510  as contact  530  moves to the right. For example, as a result of contact  530  moving from location  530 -a in  FIG. 5G  to location  530 -b in  FIG. 5H , more of the photographs the representation of user interface  524  are revealed (this is also shown by the gradual appearance of name “Photo”  532  in the title area above card  526  in  FIGS. 5H and 5G ). 
       FIG. 5H  also illustrates revealing of previously hidden music card  534  (e.g., representation  534  or user interface  536  for a music management/playing application) from under photo card  526 , as photo card moves from location  526 -a in  FIG. 5G  (e.g., where it is displayed as sitting on top of all the hidden cards in the stack) to location  526 -b in  FIG. 5H . This movement gives the user the effect that photo card  526  is being slid off the top of the deck of cards, revealing part of the next card (e.g., music card  534 ). 
       FIG. 5J  illustrates lift-off of contact  530  at location  530 -c. As illustrated in  FIGS. 5G-5J , movement of the representation cards across the display stops when movement  532  of contact  530  stops at  FIG. 5I  and lift-off of contact  530  is detected in  FIG. 5J . This is illustrated in  FIG. 5J  by maintaining display of messaging card  510  at location  510 -c, where it was displayed after stopping movement  532  of contact  530  at location  530 -c in  FIG. 5I . 
     The series of  FIGS. 5G, 5H, 5J, and 5K , illustrates lift-off of contact  530  prior to stopping movement  532 . As illustrated in  FIG. 5K , representation cards  510 ,  526 , and  534  continue to move across touch screen  112  (e.g., with diminishing momentum). This is illustrated by the change in location, for example, of messaging card  510  from location  510 -c in  FIG. 5J  (when lift off of contact  530  is detected) to location  510 -d in  FIG. 5K . In some embodiments, continued momentum of a representation card moving across the display occurs in response to a flick gesture (e.g., inertial scrolling of UI representation cards, where the cards move with simulate inertia and slow down with simulate friction and have an initial velocity that is based on a velocity of the contact at a predefined time corresponding to liftoff of the contact from the touch-sensitive surface such as the velocity at liftoff of the contact or the velocity of the contact just before liftoff of the contact). 
       FIG. 5K  also illustrates revealing telephony card  540  (e.g., representation  540  of user interface  542  for a telephony application) as previously hidden music card  534  moves from location  534 -c in  FIG. 5J  to location  534 -d in  FIG. 5K . Thus, in some embodiments, the stack includes more than one hidden card that can be revealed by continuing to navigate the user interface selection mode. 
     Although movement of the cards in response to the drag gesture is illustrated along a straight line in  FIGS. 5G-5K , in some embodiments, movement of the cards may be askew of a predefined axis or path in response to a similarly askew user input. In some embodiments, the path of the cards is fixed along a predefined path and vector components of a movement that are orthogonal to the predefined path (e.g., the downward component to movement of a contact from the upper left hand side to the lower right hand side of a touch-sensitive surface) is ignored when moving display of the cards across the screen. In some embodiments, a vector component of a movement that is orthogonal to a predefined movement path are reflected in the movement of one or more cards across the screen (e.g., the card being directly manipulated by the contact may be pulled up or down from the path of the stack, or the entire path of the stack—e.g., all the cards—may be altered). 
     In some embodiments, a vector component of a movement that is orthogonal to a predefined movement path is ignored when the movement creates an angle with the predefined movement path that is below a threshold angle and is accounted for when the movement creates an angle with the predefined movement path that is above the threshold angle. For example, the movement of one or more representation cards is stabilized when user input movements are askew of the predefined movement path by less than a threshold angle (e.g., 15°), to account for undesired drift in the user&#39;s movement. But, when the user makes an obvious upwards gesture (e.g., at an angle 80° askew of the predefined movement path), one or more representation cards are moved up or down on the display, in correspondence with the orthogonal vector component of the movement (e.g., so that the user can remove a card from the stack while continuing to navigate through the remaining cards). 
       FIGS. 5L-5N  illustrate movement of the representation cards in the opposite direction in response to a user input including movement in the opposite direction.  FIG. 5L  illustrates display of user interface  506  for the user interface selection mode after lift-off of contact  530  in  FIGS. 5I-5J  (e.g., without inertial scrolling). The device detects a second drag gesture (e.g., user input) including contact  546  and movement  548  originating at a location on touch screen  112  displaying messaging card  510  (e.g., the user touches and drags messaging card  510  back towards the base of the stack). 
     In response to detecting movement  548  of contact  546  from location  546 -c in  FIG. 5L  to location  546 -d in  FIG. 5M , and continuing to location  5 N in  FIG. 5N , the device pulls UI representation cards  534 ,  526 ,  510 , and  508  back towards the base of the stack. Messaging card  510  moves laterally across the screen at the same speed as contact  546  (e.g., is directly manipulated by the contact) from location  510 -c in  FIG. 5L  to location  510 -e in  FIG. 5H , and continuing to location  510 -f in  FIG. 51  because the card was displayed at a location corresponding to contact  546 . This is illustrated by maintaining a fixed display of card  510  relative to the location of contact  546  on touch screen  112 . For example, the word “Do” in the representation of messaging user interface  507  remains directly to the upper left of the contact in  FIGS. 5L-5N . 
     As illustrated in  FIGS. 5M-5N , web browsing card  508  moves faster than contact  546  because it is displayed above messaging card  510 . Because messaging card  510  is traveling at the same speed as contact  546 , web browsing card  508  is also traveling faster than messaging card  510 . As a result, web browsing card  508  starts to catch-up to, and cover, messaging card  508 . For example, web browsing card  508  only covers the edge of messaging card  510  in  FIG. 5M . Web browsing card  508  starts to slide over messaging card  510  with continued movement  548  of contact  546  to the left on the display, covering half of messaging card  510  in  FIG. 5N . 
     As illustrated in  FIGS. 5M-5N , photo card  526  moves slower than contact  546  because it is displayed above messaging card  510 . Because messaging card  510  is traveling at the same speed as contact  546 , photo card  526  is also traveling slower than messaging card  510 . As a result, messaging card  510  starts to catch-up to, and cover, photo card  546 . For example, application name “Photo”  532  associated with photo card  526  is completely exposed in  FIG. 5L . Message card  510  gradually slides further over photo card  526  with continued movement  548  of contact  546  to the left on the display, completely eclipsing application name “Photo”  532  when contact  546  reaches location  546 -f in  FIG. 5N . 
       FIG. 5O  illustrates the speed of user interface representation cards relative to the lateral speed of contacts  530  and  546 , as illustrated in  FIGS. 5G-5I and 5L-5N  on touch screen  112 . As illustrated in the top panel, contact  530  moves left to right across touch screen  112  at a constant speed equal to the slope of movement  532  (e.g., graphically represented as a function of pixels over time). After lift-off of contact  530  at location  530 -c, the device detects contact  546 , moving back right to left across touch-sensitive screen  112  at a constant speed equal to the slope of movement  548  (e.g., graphically represented as a function of pixels over time. Because contacts  530  and  546  are detected at locations on touch screen  112  corresponding to display of messaging card  510 , the speed of messaging card  510  is equal to the speed of the contact. 
     The middle panel of  FIG. 5O  illustrates the relative speeds of the UI representation cards along speed curve  550 , when at location “e” during movement  548  of contact  546  (e.g., as illustrated in  FIG. 5M ). The relative lateral speed of messaging card  510  when at location  510 -f is equal to the absolute value of the slope of movement  548 , as graphically illustrated in the top panel of  FIG. 5O . Because web browsing card  508  was at a relative Z-position that is above (e.g., along the virtual Z-axis substantially orthogonal to the plane of the display of the device) messaging card  510  in user interface  506  (e.g., an exemplary user interface for the user interface selection mode), speed curve  550  shows that web browsing card  508  is traveling relatively faster than messaging card  510 . Similarly, because photo card  526  has a relative Z-position that is below messaging card  510  in user interface  506 , speed curve  550  shows that the photo card  526  is travelling slower than messaging card  510 . 
     The absolute lateral speeds of representation cards  526 ,  510 , and  508  are relative to the actual speed of the user gesture (e.g., the lateral component of a user&#39;s contact moving across the touch-sensitive surface). As shown in the middle panel of  FIG. 5O , user contact  546  is directly manipulating movement of messaging card  510  because the contact is at a location on touch screen  112  corresponding to display of messaging card  510 , Thus, the speed of messaging card  510  is the speed of the user contact. The lateral speed of web browsing card  508  is equal to a factor of the speed of the user contact, e.g., equal to the speed of the user contact multiplied by a coefficient, where the coefficient is larger than  1  (e.g., because web browsing card  508  has a higher z-position relative to messaging card  510 , which is being directly manipulated by user contact  546 ). The lateral speed of photo card  526  is also equal to a factor of the speed of the user contact, e.g., equal to the speed of the user contact multiplied by a coefficient, where the coefficient is smaller than 1 (e.g., because photo card  526  has a lower z-position relative to messaging card  510 , which is being directly manipulated by user contact  546 ). 
     The middle panel of  FIG. 5O  also illustrates, as in some embodiments, the level of blurring applied to each card in the stack is relative to the absolute z-position of the card. Thus, as cards are spread out (e.g., to the right) from the stack, their absolute z-position increases and the blur applied decreases. In some embodiments, the device applies a dynamic change in blurring to a particular card as its absolute z-position is manipulated by a user input. 
     As illustrated in  FIG. 5M-5N , when moving in the opposite direction of the original gesture (e.g., back towards the base of the stack), web browsing card  508  catches up to contact  546  because it is travelling faster, as illustrated in  FIG. 5O . Web browsing card  508  moves between contact  546  and messaging card  510  when the leading edge (the left edge) of web browsing card  508  is displayed at location  508 -f on touch screen, corresponding to the centroid of contact  546  at location  546 -f. At this point, contact  546  begins to directly manipulate web browsing card  508 , rather than messaging card  510 . 
     As illustrated in  FIGS. 5N and 5HH , device  100  detects continuation of movement  548  of contact  546  from location  546 -f in  FIG. 5N  to location  546 -g in  FIG. 5HH . In response, web browsing card  508  continues to move laterally across the screen back towards the base of the stack (e.g., from location  508 -f in  FIG. 5N  to location  5 -g in  FIG. 5HH ) at the same speed as contact  546  (which is now directly manipulating web browsing card  508  rather than messaging card  510 ), as indicated by maintaining a fixed display of card  508  relative to the location of contact  546  on touch screen  112 . 
     As illustrated in the lower panel of  FIG. 5O , the speed of UI cards  526 ,  510 , and  508  slow down when this handoff occurs. Web browsing card  508  moves at a speed corresponding to the speed of contact  546  when displayed at location  508 -f (e.g., as in  FIG. 5N ), as did messaging card  510  when it was displayed at location  510 -e (e.g., as in  FIG. 5M , and as shown in the middle panel of  FIG. 5O ). Similarly, messaging card  508  travels at the same lower relative speed when displayed at location  510 -f (e.g., as in  FIG. 5N ) as did photo card  526  when displayed at  526 -e (e.g., as in  FIG. 5M ), because it is now the card below the card under contact  546 . Finally, photo card  526  moves at a slower speed when displayed at location  526 -f (e.g., as in  FIG. 5N ) than it did when displayed at location  526 -e (e.g., as in  FIG. 5M ). Although the movements of the UI cards are illustrated at constant speeds, the speeds of the cards are relative to the speed of the user input. Thus, the electronic device moves the UI cards at variable speeds in response to detecting a user input gesture with variable speed. 
     Speed curve  5550  is an exemplary representation of the relationship between the speeds of the respective UI representation cards displayed in the stack. A first card (e.g., web browsing card  508 ) displayed above a second card (e.g., messaging card  510 ) in relative Z-position (e.g., along the virtual z-axis) will always travel faster than the second card. In some embodiments, speed curve  550  is representative of other variable manipulations in the display of the UI representation cards. For example, the level of blurring applied to a respective card in the stack (e.g., cards displayed further down in the stack are more blurry than cards displayed towards the top of the stack), the size of a respective card in the stack (e.g., in user interface selection mode user interfaces displaying the stack as a three-dimensional representation, cards displayed further down in the stack appear smaller than cards displayed towards the top of the stack), or the lateral position of a respective card in the stack (e.g., in user interface selection mode user interfaces displaying the stack as a substantially two-dimensional representation, cards displayed further down in the stack appear closer to the base of the stack than cards displayed towards the top of the stack). 
     In some embodiments, the spacing of points on speed curve  550  (e.g., corresponding to placement of UI representation cards relative to one another) have a constant difference in ordinate value (e.g., the change in the z-dimension, as represented by the vertical difference, between two points is the same). In some embodiments, as illustrated in  FIG. 5O , where speed curve  550  follows a concave function, there is an increasing difference in the perpendicular distance between successive points (e.g., larger changes in the x direction). For example, the difference between the relative Z-positions of photo card  526  and messaging card  510  is the same as the difference between the relative Z-positions of messaging card  510  and web browsing card  508 . However, the difference between the lateral speeds of messaging card  510  and web browsing card  508  is greater than the difference between the lateral speeds of photo card  526  and messaging card  510 . This causes a visual effect on the display that the top card displayed on a stack will quickly move off the screen relative to the revealing of cards displayed further back in the stack. 
       FIGS. 5P-5T  illustrate movement of user interface representation cards on the display in response to a user input (e.g., navigation between multiple user interface representations) in a substantially three-dimensional representation of the stack. As illustrated in  FIG. 5P , device  100  displays a stack of user interface cards  508 ,  510 , and  526  which appear to be spreading up from a stack of cards set behind the device. Web browsing card  508  is offset to the right, partially covers messaging card  510 , and is displayed larger than messaging card  510  (e.g., to simulating that it is positioned above messaging card  510  in a virtual z-dimension substantially orthogonal to the plane of touch screen  112 ). Messaging card  510  and photo card  526  are displayed as increasingly blurred relative to web browsing card  508  (e.g., further simulating distance in the display).  FIG. 5Q  additionally illustrates display of home screen card  554  (e.g., representation  554  of a user interface  552  for a home screen on the device). 
     As illustrated in  FIG. 5R , device  100  detects a flick gesture (e.g., a user input) including contact  556  and movement  558  originating from a location of touch screen  112  displaying messaging card  510  (e.g., the user touches and drags messaging card  510 ). In response to detecting movement  558  of contact  556  from location  556 -a in  FIG. 5G  to location  556 -b in  FIG. 5H , and continuing to location  556 -c in  FIG. 5I , the device moves the cards away from the base of the stack and towards the screen along the virtual z-axis. For example, messaging card  510  gets larger and moves to the right as it moves from location  510 -a in  FIG. 5R  to location  510 -b in  FIG. 5  S, and continues to get larger as it moves off the screen to the right at location  510 -c in  FIG. 5T . 
       FIG. 5T  illustrates detection of the lift-off of contact  556  at location  556 -c without stopping movement  558 , consistent with a flick gesture. Messaging card  510 , which was traveling with contact  556  (e.g., as the same speed; being directly manipulated by contact  556 ), continues to move on the display with simulated inertia, finally stopping at location  510 -c on touch screen  112 . 
       FIGS. 5R-5T  also illustrate a change in the level of blurring applied to UI representation cards as they move away from the base of the stack. For example, photo card  526  is moderately blurry when first displayed at location  526 -a as the bottom card visible in the stack. As photo card  526  moves from location  526 -a in  FIG. 5R  to location  526 -b in  FIG. 5S  (e.g., in response to movement  558  of contact  556  from location  556 -a in  FIG. 5R  to location  556 -b in  FIG. 5S ), and eventually to location  556 -c in  FIG. 5T , it gradually comes into focus (e.g., becomes less blurry). In some embodiments, the level of blur applied to a UI representation card follows a similar relationship to that of lateral speed relative to the card&#39;s Z-position, as illustrated in speed curve  550  in  FIG. 5O . 
       FIGS. 5U-5W  illustrate insertion of a user interface representation card for a transient application activated while the device is in a user interface selection mode.  FIG. 5U  illustrates user interface  506  for a user interface selection mode displaying a stack of user interface cards  508 ,  510 ,  526 , and  534 , being navigated by a user. Device  100  then receives a phone call and in response, as illustrated in  FIGS. 5V-5W , shuffles telephony card  554  (e.g., representation  554  of user interface  556  for a received call within a telephony application) into the stack at location  555 -b, as illustrated in  FIG. 5W . As illustrated in  FIGS. 5V-5W , the device moves web browsing card  508  and messaging card  510  up in the stack to (e.g., from locations  508 -b and  510 -b, represented as dashed outlines in  FIG. 5V  off the display and to location  510 -e in  FIG. 5W , respectively) to make room for telephony card  556 . Although  FIGS. 5V-5W  illustrate an animation where telephony card  555  is brought into the screen, in  FIG. 5V , and inserted into the stack, in  FIG. 5W , behind web browsing card  508  and messaging card  510 , other animations and placement for the user interface representation of the transient application are contemplated (e.g., the new card becomes the top of the stack or cards further back in the stack are pushed further down to make room for the new card). 
       FIGS. 5X-5AA  illustrate removal of a user interface representation card upon detection of a predefined user input.  FIG. 5X  illustrates user interface  506  for a user interface selection mode displaying a stack of user interface cards  508 ,  510 ,  526 , and  534 , being navigated by a user. Device  100  detects a swipe gesture including contact  560  and movement  562  substantially orthogonal to the predefined movement path of the cards in the stack (e.g., the swipe moves up touch screen  112 , while cards in the stack move right and left across the screen when navigating), originating from a location of touch screen  112  displaying messaging card  510 . In response to detecting movement  562  of contact  560  from location  560 -a in  FIG. 5X  to location  560 -b in  FIG. 5Y , and continuing to location  560 -c in  FIG. 5Z , the device lifts messaging card  510  out of the stack and sends it off of the screen (e.g., via movement from location  510 -b in  FIG. 5X  to location  510 -f in  FIG. 5Y , continuing to location  510 -g in  FIG. 5Z ). 
     As illustrated in  FIGS. 5Z-5AA , device  100  moves photo card  526  and music card  534  up in the stack after messaging card  510  is removed. Photo card  526  is moves from location  526 -g in  FIG. 5Z  to location  526 -h in  FIG. 5AA , replacing the hole in the stack caused by removal of messaging card  510 . Likewise, music card  534  moves from location  534 -g in  FIG. 5Z  to location  534 -h in  FIG. 5AA , replacing the hole in the stack caused when photo card  526  moved up in the stack. The level of blurring applied to photo card  526  and music card  534  is also adjusted in accordance with their movement up in the stack. For example, photo card  526  is partially blurry when displayed at location  526 -g in  FIG. 5Z , but in focus when displayed at location  526 -h in  FIG. 5AA . In some embodiments, removal of the user interface representation card from the stack also closes an active application associated with the user interface. 
       FIGS. 5BB and 5CC  illustrate leaving the user interface selection mode by selecting a user interface representation.  FIG. 5BB  illustrates user interface  506  for a user interface selection mode displaying a stack of user interface cards  508 ,  510 ,  526 , and  534 , being navigated by a user. Device  100  detects a tap gesture including contact  564  at a location on touch screen  112  displaying messaging card  510  (e.g., representation  510  of user interface  507  for a messaging application). In response to detecting the tap gesture, the device activates the messaging application associated with user interface  507  and changes the display on touch screen  112  from user interface  506  for the user interface selection mode to user interface  507  for the messaging application, as illustrated in  FIG. 5CC . 
       FIG. 5DD  illustrates visual effects applied to a title area associated with a first user interface representation card as the user interface representation card displayed above the first card moves into close proximity.  FIG. 5DD  illustrates messaging card  510  displayed over photo card  526  in user interface  506  of a user interface selection mode that includes a substantially two-dimensional representation of the stack. Photo card  526  is associated with title bar  558  including name “Photos”  532  and icon  526  for the image management application associated with user interface  524 . Messaging card  510  is associated with title bar  522  displaying information related to the messaging application associated with user interface  507 . Display of messaging card  510  gradually slides over photo card  526  over time (via movement from location  510 -a in the top panel, through locations  510 -b and  510 -c in the middle panels, to location  510 -d in the bottom panel of  FIG. 5DD ). As the edge of messaging title bar  522  approaches display of name “Photos”  532  on photo title bar  558  (when messaging card  510  is at location  508 -b in the second panel), the device applies a transitional fading of name “Photos”  532 . Panel three of  FIG. 5DD  illustrates that display of name “Photos”  532  is removed prior to messaging title bar  522  eclipsing its previous location on photo title bar  558 . 
     Similarly, as the edge of messaging title bar  522  approaches display of icon  528  associated with the image management application on photo title bar  558  (when messaging card  510  is at location  508 -d in the bottom panel of  FIG. 5DD ), the device applies a transitional fading of icon  528 , such that display of icon  528  is removed from the display prior messaging title bar  522  eclipsing its previous location on photo title bar  558 . In some embodiments, e.g., where the user interface selection mode includes a substantially three-dimensional representation of the stack, it the edge of the second user interface representation card (e.g., the card on top), rather than the associated title bar, that approaches, and triggers the animation removing, display of the title information associated with the first user interface representation card (e.g., the card on bottom). In certain embodiments, the animation applied to the information displayed in the title area (e.g., title bar) is a blurring or clipping, rather than the fading illustrated in  FIG. 5DD . In some embodiments, the icons stack up, rather than disappear, when the next user representation card approaches. 
       FIGS. 6A-6V  illustrate exemplary user interfaces for navigating between user interfaces in accordance with some embodiments. The user interfaces in these figures are used to illustrate the processes described below, including the processes in  FIGS. 10A-10H, 11A-11E, 12A-12E, 13A-13D, 14A-14C, 15, 24A-24F, and 25A-25H . Although some of the examples which follow will be given with reference to inputs on a touch-screen display (where the touch-sensitive surface and the display are combined), in some embodiments, the device detects inputs on a touch-sensitive surface  451  that is separate from the display  450 , as shown in  FIG. 4B . 
       FIGS. 6A-6V  illustrate exemplary embodiments of a user interface selection mode that allows a user to peek at representations of previously displayed user interfaces without leaving a current user interface, allow a user to quickly toggle between two respective user interfaces, and allow a user to easily enter into user interface selection modes with different types of hierarchal selections on an electronic device (e.g., multifunction device  100 ). Exemplary user interfaces (e.g., user interface  506  displayed on touch screen  112 ) for the user interface selection mode include representations of multiple user interfaces (e.g., representations  508 ,  510 ,  526 ,  534 ,  540 , and  552  of user interfaces  502 ,  507 ,  524 ,  536 ,  542 , and  552 , respectively) for applications associated with the electronic device displayed as a virtual stack of cards (e.g., the “stack”) or as a choice between the two most recently displayed user interfaces. User inputs (e.g., contacts, swipe/drag gestures, flick gestures, etc.) detected on touch screen  112  (e.g., a touch-sensitive surface) are used to navigate between user interfaces that can be selected for display on the screen (e.g., touch screen  112 ). 
       FIGS. 6A-6G  illustrate an embodiment where a user operating an electronic device displaying a first user interface (e.g., any user interface for a respective application open on the device, such as a web browsing user interface) can navigate between (i) peeking at a previously displayed user interface and reverting back to the first user interface, (ii) changing to a previous application, (iii) entering a user interface selection mode (e.g., an application selection mode), and (iv) scrolling through user interfaces within a user interface selection mode with differential gestures starting from a common contact on a touch-sensitive surface (e.g., touch screen  112  on multifunction device  100 ). 
       FIGS. 6A-6D  illustrate an embodiment where a user views (e.g., “peeks” at) a representation of a previously displayed user interface and then automatically reverts back to the user interface that was displayed on the device before peeking (e.g., reverts back to the application that was open on the device).  FIG. 6A  illustrates display of a graphical user interface  502  for a web browsing application on the electronic device. 
     As illustrated in  FIGS. 6B-6C , the device enters a user interface preview mode upon detection of a user input including contact  602  adjacent to the left edge of touch screen  112  (e.g., on the bezel) with an intensity below a predetermined threshold (e.g., below deep press intensity threshold (IT D ); e.g., an exemplary predetermined input). While detecting the input including contact  602 , the device replaces display of web browsing user interface  502  on touch screen  112 , as illustrated in  FIG. 6B , with display of user interface selection mode  506 . User selection mode  506  includes user interface representation of the last two user interfaces displayed on touch screen  112 , e.g., representation  508  of web browsing user interface  502  and representation  510  of messaging user interface  507 . As illustrated in  FIGS. 6B and 6C , the intensity of contact  602  is maintained below a deep press intensity threshold (IT D ) (e.g., an exemplary predetermined intensity threshold), and the contact is stationary at the original detection point. 
     Device  100  then detects termination of the user input including contact  602  in  FIG. 6D . Because the intensity of contact  602  was maintained below a deep press intensity threshold (IT D ), and because the user input did not include movement of contact  602  (e.g., movement in a predefined direction on touch screen  112 ), device  100  reverts the display back to web browsing user interface  502  upon detection of termination (e.g., lift off) of contact  602  by replacing display of user interface  506  with display of user interface  502 . 
       FIGS. 6A, 6E-6G  illustrate an alternate embodiment where a user views (e.g., “peeks” at) a representation of a previously displayed user interface and selects display of the previously displayed user interface, rather than reverting back to the user interface that was displayed on the device before peeking.  FIG. 6A  illustrates display of a graphical user interface  502  for a web browsing application on the electronic device. 
       FIG. 6E  illustrates that the device enters a user interface preview mode upon detection of a user input including contact  604  adjacent to the left edge of touch screen  112  (e.g., on the bezel) with an intensity below a predetermined threshold (e.g., below deep press intensity threshold (IT D ); e.g., an exemplary predetermined input). While detecting the input including contact  604 , the device replaces display of web browsing user interface  502  on touch screen  112 , with display of user interface selection mode  506 . User selection mode  506  includes user interface representation of the last two user interfaces displayed on touch screen  112 , e.g., representation  508  of web browsing user interface  502  and representation  510  of messaging user interface  507 . As illustrated in  FIGS. 5B and 5C , the intensity of contact  604  is maintained below a deep press intensity threshold (IT D ) (e.g., an exemplary predetermined intensity threshold). However, electronic device detects movement  606  of contact  604  in a predefined direction (e.g., laterally across touch screen  112 ) from location  604 -a in  FIG. 6E  to location  604 -b in  FIG. 6F . 
     Device  100  then detects termination of the user input including contact  604  in  FIG. 6D . Because the intensity of contact  604  was maintained below a deep press intensity threshold (IT D ), and because the user input included movement of contact  604  in a predefined direction on touch screen  112  (e.g., laterally across the display), device  100  replaces display user interface  506  with display of user interface  507  for a messaging application, rather than reverting back to web browsing user interface  502 , as illustrated in  FIG. 6D . 
     Thus, in some embodiments, when a user input invoking the user interface preview mode has a characteristic intensity (e.g., a maximum intensity for the duration of the input below a predetermined threshold) a user can distinguish between reverting back to display of the user interface displayed immediately preceding entry into the user interface preview mode (e.g., when the user is just peeking at a previously displayed user interface) and changing the display to the previously displayed user interface by moving the contact associated with the gesture in a predetermined direction or not (e.g., keeping the contact stationary). 
       FIGS. 6A, 6H-6I  illustrate another alternate embodiment where a user views (e.g., “peeks” at) a representation of a previously displayed user interface and selects to stably enter a user interface selection mode, rather than reverting back to display of either of the previously displayed user interfaces represented during the user&#39;s peek.  FIG. 6A  illustrates display of a graphical user interface  502  for a web browsing application on the electronic device. 
     As previously illustrated in  FIGS. 6C and 6E , the device enters a user interface preview mode upon detection of a user input including a contact adjacent to the left edge of touch screen  112  (e.g., on the bezel) with an intensity below a predetermined threshold (e.g., below deep press intensity threshold (IT D ); e.g., an exemplary predetermined input).  FIG. 6H  further illustrates that upon detection of an increase in the intensity of the invoking contact (e.g., contact  608  in  FIG. 6H ), the device enters a stable user interface selection mode. Upon entering the stable user interface selection mode, device  100  displays a stack of user interface representation cards on touch screen  112 , including user interface representations  508 ,  510 , and  526  displayed in relative Z-positions (e.g., as described for  FIGS. 5A-5HH ). 
     Device  100  then detects termination of the user input including contact  608  in  FIG. 6I . Because the intensity of contact  608  exceeded a predetermined intensity threshold (e.g., deep press intensity threshold (IT D )) for invoking a stable user interface mode, device  100  does not replace the display of user interface  506  on touch screen  112 . In some embodiments, further navigation within the stable user interface selection mode is performed as described for  FIGS. 5A-5HH . 
     Thus, in some embodiments, the user can further distinguish between peeking and selecting one of a limited number of user interfaces displayed in a user interface selection preview mode for display on touch screen  112  and entering a stable user interface selection mode with further navigational controls based on the intensity of the contact used to invoke the user interface selection preview mode. 
       FIGS. 6J-6L  illustrate an embodiment in which the user directly manipulates display of a user interface selection mode by increasing the intensity of a user input.  FIG. 6J  illustrates entry into a stable user interface selection mode, including display of a stack of user interface representation cards (e.g., user interface representations  508 ,  510 , and  526  displayed in relative Z-positions with each other, e.g., as described for  FIG. 5A-5HH ) in user interface  506  by detection of contact  610  adjacent to the left edge of touch screen  112  (e.g., on the bezel) with an intensity exceeding a predetermined intensity threshold (e.g., deep press intensity threshold (IT D )). 
       FIGS. 6K-6L  illustrate that when device  100  detects further increases in the intensity of contact  610 , user interface representation cards displayed in the stack are spread-out (e.g., along a z-axis substantially orthogonal to the plane of the display) based on direct manipulation of the contact intensity by the user. In some embodiments, as illustrated in  FIGS. 6K-6L , a small change in intensity (e.g., from an intensity detected just below the top tick mark in  FIG. 6K  to an intensity detected just above top tick mark in  FIG. 6L ) causes movement of messaging card  510  from location  510 -b in  FIG. 6K  to location  510 -c in  FIG. 6L , revealing more of photo card  526  and music card  534  in  FIG. 6L . 
       FIGS. 6M-6P  illustrate an embodiment where device  100  distinguishes between user inputs made within an application user interface based on a characteristic intensity of the user input.  FIG. 6M  illustrates display of a graphical user interface  502  for a web browsing application on the electronic device. User interface  502  includes application-specific “back” button icon  614  for navigating to a previously displayed user interface (e.g., a previous web page displayed on touch screen  112 ) within the application. Device  100  detects a deep press including contact  612  having a characteristic intensity exceeding a predetermined intensity threshold (e.g., deep press intensity threshold (IT D )) at a location on touch screen  112  corresponding to display of “back” button icon  614 . In response to detecting the deep press, device  100  replaces display of web browsing user interface  502  on touch screen  112  with user interface  506  for a user interface selection mode that includes user interface representations  508 ,  618 , and  622  of previously viewed web browsing interfaces  502 ,  616 , and  620  (e.g., previously viewed web pages in a hierarchy of the browser history) in  FIG. 6N . 
     Alternatively, device  100  detects a swipe gesture (e.g., movement  632  of contact  630 ) originating at the edge of touch screen  112  in  FIG. 6V . In response, device  100  navigates backwards in an application-specific user interface hierarchy (e.g., navigates back to the last webpage viewed in the web browsing application) and replaces display of user interface  502  in  FIG. 6V  with user interface  616  in  FIG. 6P . In some embodiments, device  100  applies a dynamic animation upon detection of the edge swipe, for example, animating slide of user interface  502  off the screen, gradually revealing previously displayed user interface  616 , as if stacked below user interface  502 . In some embodiments, the animation is directly manipulated by the progress of the user swipe gesture. Thus,  FIGS. 6V and 6P  illustrate using an edge swipe gesture (e.g., including movement  632  of contact  630 ) to navigate back in an application-specific user interface hierarchy. 
       FIG. 60  also illustrates display of a graphical user interface  502  for a web browsing application on the electronic device. User interface  502  includes application-specific “back” button icon  614  for navigating to a previously displayed user interface (e.g., a previous web page displayed on touch screen  112 ) within the application. Device  100  detects a tap gesture (rather than a deep press as illustrated in  FIG. 6M ) including contact  624  having a characteristic intensity below a predetermined intensity threshold (e.g., deep press intensity threshold (IT D )). In response to detecting the tap gesture, device  100  replaces display of web browsing user interface  502  on touch screen  112  with web browsing user interface  616  for a previously viewed user interface in the associated web browsing application (e.g., the last web page visited in the web browsing application), as illustrated in  FIG. 6P . Thus, in some embodiments, an electronic device distinguished between application-specific user interface inputs based on a characteristic intensity of the user input. 
       FIGS. 6Q-6S  illustrate that after toggling between a first user interface and a second user interface through the user interface preview mode, as described for  FIGS. 6A, 6E-6G , a user may quickly toggle back to the first user interface by repeating the user gesture while the device displays the user interface for the second application. 
       FIG. 6Q  illustrates that after detecting lift off the user gesture that caused the device to change the user interface display to second user interface  507  for a messaging application, the device detects a second user input including contact  626  adjacent to the left edge of touch screen  112  (e.g., on the bezel) with an intensity below a predetermined threshold (e.g., below deep press intensity threshold (IT D ); e.g., an exemplary predetermined input). While detecting the input including contact  626 , the device replaces display of messaging user interface  507  on touch screen  112 , with display of user interface selection mode  506 . As illustrated in  FIG. 6R , user selection mode  506  includes user interface representation of the last two user interfaces displayed on touch screen  112 , e.g., representation  508  of web browsing user interface  502  and representation  510  of messaging user interface  507 . However, the relative order of representation  508  and  510  in user interface  506  is switched, as compared to display of the user interface  506  in  FIGS. 6E-6F , because messaging user interface  507  is now the most recently displayed user interface on touch screen  112 , and is thus representation  510  of user interface  507  is displayed over representation  508  of user interface  502  in  FIG. 6R . 
     As illustrated in  FIGS. 6Q and 6R , the intensity of contact  626  is maintained below a deep press intensity threshold (IT D ) (e.g., an exemplary predetermined intensity threshold). However, electronic device detects movement  628  of contact  626  in a predefined direction (e.g., laterally across touch screen  112 ) from location  626 -a in  FIG. 6R . Device  100  then detects termination of the user input including contact  626  in  FIG. 6S . Because the intensity of contact  626  was maintained below a deep press intensity threshold (IT D ), and because the user input included movement of contact  626  in a predefined direction on touch screen  112  (e.g., laterally across the display), device  100  replaces display of user interface  506  with display of user interface  502  for a web browsing application, rather than reverting back to messaging user interface  507 , as illustrated in  FIG. 6Q . Thus, the user has toggled back to the first user interface displayed on touch screen  112  in  FIG. 6A . 
       FIGS. 6T-6U  illustrate an embodiment where device  100  distinguishes between user inputs made a first predefined location with user inputs made at a second predefined location on device  112 .  FIG. 6T  illustrates display of a graphical user interface  502  for a web browsing application on the electronic device. Device  100  detects a deep press including contact  628  having a characteristic intensity exceeding a predetermined intensity threshold (e.g., deep press intensity threshold (IT D )) adjacent to the right edge of touch screen  112  (e.g., on the bezel; a second predefined location). In response to detecting the deep press, device  100  replaces display of web browsing user interface  502  on touch screen  112  with web browsing user interface  616  for a previously displayed website on touch screen  112 , as illustrated in  FIG. 6U . 
     This is in contrast with the detection of a deep press input in  FIG. 6H  adjacent to the left edge of touch screen  112  (e.g., on the bezel; at a first predefined location), which caused device to enter a stable user interface selection mode. Thus, in some embodiments, different operations are performed depending on whether an invoking gesture is detected within a first predefined location or a second predefined location on the touch-sensitive surface. 
       FIGS. 7A-7O  illustrate exemplary user interfaces for navigating between user interfaces in accordance with some embodiments. The user interfaces in these figures are used to illustrate the processes described below, including the processes in  FIGS. 10A-10H, 11A-11E, 12A-12E, 13A-13D, 14A-14C, 15, 24A-24F, and 25A-25H . Although some of the examples which follow will be given with reference to inputs on a touch-screen display (where the touch-sensitive surface and the display are combined), in some embodiments, the device detects inputs on a touch-sensitive surface  451  that is separate from the display  450 , as shown in  FIG. 4B . 
       FIGS. 7A-7O  illustrate exemplary embodiments for navigating between previously displayed user interfaces using a single touch gesture on a predefined area of a touch-sensitive surface (e.g., a touch-sensitive display or touch-sensitive track pad separate from the display) in accordance with some embodiments. In some embodiments, a user toggles between the two most recently viewed user interfaces using touch gestures of varying intensities at one or more predefined areas on a touch-sensitive surface. 
       FIGS. 7A-7F  illustrate an embodiment where a user previews (e.g., “peeks” at) a representation of a previously displayed user interface using a touch gesture with a first characteristic intensity at a predefined area of a touch-sensitive surface, and then open the user interface (e.g., opens the application) by increasing the intensity of the touch gesture to a second characteristic intensity.  FIG. 7A  illustrates display of a graphical user interface  502  for a web browsing application on the electronic device. 
       FIG. 7B  illustrates detection of a touch gesture, including contact  702 , adjacent to the left edge of touch screen  112  (e.g., on the bezel; at a predefined position on the touch-sensitive surface), with a first characteristic intensity (e.g., exceeding a light press intensity threshold (IT L ), but below a deep press intensity threshold (IT D )). In response to detecting the touch gesture, device  100  enters a user interface selection mode, replacing display of web browsing user interface  502  on touch screen  112  in  FIG. 7B  with display of user interface  506  for the user interface selection mode on touch screen  112  in  FIG. 7C . 
       FIG. 7C  illustrates display of user interface  506  for the user interface selection mode, including representation  508  of web browsing user interface  502  (“web browsing card  508 ”) and representation  510  of messaging user interface  507  (“messaging card  510 ”) of two user interfaces previously displayed on touch screen  112 . In some embodiments, the two representations are for the last two user interfaces displayed on the device (e.g., the last two applications open on the display). In some embodiments, the two representations are for the last two user interfaces displayed for the particular application open on touch screen  112  at the time the user interface selection mode was initiated (e.g., the last two web pages displayed in a web browser application or the last two messages displayed in an email management application). 
     As illustrated in  FIG. 7C , web browsing card  508  is displayed as if above messaging card  510  in Z-orientation (e.g., positioned along a virtual axis substantially orthogonal to the plane of the display), and laterally displaced to the right of messaging card  510 , because it represents the last user interface displayed on touch screen  112  prior to activation of the user interface selection mode. Device  100  also applies a level of blurring to messaging card  510  (e.g., associated with its relative or absolute Z-position). In some embodiments, the representation of the last user interface displayed prior to activation of the user interface selection mode is displayed behind or equal with the second user interface representation in relative Z-orientation. 
       FIG. 7D  illustrates detection of increased intensity of contact  702  (e.g., from an intensity just above a light press intensity threshold IT L  in  FIG. 7C  to an intensity just below a deep press intensity threshold IT D  in  FIG. 7D ). In response to detection of the increased intensity of contact  702 , messaging card  510  increases in size and moves towards the plane of the touch screen  112  in the virtual z-dimension (e.g., from location  510 -a in  FIG. 7C  to location  510 -b in  FIG. 7D ). Messaging card  510  also begins to come into focus (e.g., the level of blurring is reduced) as it moves up in the virtual z-dimension. Concurrently, web browsing card  508  decreases in size and moves backwards in the virtual z-dimension (e.g., from location  508 -a in  FIG. 7C  to location  508 -b in  FIG. 7D ). In some embodiments, an animation is displayed to show movement of the first user interface representation and the second user interface representation in a manner that dynamically responds to small changes in the intensity of the contact. 
       FIG. 7E  illustrates detection further increased intensity of contact  702  (e.g., exceeding deep press intensity threshold (IT D )). In response to detection that the intensity of contact  702  exceeds a second characteristic intensity (e.g., exceeding deep press intensity threshold (IT D )), messaging card  510  continues to move up in the virtual z-dimension and moves over web browsing card  508 , which continues to move backwards in the virtual z-dimension and starts to become blurry. 
     In some embodiments, in response to detecting an intensity of contact  702  in excess of a second predetermined threshold (e.g., deep press intensity threshold (IT D )), the device automatically opens the messaging application associated with user interface  507  (e.g., the card or associated application “pops”), and replaces display of the user interface selection mode with user interface  507 , as illustrated in  FIG. 7F . 
       FIGS. 7G-7K  illustrate an alternative embodiment for “peeking” and “popping” previously displayed user interfaces (e.g., and associated applications), as described for  FIGS. 7A-7F . In this embodiment, the user interface representations are displayed in a substantially two-dimensional view, rather than along a virtual z-axis. 
       FIG. 7G  illustrates detection of a touch gesture, including contact  704 , adjacent to the left edge of touch screen  112  (e.g., on the bezel; at a predefined position on the touch-sensitive surface), with a first characteristic intensity (e.g., exceeding a light press intensity threshold (IT L ), but below a deep press intensity threshold (IT D )). In response to detecting the touch gesture, device  100  enters a user interface selection mode, displaying user interface  506  for the user interface selection mode on touch screen  112  in  FIG. 7G . 
       FIG. 7G  illustrates display of user interface  506  for the user interface selection mode, including representation  508  of web browsing user interface  502  (“web browsing card  508 ”) and representation  510  of messaging user interface  507  (“messaging card  510 ”) of two user interfaces previously displayed on touch screen  112 . As illustrated in  FIG. 7G , messaging card  510  is displayed as if right on top of web browsing card  508  in Z-orientation, and laterally displaced to the right of web browsing card  508 , because it represents the last user interface displayed on touch screen  112  prior to activation of the user interface selection mode. 
       FIG. 7H  illustrates detection of increased intensity of contact  704  (e.g., from an intensity just above a light press intensity threshold IT L  in  FIG. 7C  to an intensity just below a deep press intensity threshold IT D  in  FIG. 7D ). In response to detection of the increased intensity of contact web browsing card  508  is further revealed from under messaging card  508  by movement of messaging card  510  to the right of the screen, from location  510 -a in  FIG. 7G  to location  510 -b in  FIG. 7H . 
       FIG. 7E  illustrates detection of a decrease in intensity of contact  704 . In response to detection that the intensity of contact  702  decreases, messaging card  510  begins to slide back over web browsing card  508 . 
       FIG. 7J  illustrates detection of a further decrease in intensity of contact  704  below a first characteristic intensity (e.g., below light press intensity threshold (IT L )). In response to falling below the first characteristic intensity, device  5100  exits user interface selection mode and replaces display of user interface  506  with user interface  507  for the messaging application which was displayed immediately preceding entry into the user interface selection mode (e.g., because contact  704  failed to “pop” web browsing card  508  out from under messaging card  510 , the device reverts into it last active state upon exiting the user interface selection mode).  FIG. 7K  further illustrates detection of lift off of contact  704 , resulting in no change in the user interface displayed on touch screen  112 . 
     In contrast, Figures illustrate an embodiment where, after the user toggled user interface from web browsing user interface  502  to messaging user interface  507  (e.g., as described in  FIGS. 5A-5F ) the user starts the “peek” and “pop” processes again with detection of contact  706  in the predetermined area on the touch sensitive surface (e.g., the left side of the bezel) in  FIG. 7L . In response to detecting increasing intensity contact  706  from  FIG. 7M to 7M , messaging card moves from location  510 -d in  FIG. 7M  to position  510 -e in  FIG. 7N . Detection of a further increase in the intensity of contact  706  in excess of the second characteristic intensity (e.g., deep press intensity threshold (IT D )) in  FIG. 70  pops web browsing application back open (e.g., the device replaces display of the user interface  506  for user interface selection mode with user interface  502  for web browsing application). Thus, the user has toggled back to the originally displayed user interface. 
       FIGS. 8A-8R  illustrate exemplary user interfaces for navigating between user interfaces in accordance with some embodiments. The user interfaces in these figures are used to illustrate the processes described below, including the processes in  FIGS. 10A-10H, 11A-11E, 12A-12E, 13A-13D, 14A-14C, 15, 24A-24F, and 25A-25H . Although some of the examples which follow will be given with reference to inputs on a touch-screen display (where the touch-sensitive surface and the display are combined), in some embodiments, the device detects inputs on a touch-sensitive surface  451  that is separate from the display  450 , as shown in  FIG. 4B . 
       FIGS. 8A-8R  illustrate exemplary embodiments for navigating between multiple user interfaces represented in a user interface selection mode, including the ability to “peek” at and “pop” applications (e.g., and associated user interfaces) from a display of multiple user interface representations with user inputs detected on a touch-sensitive surface (e.g., a touch-sensitive display or touch-sensitive track pad separate from the display) in accordance with some embodiments. 
       FIGS. 8A-8D  illustrate an embodiment where a user “pops” (e.g., selects) a user interface for display on the device with a high intensity user input (e.g., a deep press).  FIG. 8A  illustrates display of user interface  506  for a user interface selection mode, including representation  508  of web browsing user interface  502  (“web browsing card  508 ”), representation  510  of messaging user interface  507  (“messaging card  510 ”), and representation  526  of photo management user interface  524  (“photo card  526 ”) of user interfaces that were previously displayed on the device. The user interface representations are displayed in a stack of cards, extending to the right from the base of the stack. Each card is ordered in a z-layer (e.g., substantially orthogonal to the plane of touch screen  112 , and is laterally offset to the right of the card below it, revealing a portion of each card. 
     Device  100  detects an increase in the intensity of contact  802  at a location corresponding to display of messaging card  510  from  FIG. 5A  to  FIG. 5A . In response, the displayed area of messaging card  510  increases (e.g., the user is peeking at messaging card  510 ) by moving web browsing card  508  further to the right (e.g., from location  508 -a in  FIG. 8A  to location  508 -b in  FIG. 8B ). 
     As illustrated in  FIG. 8C , display of the relative lateral positions of the cards is dynamically linked to the amount of pressure detected for the user contact. For example, in response to detecting a small decrease in the pressure of contact  802  from  FIG. 8B  to  FIG. 8C , web browsing card  508  starts to move back over messaging card  510  (e.g., web browsing card  508  moves from position  508 -b in  FIG. 8B  to position  508 -c in  FIG. 8C . In some embodiments, an animation is displayed to show movement of the user interface representations relative to one another in a manner that dynamically responds to small changes in the intensity of a contact. 
     Device  100  then detects a further increase in the pressure of contact  802 , exceeding a characteristic intensity (e.g., a deep press intensity threshold (IT D )). In response, messaging card  510  is “popped” out of the stack and the device opens the associated application (e.g., replaces display of user interface  506  for the user interface selection mode with display of user interface  507  for the messaging application). 
       FIGS. 8E-8F  illustrate an embodiment where “popping” of the card (e.g., selection of an application and corresponding user interface) includes an animation.  FIG. 8E  illustrates that messaging card is selected (e.g., “popped”) in response to detecting an increase in the pressure of contact  802 , exceeding a characteristic intensity (e.g., a deep press intensity threshold (IT D )). In response, device  100  displays an animation that transitions from display of user interface  506  for the user interface selection mode to display of user interface  507  for the messaging application. The animation includes sliding web browsing card  508  completely off of messaging card  510  (e.g., by moving we browsing card further to the right to position  508 -d). The animation also includes lifting messaging card  510  out of the stack, and gradually increasing the size of messaging card  510 , e.g., until display of user interface  507  fills the entirety of touch screen  112  (e.g., as illustrated by movement of messaging card from location  510 -b in  FIG. 8E  to location  510 -c in  FIG. 8F  to provide an effect that the card is moving towards the user in a virtual z-dimension. 
       FIGS. 8G-8H  illustrate an alternate embodiment for “peeking” at a user interface representation card.  FIG. 8G  illustrates display of a stack of user interface cards, as described for  FIG. 8A  (e.g., where web browsing card  508  is displayed on top of, and offset to the right of messaging card  510 , which is displayed on top of and offset to the right of photo card  526 ).  FIG. 8G  also illustrates contact  804  at a location of touch screen  112  corresponding to display of messaging card  510 . 
       FIG. 8H  illustrates that, in response to detecting an increase in the intensity of contact  804  when displayed over messaging card  510 , more area of messaging card is revealed. However, rather than sliding web browsing card  508  off of messaging card  510  to the right,  FIG. 8H  illustrates that messaging card  510  is moved to the left (e.g., messaging card moves from location  510 -a in  FIG. 8G  to location  510  in  FIG. 8H ), as if being taken out of the deck of cards. Thus,  FIGS. 8G and 8H  illustrate using the intensity of a contact (e.g.,  804 ) to reveal more of a user interface representation card in a stack by sliding the card out the stack in a direction opposite the direction in which the stack spreads away from the base of the stack. 
       FIG. 8I  illustrates another alternate embodiment for “peeking” at messaging card  510 , where, in response to detecting an increase in the intensity of contact  804  displayed at a location corresponding to display of messaging card  510 , web browsing card  508  moves off of messaging card  510  to the right, and messaging card  510  is pulled out of the deck to the left. Thus,  FIGS. 8G and 8I  illustrate using the intensity of a contact (e.g.,  804 ) to reveal more of a respective user interface representation card in a stack by both sliding the card out the stack in a direction opposite the direction in which the stack spreads away from the base of the stack, and sliding at least the card displayed direction over the respective user interface representation card further in the direction in which the stack spreads away from the base of the stack. 
       FIGS. 8J-8R  illustrate extended “peek” and “pop” navigation, where multiple cards are peeked at prior to popping open an application.  FIG. 8J  illustrates display of a graphical user interface  502  for a web browsing application on the electronic device.  FIG. 8K  illustrates that the device enters a user interface selection mode upon detection of a user input including contact  806  adjacent to the left edge of touch screen  112  (e.g., on the bezel) with a characteristic intensity (e.g., an intensity exceeding deep press intensity threshold (IT D ); e.g., an exemplary predetermined input). In response to activating user interface selection mode, device  100  replaces display of web browsing user interface  502  with user interface  506  for the user interface selection mode, as illustrated in  FIG. 8K . 
       FIG. 8K  illustrates display of a stack of user interface cards, as described for  FIG. 8A  (e.g., where web browsing card  508  is displayed on top of, and offset to the right of messaging card  510 , which is displayed on top of and offset to the right of photo card  526 ).  FIG. 8K  also illustrates contact  806  at a position  806 -a corresponding to the left edge of touch screen  112 , and having an intensity exceeding deep press intensity threshold (IT D ). 
     As illustrated in  FIG. 8L , device  100  detects a decrease in the intensity of user contact  806  below the deep press intensity threshold (IT D ). Device  100  also detects movement  808  of contact  806  from the left edge of the display (e.g., position  806 -a in  FIG. 8K ) to a location corresponding to display of messaging card  510 . 
       FIG. 8M  illustrates detection of an increase in intensity of user contact  806  when displayed over messaging card  510 , resulting in “peeking” of messaging card  510  via movement of web browsing card away from messaging card  510 . 
       FIG. 8N  illustrates detection of a decrease in the intensity of user contact  806 . In response, web browsing card  508  moves back over messaging card  510 . The device also detects continuation of movement  808  of contact  806  from location  806 -b in  FIG. 8N  to location  806 -c in  FIG. 8O , corresponding to display of photo card  526 . 
       FIG. 8P  illustrates detection of an increase in the intensity of contact  506  when displayed over photo card  526 , and in response, peeking of photo card  526  by moving display of web browsing card  508  and messaging card  510  to the right. 
       FIG. 8Q  illustrates detection of a further increase in the intensity of contact  806  in excess of a predefined threshold intensity (e.g., deep press intensity threshold (IT D )) when displayed over photo card  526 . In response, the contact “pops” photo card  526 , as illustrated by moving web browsing card  508  and messaging card  510  completely off of photo card  526 . Photo card  526  then expands (e.g., via a dynamic animation, to fill the entirety of touch screen  112  with user interface  524 , as electronic device enters the photo management application in  FIG. 8R . 
       FIGS. 9A-9H  illustrate exemplary user interfaces for navigating between user interfaces in accordance with some embodiments. The user interfaces in these figures are used to illustrate the processes described below, including the processes in  FIGS. 10A-10H ,  11 A- 11 E,  12 A- 12 E,  13 A- 13 D,  14 A- 14 C,  15 ,  24 A- 24 F, and  25 A- 25 H. Although some of the examples which follow will be given with reference to inputs on a touch-screen display (where the touch-sensitive surface and the display are combined), in some embodiments, the device detects inputs on a touch-sensitive surface  451  that is separate from the display  450 , as shown in  FIG. 4B . 
       FIG. 9A  illustrates display of user interface  506  for a user interface selection mode, including display of a stack of user interface representations (e.g., user interface representation cards  508 ,  510 , and  526  for web browsing user interface  502 , messaging user interface  507 , and image management user interface  524 ). As described for  FIGS. 5A-5HH , the user interface representation cards are spread out to the right from the base of the stack, and are ordered in Z-positions relative to one another (e.g., representation  508  is laterally offset to the right of representation  510  and is ordered above representation  510  along a Z-axis). 
     Device  100  detects a user input including contact  902  at a position on touch screen  112  that corresponds to display of user interface representation  526 . Contact  902  has a characteristic intensity below a predefined intensity threshold (e.g., below deep press intensity threshold (IT D )). In response to detecting contact  902  at a position corresponding with display of photo card  526 , device  100  reveals more of photo card  526  by moving messaging card  510  and web browsing card  508  to the right (e.g., away from photo card  526 ) from locations  510 -a and  508 -a in  FIG. 9A  to locations  510 -b and  508 -b in  FIG. 9B . Device  100  then detects movement of contact  902  from over photo card  526  to over messaging card  510  (e.g., from location  902 -a in  FIG. 9B  to location  902 -b in  FIG. 9C ). 
     As illustrated in  FIGS. 9C-9D , in response to contact  902  moving to a location corresponding to display of messaging card  510 , device  100  reveals more of messaging card  510  by moving messaging card  510  out from under web browsing card  508  and back towards the stack (e.g., to the left on display  112 ) from location  510 -b in  FIG. 9C  to location  510 -c in  FIG. 9D . 
       FIGS. 9E-9F  illustrate an embodiment where an application is selected from the user interface selection mode by lifting off a contact displayed at a location over a user interface representation card associated with that application. Device  100  detects lift off of contact  902  when positioned over messaging card  510  (e.g., termination of the user input including contact  902  at a position corresponding to display of card  510  on touch screen  112 ), selecting the messaging application associated with messaging card  510 . In response, device  100  replaces display of user interface  506  with display of user interface  507 , corresponding to user interface representation card  510 . E.g., device  100  opens the messaging application associated with user interface  507  because contact  902  was over the corresponding card when the user lifted off the contact. 
       FIGS. 9G-9H  illustrate an alternate embodiment where an application is selected from the user interface selection mode by “popping” it with a deep press gesture. Continuing from  FIGS. 9A-9D , Device  100  detects an increase in the intensity of contact  902  in excess of a predefined intensity threshold (e.g., deep press intensity threshold (IT D )) when contact  902  is positioned over messaging card  510 . In response, device  100  replaces display of user interface  506  with display of user interface  507 , corresponding to user interface representation card  510 . E.g., device  100  opens the messaging application associated with user interface  507  because contact  902  was over the corresponding card when the deep press was detected. 
       FIGS. 22A-22BA  illustrate exemplary user interfaces for performing operations independent of an application (e.g., system-wide actions), such as navigating between user interfaces in accordance with some embodiments. In some embodiments, this is achieved by a user interface that distinguishes at least two types of inputs originating from the edge of the touch screen, and in response performs a system-wide operation when a first type of input is detected and an application-specific application when the second type of input is detected. In some embodiments, the two types of inputs are distinguished based on at least their proximity to the edge of the touch-sensitive surface and a characteristic intensity of a contact included in the input. 
     The user interfaces in these figures are used to illustrate the processes described below, including the processes in  FIGS. 10A-10H, 11A-11E, 12A-12E, 13A-13D, 14A-14C, 15, 24A-24F, and 25A-25H . Although some of the examples which follow will be given with reference to inputs on a touch-screen display (where the touch-sensitive surface and the display are combined), in some embodiments, the device detects inputs on a touch-sensitive surface  451  that is separate from the display  450 , as shown in  FIG. 4B . 
       FIGS. 22A-22D  illustrate an embodiment where the device detects two inputs meeting system-gesture intensity criteria and determines whether to perform an application-specific action or a system-wide action based on the proximity of the input to the edge of the touch screen, in accordance with some embodiments.  FIG. 22A  illustrates a web browsing user interface  502  having two location boundaries,  2202  and  2204 . Location boundary  2202  defines an area of touch screen  112  (e.g., which extends to the left off of the touch screen) left of the boundary in which a contact must be detected in order to activate a system-wide action (e.g., when the contact also meets an intensity criteria), such as entering a user interface selection mode. Location boundary  2204  defines a larger area of touch screen  112  (e.g., which extends to the left off of the touch screen) left of the boundary in which a contact must be detected in order to activate a system-specific action (e.g., when the contact also meets an intensity criteria), such as navigating to a previous user interface displayed within the active application. 
     In  FIG. 22B , the device detects contact  2206  having a characteristic intensity above a threshold intensity required for performance of the system-wide action (e.g., intensity threshold IT L ). Contact  2206  also satisfies system-wide action positional criteria because it is detected to the left of boundary  2202 . Thus, although the contact also satisfies application-specific action criteria, in response to detecting movement of the contact to the right, the device enters a user interface selection mode, as indicated by replacement of web browsing user interface  502  with multitasking user interface  506  in  FIG. 22C . 
     In  FIG. 22D , the device detects contact  2212  having a characteristic intensity above a threshold intensity required for performance of the system-wide action (e.g., intensity threshold IT L ) and the application-specific action. However, contact  2212  does not satisfy system-wide action positional criteria because it is detected to the right of boundary  2202 . Because contact  2212  does satisfy application-specific positional criteria, in response to detecting movement of the contact to the right, the device navigates to a previously viewed user interface within the web browsing application, as indicated by replacement of web browsing user interface  502  with web browsing user interface  616  in  FIG. 22E . 
       FIGS. 22F-22G  illustrate an embodiment where the device adjusts the positional criteria required to perform a system-wide action in response to the shape of the contact detected. In  FIG. 22F  the device detects contact  2214  having a characteristic intensity above a threshold intensity required for performance of the system-wide action (e.g., intensity threshold IT L ). However, contact  2214  does not satisfy the default system-wide action positional criteria because it is detected to the right of boundary  2202 . However, because the contact is wider and elongated (e.g., which indicative of the user stretching their thumb to reach the left side of the device), as compared to a typical finger-tip contact, the device adjusts the system-wide action positional criteria such that contacts detected left of boundary  2204  satisfy the positional criteria. Thus, in response to detecting movement of the contact to the right, the device enters a user interface selection mode, as indicated by replacement of web browsing user interface  502  with multitasking user interface  506  in  FIG. 22G . 
       FIGS. 22H-22I  illustrate an embodiment where the device detects a contact that meets system-wide action positional criteria, but not system-wide action intensity. In  FIG. 22H  the device detects contact  2218  satisfying the positional requirement for performance of the system-wide action (e.g., because it was detected to the left of boundary  2202 . However, contact  2218  has a characteristic intensity below a threshold intensity required for performance of the system-wide action (e.g., intensity threshold IT L ) criteria. Because contact  2218  does satisfy application-specific intensity criteria, in response to detecting movement of the contact to the right, the device navigates to a previously viewed user interface within the web browsing application, as indicated by replacement of web browsing user interface  502  with web browsing user interface  616  in  FIG. 221 . 
       FIGS. 22J-22N  illustrate an embodiment where the boundary defining the system-wide action positional criteria is located off of the left edge of touch screen  112 .  FIG. 22J  illustrates a web browsing user interface  502  having location boundaries,  2222  and  2224  defining the right edge of positional requirements for performance of system-wide and application-specific actions. 
     In  FIG. 22K , the device detects contact  2226  having a characteristic intensity above a threshold intensity required for performance of the system-wide action (e.g., intensity threshold IT L ). Because the device determines that the user&#39;s digit used to make contact  2226  must extend to the left, off of touch screen  112  (e.g., based on the shape and size of the contact), the device projects (e.g., virtually) where the contact would extend to if the touch screen was wider, as indicated by the dashed lines in  FIG. 22K . Because the farthest point in the projected contact is left of positional boundary  2222 , contact  2226  also satisfies system-wide action positional criteria. Thus, in response to detecting movement of the contact to the right, the device enters a user interface selection mode, as indicated by replacement of web browsing user interface  502  with multitasking user interface  506  in  FIG. 22L . 
     In  FIG. 22M , the device detects contact  2230  having a characteristic intensity above a threshold intensity required for performance of the system-wide action (e.g., intensity threshold IT L ). The device then projects the left-most boundary of where contact  2230  would be located off of the edge of touch screen  112 . Because the farthest point in the projected contact is right of positional boundary  2222 , contact  2226  does not satisfy system-wide action positional criteria. Because contact  2230  does satisfy application-specific positional criteria, in response to detecting movement of the contact to the right, the device navigates to a previously viewed user interface within the web browsing application, as indicated by replacement of web browsing user interface  502  with web browsing user interface  616  in  FIG. 22N . 
       FIGS. 22O-22R  illustrate an embodiment where the device does not extend the system-wide action positional boundary in response to detecting a larger contact, when the contact is detected in the upper or lower corners of touch screen  112 . Thus, when the device detects a wider contact in  FIG. 22P  that would satisfy the modified positional criteria, the device performs the application-specific action, rather than the system-wide action, as illustrated in  FIG. 22R . 
       FIGS. 22S-22AA  illustrate an embodiment where the device modifies the system-wide action positional boundaries when the contact is travelling faster on the touch screen, to allow a further buffer for user&#39;s who are rushing the gesture. When the gesture meets speed criteria and intensity criteria within buffer zone  250 , the device still performs the system-wide action, as illustrated in  FIGS. 22S-22U . Where the gesture does not meet all three criteria simultaneously, the device does not perform the system-wide action, as illustrated in  FIGS. 22V-22X and 22Y-22AA . 
       FIGS. 22AB-22AG  illustrate an embodiment where the gesture also includes a directional criteria. When the gesture meets the directional criteria, as illustrated in  FIGS. 22AB-22AD , the device performs the system-wide action. When the gesture does not meet the direction criteria, as illustrated in  FIGS. 22AE-22AG , the device does not perform the system-wide action. 
       FIGS. 22AH-22AO  illustrate an embodiment where the system-wide action is still performed when the device first detects the input outside of the position boundary, but the contact is moved into the position boundary and then the intensity criteria is met, as illustrated in  FIGS. 22AH-22AK , but not in  FIGS. 22AL-22AO . 
       FIGS. 22AP-22AS  illustrate an embodiment where the device locks out the system-wide action if the input is ever detected at a location outside of buffer zone  2286 . 
       FIGS. 22AT-22AY  illustrate an embodiment where the system-wide action intensity criteria is higher during a time period immediately following detection of the contact on the screen. Where the contact moves outside of the activation zone prior to achieving the higher intensity requirement, the device does not perform the system-wide action, as illustrated in  FIGS. 22AT-22AU . Where the contact achieves the higher intensity requirement, or waits for the intensity threshold to drop, prior to moving outside of the activation zone, the device performs the system-wide action, as illustrated in  FIGS. 22AW-22AY . 
       FIGS. 22AZ-22BA  illustrate an embodiment where the system-wide action intensity criteria is higher near the top and bottom the of touch screen. 
       FIGS. 23A-23AT  illustrate exemplary user interfaces for performing operations independent of an application (e.g., system-wide actions), such as navigating between user interfaces in accordance with some embodiments. In some embodiments, this is achieved by distinguishing how far a contact meeting activation criteria (e.g., as described with respect to method  2400  and  FIGS. 22A-22BA  above) travels across the touch screen. 
     The user interfaces in these figures are used to illustrate the processes described below, including the processes in  FIGS. 10A-10H, 11A-11E, 12A-12E, 13A-13D, 14A-14C, 15, 24A-24F, and 25A-25H . Although some of the examples which follow will be given with reference to inputs on a touch-screen display (where the touch-sensitive surface and the display are combined), in some embodiments, the device detects inputs on a touch-sensitive surface  451  that is separate from the display  450 , as shown in  FIG. 4B . 
       FIG. 23A  illustrates a web browsing user interface  502  with positional boundaries  2302  and  2312 . When a contact meeting system-wide action activation criteria does not cross boundary  2302 , the device does not navigate to a new user interface upon termination of the input, as illustrated in  FIGS. 23B-23D . When a contact meeting system-wide action activation criteria crosses boundary  2302 , but not boundary  2312 , the device navigates to a user interface selection mode, as illustrated in  FIGS. 23E-23G . When a contact meeting system-wide action activation criteria crosses boundary  2302  and boundary  2312 , the device navigates to the last user interface active on the device, as illustrated in  FIGS. 23I-23K . 
       FIGS. 23L-23R  illustrate an embodiment where the device provides visual feedback as the user approaches and crosses over positional boundaries  2302  and  2312 . The feedback is dynamic and is reversed when the contact moves in the opposite direction on the touch screen. 
       FIGS. 23Q-23T  illustrate an embodiment where the device provides a hint that the intensity of a contact is approaching the intensity threshold required to activate the system-wide action. For example, as the intensity of contact  2326  approaches intensity threshold IT L , the device starts to slide active user interface  502  over to the right, revealing previously active user interface  507 . In response to detecting further increase in the intensity of contact  2326  above intensity threshold  2326  in  FIG. 23S , the device activates the system-wide action, allowing navigation between user interfaces (e.g., by sliding the contact into one of the three zones to the right. In response to detecting even further increase in the intensity of contact  2326  above deep press intensity threshold IT D  in  FIG. 23T , the device enters multitasking user interface selection mode, as indicated by replacement of web browsing user interface  502  with multitasking user interface  506  in  FIG. 23Y . 
       FIGS. 10A-10H  illustrate a flow diagram of a method  1000  of navigating between user interfaces in accordance with some embodiments. The method  1000  is performed at an electronic device (e.g., device  300 ,  FIG. 3 , or portable multifunction device  100 ,  FIG. 1A ) with a display and a touch-sensitive surface. In some embodiments, the display is a touch-screen display and the touch-sensitive surface is on or integrated with the display. In some embodiments, the display is separate from the touch-sensitive surface. In some embodiments, the touch-sensitive surface is part of a track pad or a remote control device that is separate from the display. In some embodiments, the operations in method  1000  are performed by an electronic device configured for management, playback, and/or streaming (e.g., from an external server) of audio and/or visual files that is in communication with a remote control and a display (e.g., Apple TV from Apple Inc. of Cupertino, Calif.). Some operations in method  1000  are, optionally, combined and/or the order of some operations is, optionally, changed. 
     As described below, the method  1000  provides an intuitive way to navigate between user interfaces. The method reduces the number, extent, and/or nature of the inputs from a user when navigating between user interfaces, thereby creating a more efficient human-machine interface. For battery-operated electronic devices, enabling a user to navigate between user interfaces faster and more efficiently conserves power and increases the time between battery charges. 
     In some embodiments, the device displays ( 1002 ) a first user interface on the display. For example, a user interface of an open application (e.g., user interface  502  for a web browsing application in  FIGS. 5A-5B, 6A-6B, 6D, 6M, 60, 6S-6T, 7A-7B, and 70 , user interface  616  for a web browsing application in  FIG. 6P and 6U , user interface  507  for a messaging application in  FIGS. 5CC, 6Q, 7F, 7J-7L, 8D, 8J, 9F, and 9H , or user interface  526  for image management application in  FIG. 8R ). The first user interface corresponds to a first user interface representation in a plurality of user interface representations. For example, as described further below, the user interface representations correspond to, in certain embodiments, user interfaces of open applications, current and previously viewed user interfaces of a single application (e.g., open user interfaces for a web browsing application, each displaying a same or different web site, or a history of previously viewed user interfaces for a web browsing application—e.g., corresponding to at least a partial browser history), messages in an e-mail chain, menu options in a menu hierarchy (e.g., a selection of files, such as audio and/or visual files for playback or streaming), etc. 
     While displaying the first user interface, the device detects ( 1004 ) a predetermined input. For example, a double-tap or double press on the “home” button on the device; or, for an electronic device that includes one or more sensors to detect intensity of contacts with a touch-sensitive display, a deep press on a predetermined area of the first user interface (e.g., an upper left corner); a deep press with the flat portion of a thumb anywhere on the first user interface; or a deep press on a predetermined area of the device, such as on the left edge of the touch-sensitive surface (e.g., a touch-sensitive display or touch-sensitive track pad separate from the display), in a predefined area adjacent to an edge (e.g., the left edge) of the touch-sensitive surface (e.g., touch-sensitive display). For example, a deep press on the bezel or a predetermined area of the bezel, such as the bezel adjacent to the left edge of the touch-sensitive surface (e.g., deep press  504  in  FIG. 504, 608  in  FIG. 6H, 612  in  FIG. 6M, and 806  in  FIG. 8K ). 
     In response ( 1005 ) to detecting the predetermined input: the device enters ( 1006 ) a user interface selection mode, and displays ( 1008 ) a plurality of user interface representations in a stack with at least a portion of a first user interface representation visible and at least a portion of a second user interface representation visible. For example, in response to detecting deep press  504  in  FIG. 5B , multifunction device  100  displays user interface representations  508  (corresponding to user interface  502  of a web browsing application, which was displayed on the screen when the initiating input was detected) and  510  (corresponding to user interface  507  of a messaging application) in  FIGS. 5C and 5D . 
     In some embodiments, a representation of the user interface that was displayed on the screen immediately preceding entry into the user interface selection mode is displayed on the top of the stack, or as the first representation corresponding to an open application (e.g., when one or more representations of a home screen or transient application is also displayed upon entry of the user interface selection mode. For example, in  FIG. 5C , user interface representation  508  (corresponding to user interface  502 , which was displayed at the time deep press  504  was detected) is displayed above user interface representation  507  in the stack. 
     In some embodiments, a representation of the user interface that was displayed on the screen immediately preceding entry into the user interface selection mode is displayed below at least a second user interface representation (e.g., a representation for the user interface that was displayed immediately preceding display of the user interface that was displayed when the user interface selection mode was initiated). For example, in  FIG. 5D , user interface representation  508  (corresponding to user interface  502 , which was displayed at the time deep press  504  was detected) is displayed below user interface representation  507  in the stack. 
     In some embodiments, the device displays a second user interface on the display, where the second user interface corresponds to the second user interface representation of the plurality of user interface presentations (e.g., the representation of the user interface displayed when the user interface selection mode was initiated is displayed as the second representation in the stack, as illustrated in  FIG. 5D ). While displaying the second user interface, the device detects a predetermined input. In response to detecting the predetermined input: the device enters the user interface selection mode and displays the stack with at least a portion of the first user interface representation visible and at least a portion of the second user interface representation visible. 
     In some embodiments, in response to detecting the predetermined input for entering the user interface selection mode, at least a portion of a third user interface representation is visibly displayed. For example, in response to detecting deep press  504  in  FIG. 5B , multifunction device  100  displays user interface representations  508 ,  510 , and  526  (corresponding to user interface  524  of an image management application) in  FIGS. 5E and 5F . 
     In some embodiments, the rest of the representations in the stack are either off-screen or are beneath the first, second, and optional third representations, which include visible information. For example,  FIG. 5E  illustrates indication  503  (e.g., an image of representation edges or actual edges of additional user interface representations) beneath third user interface representation  526  in  FIGS. 5E and 5F . 
     In some embodiments, in response ( 1005 ) to detecting the predetermined input: the device ceases to display ( 1010 ) a status bar on the display. The status bar is displayed concurrently with a respective user interface prior to entering the user interface selection mode and displaying the stack. For example, status bar  503  is displayed on user interface  502  in  FIG. 5A  prior to the device entering the user interface selection mode. Upon detecting deep press  504  in  FIG. 5B , the device enters the user interface selection mode (e.g., as indicated by display of the stack in  FIG. 5E ), which does not include display of status bar  503  in corresponding user interface  506 , as illustrated in  FIG. 5E . In some embodiments, as illustrated in  FIG. 5C , the user interface for the user interface selection mode (e.g., user interface  506 ) includes display of a status bar (e.g., status bar  503 ). 
     In some embodiments, the status bar includes the current time, battery level, cellular signal strength indicator, WiFi signal strength indicator, etc. The status bar is usually displayed at all times with the user interface of an open application. In some embodiments, removal of the status bar provides an indication to a user that the stack in the user interface selection mode is not a regular user interface of an application, but a system user interface configured for navigation, selection, and management (e.g., closing) of the open applications on the device. In some embodiments, haptic feedback is provided when the user interface selection mode is entered. 
     Method  1000  includes that the device (e.g., multifunction device  100 ) displays ( 1012 ) a plurality of user interface representations in a stack on the display. In some embodiments, the plurality of user interface representations resemble a stack of cards (or other objects) in a z-layer order (e.g., positioned relative to each other along a z-axis substantially orthogonal to the plane of the display on the device to provide the effect that the cards are stacked one on top of another) that represent user interfaces of open applications, cards that represent current and previously viewed user interfaces of a single application, cards that represent messages in an e-mail chain, cards that represent different menu options in a menu hierarchy, etc. For example,  FIGS. 5E and 5F  illustrate a stack including representations  508 ,  510 , and  526  of user interfaces of open applications. Representation  508  is displayed as the top card, representation  510  as the middle card, and representation  526  as the bottom card in a z-layer order. In some embodiments, the stack is displayed as a substantially two-dimensional representation (although still with a z-layer order of cards in some embodiments), for example, as illustrated in  FIG. 5E . In some embodiments, the stack is displayed as a substantially three-dimensional representation, for example, as illustrated in  FIG. 5F . 
     At least a first user interface representation (e.g., a card representing the application that was being displayed immediately prior to displaying the stack in a user interface selection mode, such as a mode for selecting among open applications, a mode for selecting among user interfaces in a single open application, or a mode for selecting from among menu items in a menu (e.g., a menu in a menu hierarchy for a set-top box, etc.)) and a second user interface representation (e.g., a card representing another open application, a transient application, or a home screen or application springboard) disposed above the first user interface representation in the stack are visible on the display. For example, first user interface representation  510  is displayed as below second user interface representation  508  in  FIGS. 5E-5F . 
     The second user interface representation is offset from the first user interface representation in a first direction (e.g., laterally offset to the right on the display). For example, second user interface  508  is offset to the right of the center of first user interface representation  510  in  FIG. 5E-5F . 
     The second user interface representation partially exposes the first user interface representation. In some embodiments, representations in the stack are partially spread out in one direction on the display (e.g., to the right, as shown in  FIGS. 5E-5F ). In some embodiments, at a given time, information (e.g., an icon, title, and content for the corresponding user interface) for a predetermined number of the representations (e.g., 2, 3, 4, or 5 representations) in the stack is visible, while the rest of the representations in the stack are either off-screen or are beneath the representations that include visible information. In some embodiments, the representations that are beneath the representations that include visible information are stacked together so closely that no information is displayed for these representations. In some embodiments, the representations that are beneath the representations that include visible information are stylistic representations, such as just generic edges  503  of these representations, as shown in  FIGS. 5E-5F . 
     In some embodiments, a respective user interface representation has a corresponding position in the stack ( 1014 ). For example, user interface representation  508  has a corresponding first position in the stack, user interface representation  510  has a corresponding second position in the stack, and user interface representation  526  has a corresponding third position in the stack, as illustrated in  FIG. 5P . 
     In some embodiments, for a respective user interface representation that is visible on the display: the device determines ( 1016 ) a respective relative z-position of the user interface representation as compared to one or more other user interface representations that are concurrently visible on the display; and applies ( 1018 ) a level of blurring to the user interface representation in accordance with the relative z-position (e.g., relative height in the z-dimension, or relative z-layer level in the stack) of the user interface representation as compared to the one or more other user interface representations that are concurrently visible on the display. 
     For example, in some embodiments, upon entering an application selection mode, the stack of user interface representations represent a stack of open applications, the lower lying user interface representations correspond to open applications that have not been viewed for longer periods of time, and more blurring is applied to the user interface representations for those applications than to the user interface representations of the more recently viewed open applications. In some embodiments, the user interface representation for the most recently viewed application is not blurred; the user interface representation for the next most recently viewed application is blurred by a first amount; user interface representations for still earlier open applications are blurred by a second amount that is greater than the first amount; and so on. For example, as illustrated in  FIG. 5P , device  100  applies little or no blurring to user interface representation  508  because the card has a first relative z-position on top of the cards concurrently visible on touch screen  112 . Device  100  applies moderate blurring to user interface representation  510  because the card has a second relative z-position in the middle of the cards concurrently visible on touch screen  112 . Device  100  applies substantial blurring to user interface representation  526  because the card has a third relative z-position at the bottom of the cards concurrently visible on touch screen  112 . 
     In some embodiments, a respective user interface representation has a corresponding simulated absolute z-position in the stack. For a user interface representation that is visible on the display, the device applies ( 1020 ) a level of blurring to the user interface representation in accordance with the corresponding simulated absolute z-position of the user interface representation in a z-dimension. 
     For example, in some embodiments, the z-dimension is the dimension that is perpendicular (e.g., substantially orthogonal) to the plane of the display, or the lateral directions of the space represented on the display. In some embodiments, the level of blurring applied to each of the user interface representations visible on the display is determined based on the simulated absolute z-position of the user interface representation. In some embodiments, the variation in the level of blurring applied to each user interface representation is gradual and directly correlated to the current simulated absolute z-position of the user interface representation. In some embodiments, the stack of user interface representations move on a concave down increasing x-z curve in the x-direction, and the gap between each pair of adjacent user interface representations in the z-direction is maintained at a constant value during the movement of the user interface representations along the x-z curve in the x-direction. 
     In some embodiments, a respective user interface representation is associated with a respective title area (e.g., a title bar, such as title bar  512  associated with user interface representation  508  in  FIG. 5C  and title bar  520  associated with user interface representation  510  in  FIG. 5D ) with respective title content (e.g., the title area includes an icon (e.g., icon  516  in  FIG. 5C  and icon  518  in  FIG. 5D ) and a name of the application (or web page, menu, etc., such as “Safari”  514  in  FIG. 5C  and “Messages”  520  in  FIG. 5D ) represented by the user interface representation). In some embodiments, for a user interface representation currently visible below an adjacent user interface representation on the display, the device applies ( 1022 ) a visual effect (e.g., blurring, fading, and/or clipping, as shown in  FIG. 5DD ) to at least a first portion (e.g., only the title text portion of the title content, e.g., fading of “Photo”  532  in  FIG. 5DD , or both the title text and the icon in the title content, e.g., fading of both “Photo”  532  and icon  528  in  FIG. 5DD ) of the title content of the user interface representation as the adjacent user interface representation approaches (e.g., as user interface representation  510  slides over user interface representation  526  in  FIG. 5DD ). 
     In some embodiments, the device applies ( 1024 ) the visual effect to title text in the title content while maintaining an original appearance of an icon in the title content, as the title area of an adjacent user interface representation or the adjacent user interface representation moves within a threshold lateral distance on the display of the title content. For example, “Photo”  532  fades away in  FIG. 5DD  as user interface representation  510  moves to location  510 -b, near “Photo”  532 , prior to icon  526  fading away). 
     In some embodiments, the stack includes ( 1026 ) user interface representations for a home screen (e.g., representations of any of one or more user interfaces accessible immediately after the startup of the device, such as a notification center, a search UI, or a springboard or dashboard showing applications available on the device, such as representation  554  of user interface  552  of a home screen in  FIG. 5Q ), zero or more transient application user interface representations (e.g., representations of a user interface for an incoming or ongoing telephone or IP call session (e.g., user interface representation  554  of user interface  556  for an incoming telephone call in  FIG. 5W ), a user interface showing a handoff of one or more application sessions from a different device, a user interface for recommending an application, a user interface for a printing session, etc.), and one or more open application user interface representations (e.g., representations of the current application being viewed just before entering the user interface selection mode, the prior application before the current application, and other earlier open applications, (e.g., user interface representations  508 ,  510 , and  526  in  FIGS. 5E-5F ). 
     As used in the specification and claims, the term “open application” refers to a software application with retained state information (e.g., as part of device/global internal state  157  and/or application internal state  192 ). An open application is any one of the following types of applications:
         an active application, which is currently displayed on display  112  (or a corresponding application view is currently displayed on the display);   a background application (or background process), which is not currently displayed on display  112 , but one or more application processes (e.g., instructions) for the corresponding application are being processed by one or more processors  120  (i.e., running);   a suspended application, which is not currently running, and the application is stored in a volatile memory (e.g., DRAM, SRAM, DDR RAM, or other volatile random access solid state memory device of memory  102 ); and   a hibernated application, which is not running, and the application is stored in a non-volatile memory (e.g., one or more magnetic disk storage devices, optical disk storage devices, flash memory devices, or other non-volatile solid state storage devices of memory  102 ).       

     As used herein, the term “closed application” refers to software applications without retained state information (e.g., state information for closed applications is not stored in a memory of the device). Accordingly, closing an application includes stopping and/or removing application processes for the application and removing state information for the application from the memory of the device. Generally, opening a second application while in a first application does not close the first application. When the second application is displayed and the first application ceases to be displayed, the first application, which was an active application when displayed, may become a background application, suspended application, or hibernated application, but the first application remains an open application while its state information is retained by the device. 
     In some embodiments, in z-layer order, the user interface representations for a home screen are displayed above the transient application user interface representations, which in turn are displayed above the open application user interface representations. As used herein, a “z-layer order” is the front-to-back order of displayed objects (e.g., user interface representations). Thus, if two objects overlap, the object that is higher in the layer order (e.g., the object that is “on top of,” “in front of,” or “above”) is displayed at any points where the two objects overlap, thereby partially obscuring the object that is lower in the layer order (e.g., the object that is “beneath,” “behind,” or “in back of” the other object). The “z-layer order” is sometimes also called the “layer order,” “z order,” or “front-to-back object order.” 
     In some embodiments, the transient application user interface representations include ( 1028 ) a telephony interface representation for an active call or a missed call, a continuity interface representation for a suggested application, a continuity interface representation for a hand-off from another device, and a printer interface representation for an active print job. 
     Method  1000  also includes that the device detects ( 1030 ) a first drag gesture by a first contact at a location on the touch-sensitive surface that corresponds to a location of the first user interface representation on the display (e.g., device  100  detects a drag gesture including contact  530  and movement  532  on touch screen  112  at a location corresponding to display of user interface representation  510  in  FIG. 5G ), the first contact moving across the touch-sensitive surface in a direction that corresponds to the first direction on the display (e.g., movement  532  of contact  530  moves across touch screen  112  from left to right in  FIGS. 5G-5I ). 
     While the first contact is at a location on the touch-sensitive surface that corresponds to the location of the first user interface representation on the display and moving across the touch-sensitive surface in a direction that corresponds to the first direction on the display ( 1032 ): the device moves ( 1034 ) the first user interface representation (e.g., user interface representation  510  in  FIGS. 5G and 5R ) in the first direction on the display at a first speed in accordance with a speed of the first contact on the touch-sensitive surface. For example, on a touch-sensitive display (e.g., touch screen  112 ), the card or other representation under the finger contact moves with the same speed as the finger contact (e.g., user interface representation  510  moves with the same speed as contact  530  in  FIGS. 5G-5I , and user interface representation  510  moves with the same speed as contact  556  in  FIGS. 5R-5 , as illustrated by the constant positional relationship between the display of the user interface representation and the contact on touch screen  112 ). On a display coupled to a track pad, the card or other representation at the location corresponding to the location of the contact moves at an onscreen speed that corresponds to (or is based on) the speed of the finger contact on the track pad. In some embodiments, a focus selector is shown on the display to indicate the onscreen location that corresponds to the location of the contact on the touch-sensitive surface. In some embodiments, the focus selector may be represented by a cursor, a movable icon, or visual differentiators that separates an onscreen object (e.g., a user interface representation) from its peers that do not have the focus. 
     While the first contact is at a location on the touch-sensitive surface that corresponds to the location of the first user interface representation on the display and moving across the touch-sensitive surface in a direction that corresponds to the first direction on the display ( 1032 ): the device also moves ( 1036 ) the second user interface representation (e.g., user interface representation  508  in  FIGS. 5G and 5R ), disposed above the first user interface representation, in the first direction at a second speed greater than the first speed. 
     In some embodiments, the first direction is rightward. In some embodiments, the first speed is the same speed as the current speed of the contact. In some embodiments, this movement of the first user interface representation creates a visual effect that the finger contact is grabbing and dragging the first user interface representation. At the same time, the second user interface representation is moving faster than the first user interface representation. This faster movement of the second user interface representation creates the visual effect that as the second user interface representation moves in the first direction towards the edge of the display, an increasingly larger portion of the first user interface representation is revealed from underneath the second user interface representation. For example, as second user interface representation  508  moves towards the right on the display with greater speed than does first user interface representation  510 , more of user interface representation  510  is revealed when displayed at location  510 -b than when displayed at location  510 -a, prior to the movement to the right, as illustrated in  FIGS. 5G-5H . In combination, these two concurrent movements enable a user to see more of the first user interface representation before deciding whether to select and display the corresponding first user interface. 
     In some embodiments, the stack includes at least a third user interface representation disposed below the first user interface representation (e.g., user interface representation  526  in  FIGS. 5E-5F ). The first user interface representation is offset from the third user interface representation in the first direction (e.g., user interface  510  is offset to the right of user interface representation  526  in  FIGS. 5E-5F ). The first user interface representation partially exposes the third user interface representation. While the first contact is at a location on the touch-sensitive interface that corresponds to the first user interface representation on the display and the first contact is moving across the touch-sensitive surface in a direction that corresponds to the first direction on the display: the device moves ( 1038 ) the third user interface representation, disposed below the first user interface representation, in the first direction at a third speed less than the first speed. 
     For example, the third user interface representation, below the first user interface representation (e.g., the card under the finger contact), moves at a slower speed than the first user interface representation, such that more of the third user interface representation is exposed as the finger contact moves across the touch-sensitive surface in a direction that corresponds to the first direction on the display. For example,  FIG. 5O  illustrates representative speeds of user interface representations  508  (e.g., second user interface representation),  510  (e.g., first user interface representation), and  526  (e.g., third user interface representation) relative to movement  532  of contact  530  in  FIGS. 5G-5I . 
     In some embodiments, at the same time, one or more user interface representations below the third user interface representation are revealed as the third user interface representation moves in the first direction (e.g., to the right). For example, user interface representations  534  and  540  are revealed as third user interface representation  526  moves to the right in response to detection of a user input including contact  530  and movement  532 , as shown in  FIGS. 5H-5I ). 
     In some embodiments, a difference between the second speed and the first speed maintains ( 1040 ) a first constant z-position difference between the second user interface representation and the first user interface representation. A difference between the first speed and the third speed maintains a second constant z-position difference between the first user interface representation and the third user interface representation. The first constant z-position difference is the same as the second z-position difference. In some embodiments, the cards travel on a concave down increasing x-z curve, where the z-spacing between adjacent cards is maintained as the cards move to along the x-direction. Because the slope of the curve decreases with increasing x positions, the cards move at higher and higher speeds in the x-direction as their current x-positions increase. 
     In some embodiments, a difference between the second speed and the first speed is equal to a difference between the first speed and the third speed ( 1042 ). 
     In some embodiments, a ratio between the second speed and the first speed is equal to a ratio between the first speed and the third speed ( 1044 ). 
     In some embodiments, while moving the third user interface representation disposed below the first user interface representation at the third speed ( 1046 ) in the first direction (e.g., moving user interface representation  526  to the right on touch screen  112  at a relative speed less than the speed user interface  510  is travelling to the right (e.g., as illustrated in  FIG. 5O ) in  FIGS. 5G-5I ): the device reveals ( 1048 ) an increasingly larger portion of a fourth user interface representation disposed below the third user interface representation in the stack on the display (e.g., user interface  534  is gradually revealed from behind user interface representation  526  in  FIGS. 5G-5I ). 
     In some embodiments, the device then moves ( 1050 ) the fourth user interface representation disposed below the third user interface representation at a fourth speed that is less than the third speed in the first direction. In some embodiments, one or more user interface representations disposed below the fourth user interface representation in the stack are revealed (e.g., user interface representation  540 , as in  FIGS. 5I and 5T ) in this manner too, as the higher-up user interface representations move in the first direction. 
     In some embodiments, after detecting the first drag gesture (e.g., drag gesture including contact  530  and movement  532  in  FIGS. 5G-5I ), the device detects ( 1052 ) a second drag gesture by a second contact on the touch-sensitive surface at a location that corresponds to the first user interface representation on the display, the second contact moving across the touch-sensitive surface in a direction that corresponds to a second direction on the display (e.g., leftward) opposite to the first direction on the display (e.g., rightward). For example, device  100  detects drag gesture including contact  546  and movement  548  originating from a location on the display corresponding to user interface representation  510 , and proceeding to the left, in  FIGS. 5L-5N . 
     In some embodiments, the second contact is the same as the first contact and the second drag gesture follows the first drag gesture, without an intervening lift off of the first contact. In some embodiments, the first contact lifts off after the first drag gesture and second drag gesture is made with a second contact after the second contact touches down on the touch-sensitive surface, as illustrated in the series of  FIGS. 5J ;  5 L- 5 N. 
     While the second contact is at a location on the touch-sensitive surface that corresponds the first user interface representation on the display and the second contact is moving ( 1054 ) across the touch-sensitive surface in a direction that corresponds to the second direction on the display opposite the first direction on the display: the device moves ( 1056 ) the first user interface representation (e.g., user interface representation  510  in  FIGS. 5L-5N ) in the second direction at a new first speed on the display in accordance with a speed of the second contact on the touch-sensitive surface (e.g., on a touch-sensitive display, the card or other representation under the finger contact moves with the same speed as the finger contact). The device also moves ( 1058 ) the second user interface representation (e.g., user interface representation  508  in  FIGS. 5L-5N ), disposed above the first user interface representation, in the second direction at a new second speed greater than the new first speed. The device also moves ( 560 ) the third user interface representation (e.g., user interface representation  526  in  FIGS. 5L-5N ), disposed below the first user interface representation, in the second direction at a new third speed less than the new first speed. 
     In some embodiments, while moving the second user interface representation in the second direction faster than moving the first user interface representation in the second direction, the device detects ( 1062 ) that the second user interface representation has moved in between the first user interface representation and a location on the display that corresponds to a location of the second contact on the touch-sensitive surface. For example, on a touch-sensitive display, detecting that a portion of the second contact or a representative point of the second contact (e.g., a centroid) is touching the second user interface representation, instead of touching the first user interface representation (e.g., the centroid of contact  546  is touching user interface representation  508 , rather than user interface representation  510 , at location  546 -f in  FIG. 5N ). 
     In response to detecting that the second user interface representation has moved in between the first user interface and a location on the display that corresponds to the location of the second contact on the touch-sensitive surface ( 1064 ): the device moves ( 1068 ) the second user interface representation in the second direction at a modified second speed in accordance with a current speed of the second contact. E.g., on a touch-sensitive display, the second user interface representation (e.g., user interface representation  508  in  FIG. 5N ) has caught up with the finger movement, and starts to move at the same speed as the second finger contact, instead of having the first user interface representation move at the same speed as the second finger contact in the second drag gesture (e.g., as illustrated by the change of the speed of user interface representation  508 , along speed curve  550 , upon reaching location  508 -f in  FIG. 5O ). 
     The device also moves ( 1070 ) the first user interface representation (e.g., user interface representation  510 ), disposed below the second user interface representation, in the second direction at a modified first speed less than the modified second speed. In some embodiments, on a touch-sensitive display, once the second user interface representation becomes the representation underneath the finger contact, the first user interface representation moves at a speed that is a slower than the speed of the second user interface representation (e.g., at a speed a fixed amount or a proportional amount below the speed of the second user interface representation, as illustrated on speed curve  550  in  FIG. 5O ). 
     In some embodiments, the device also moves ( 1072 ) the third user interface representation (e.g., user interface representation  526  in  FIG. 5N ), disposed below the first user interface representation, in the second direction at a modified third speed less than the modified first speed (e.g., as illustrated on speed curve  550  in  FIG. 5O ). 
     In some embodiments, a difference between the modified second speed and the modified first speed maintains ( 1074 ) a first constant z-position difference between the second user interface representation and the first user interface representation, while a difference between the modified first speed and the modified third speed maintains a second constant z-position difference between the first user interface representation and the third user interface representation, where the first constant z-position difference is the same as the second z-position difference. 
     In some embodiments, a difference between the modified second speed and the modified first speed is equal to a difference between the modified first speed and the modified third speed ( 1076 ). 
     In some embodiments, a ratio between the modified second speed and the modified first speed is equal to a ratio between the modified first speed and the modified third speed ( 1078 ). 
     In some embodiments, while displaying, in the stack, at least the first user interface representation and the second user interface representation above the first user interface representation, the device detects ( 1080 ) activation of a transient application at the device. For example, while displaying user interface representations  508 ,  510 ,  526 , and  534 , device  100  detects an incoming phone call, activating a telephony application, as illustrated in  FIGS. 5U-5V . 
     In response to detecting activation of the transient application, the device inserts ( 1082 ) a user interface representation for the transient application in the stack between the first user interface representation and the second user interface representation. For example, user interface representation  554  of user interface  556  corresponding to a telephony application is inserted between user interface representations  510  and  526  in  FIGS. 5U-5W . In some embodiments, to make room for the user interface representation of the transient application on the display, the second user interface representation is moved to the right, and the user interface representation of the transient application takes the former place of the second user interface representation (e.g., user interface representations  510  and  508  move to the right to make space for insertion of user representation  554  into the stack in  FIGS. 5V-5W ). 
     In some embodiments, while displaying, in the stack, at least the first user interface representation and the second user interface representation above the first user interface representation, the device detects ( 1084 ) a deletion input directed to the first user interface representation (e.g., an upward drag gesture at a location on the touch-sensitive surface that corresponds to a location on the first user interface representation). For example, device  100  detects the drag gesture including contact  560  and movement  562  at a location on touch screen  112  corresponding to display of user interface representation  510  in  FIG. 5X . 
     In response to detecting the deletion input directed to the first user interface representation ( 1086 ): the device removes ( 1088 ) the first user interface representation from a first position in the stack (e.g., user interface  510  is removed from the stack in  FIGS. 5X-5Z . The device also moves ( 1090 ) a respective user interface representation disposed immediately below the first user interface representation into the first position in the stack (e.g., user interface representation  526  is moved up in the stack to take the position vacated by user interface representation  510  in  FIGS. 5Z-5AA ). In some embodiments, the application corresponding to the first user interface representation is closed in response to detecting the deletion input directed to the first user interface representation. 
     In some embodiments, after detecting termination of the first drag gesture, the device displays ( 1091 ) at least two of the user interface representations in the stack on the display (e.g., user interface representations  508 ,  510 , and  526  in  FIG. 5BB ). While displaying at least two of the plurality of user interface representations in the stack, the device detects ( 1092 ) a selection input (e.g., a tap gesture at a location on the touch-sensitive surface that corresponds to a location on a user interface representation) directed to one of the at least two user interface representations in the stack. For example, device  100  detects the tap gesture including contact  564  at a location on touch screen  112  corresponding to display of user interface representation  510  in  FIG. 5BB . 
     In response to detecting the selection input ( 1093 ): the device ceases to display ( 1094 ) the stack, and displays ( 1095 ) a user interface that corresponds to the selected one of the at least two user interface representations. In some embodiments, the user interface that corresponds to the selected user interface representation is displayed without displaying any user interfaces that correspond to other user interface representations in the stack. In some embodiments, the display of the user interface that corresponds to the selected user interface representation replaces the display of the stack. For example, in response to detecting the tap gesture including contact  564  at a location on touch screen  112  corresponding to display of user interface representation  510  of user interface  507 , device  100  exits the user interface selection mode and displays user interface  507  on touch screen  112 . 
     In some embodiments, while at least the first user interface representation and the second user interface representation, disposed above the first user interface representation in the stack, are stationary on the display, the device detects ( 1096 ) a first flick gesture by a second contact at a location on the touch-sensitive surface that corresponds to one of the first user interface representation or the second user interface representation on the display. The flick gesture moves across the touch-sensitive surface in a direction that corresponds to the first direction on the display. For example, device  100  detects the flick gesture including contact  556  and movement  558  at a location on touch screen  112  that corresponds to display of user interface representation  510 . 
     In response to detecting the first flick gesture by the second contact, the device moves the second user interface representation with a simulated inertia that is based on whether the second contact was detected at a location on the touch-sensitive surface that corresponds to the first user interface representation or to the second user interface representation on the display (e.g., user interface representation  510  travels farther than the length of movement  558 ). In some embodiments, when the flick gesture is directed to the second user interface representation, the second user interface representation moves with a smaller inertia than if the flick gesture is directed to the first user interface representation. In some embodiments, when the flick gesture is directed to the second user interface representation, the second user interface representation moves with a larger inertia than if the flick gesture is directed to the first user interface representation. In some embodiments, if the top card is flicked to the right, that top card flies off of the screen faster than it would have if a lower laying card were flicked to the right, which would push the top card to the right indirectly. 
     It should be understood that the particular order in which the operations in  FIGS. 10AA-10H  have been described is merely exemplary and is not intended to indicate that the described order is the only order in which the operations could be performed. One of ordinary skill in the art would recognize various ways to reorder the operations described herein. Additionally, it should be noted that details of other processes described herein with respect to other methods described herein (e.g., methods  1100 ,  1200 ,  1300 ,  1400 ,  1500 ,  2400 , and  2500 ) are also applicable in an analogous manner to method  1000  described above with respect to  FIGS. 10A-10H . For example, the contacts, gestures, user interface objects, focus selectors, and animations described above with reference to method  1000  optionally have one or more of the characteristics of the contacts, gestures, user interface objects, focus selectors, and animations described herein with reference to other methods described herein (e.g., methods  1100 ,  1200 ,  1300 ,  1400 ,  1500 ,  2400 , and  2500 ). For brevity, these details are not repeated here. 
       FIGS. 11A-11E  illustrate a flow diagram of a method  1100  of navigating between user interfaces in accordance with some embodiments. The method  1100  is performed at an electronic device (e.g., device  300 ,  FIG. 3 , or portable multifunction device  100 ,  FIG. 1A ) with a display, a touch-sensitive surface, and one or more sensors to detect intensity of contacts with the touch-sensitive surface. In some embodiments, the display is a touch-screen display and the touch-sensitive surface is on or integrated with the display. In some embodiments, the display is separate from the touch-sensitive surface. In some embodiments, the touch-sensitive surface is part of a track pad or a remote control device that is separate from the display. In some embodiments, the operations in method  1000  are performed by an electronic device configured for management, playback, and/or streaming (e.g., from an external server) of audio and/or visual files that is in communication with a remote control and a display (e.g., Apple TV from Apple Inc. of Cupertino, Calif.). Some operations in method  1100  are, optionally, combined and/or the order of some operations is, optionally, changed. 
     As described below, the method  1100  provides an intuitive way to navigate between user interfaces. The method reduces the cognitive burden on a user when navigating between user interfaces, thereby creating a more efficient human-machine interface. For battery-operated electronic devices, enabling a user to navigate between user interfaces faster and more efficiently conserves power and increases the time between battery charges. 
     The device displays ( 1102 ) a first user interface on the display (e.g., user interface  502  in  FIG. 6A ). In some embodiments, the first user interface is the user interface of a currently open application. In some embodiments, the first user interface is the current user interface of an application, which is preceded by a sequence of previous user interfaces for the application that are accessible by a “back” button provided on the user interfaces for the application. 
     While displaying the first user interface on the display, the device detects ( 1104 ) an input by a first contact on the touch-sensitive surface (e.g., contact  602  in  FIG. 6B ). In some embodiments, the input by the first contact starts in a predefined location on a touch-sensitive display, such as on the left edge of the touch-sensitive display or in a predefined area adjacent to the left edge of the touch-sensitive display. In some embodiments, the input by the first contact starts at a location on the touch-sensitive surface that corresponds to a predefined location on a display, such as on the left edge of the display or in a predefined area adjacent to the left edge of the display. In some embodiments, the input includes a press input made with the flat portion of a thumb. 
     While detecting the input by the first contact, the device displays ( 1106 ) a first user interface representation and at least a second user interface representation on the display (e.g., user interface representations  508  and  510  in  FIG. 6C ). 
     In some embodiments, in accordance with a determination that the first contact has a characteristic intensity during the input that is below a predetermined intensity threshold, the device displays ( 1108 ) the first user interface representation for the first user interface and at least the second user interface representation for the second user interface on the display, where the first user interface representation is displayed over the second user interface representation and partially exposes the second user interface representation. For example, upon determining that the intensity of contact  602  does not reach a deep press intensity threshold (IT D ) in  FIGS. 6B-6C , user interface representation  508  is displayed over user interface representation  510  in  FIG. 6C . In some embodiments, the first user interface representation and the second user interface representation are displayed in a stack. 
     In some embodiments, in accordance with a determination that the first contact reaches an intensity during the input that is above the predetermined intensity threshold, the device enters ( 1110 ) a user interface selection mode and displays a plurality of user interface representations in a stack on the display, the stack including the first user interface representation displayed over and partially exposing the second user interface representation. For example, upon determining that the intensity of contact  608  reaches a deep press intensity threshold (IT D ) in  FIG. 6H , the device enters a user interface selection mode, including display of user interface representations  508 ,  510 , and  526 . 
     In some embodiments, display of the stack replaces display of the first user interface on the display. For example, user interface  506  including the stack replaces display of user interface  507  in  FIG. 6H . 
     In some embodiments, the stack of user interface representations is gradually spread out with the increasing contact intensity during the input. For example, as the intensity of contact  610  continues to increase in from  FIG. 6J  to  FIG. 6K , and then to maximum intensity in  FIG. 6L , user interface representations in the stack are spread out, as illustrated by movement of user interface representation  510  from location  510 -a in  FIG. 6J , through location  510 -b in  FIG. 6K , out to location  510 -c in  FIG. 6L , which is almost entirely off touch screen  112 . 
     In some embodiments, before the intensity reaches the predetermined threshold intensity, the stack is revealed in a “peek” mode, and reducing the contact intensity during the “peek” mode causes the previously expanded stack to retract. In some embodiments, a quick deep press input with intensity passing the predetermined threshold intensity causes the immediate display of the stack, skipping the peek mode. 
     In some embodiments, the first user interface corresponds ( 1112 ) to a first open application, and, at a time when the input by the first contact is received, the second user interface is a user interface of a second open application that was viewed just prior to displaying the first open application. E.g., the first and second user interface representations correspond to the last two applications open on the device. For example, as illustrated in  FIG. 6C , first user interface representation  508  is of first user interface  502 , which was displayed on touch screen  112  immediately preceding display of the user interface representations and second user interface representation  510  is of second user interface  507 , which was displayed on touch screen  112  immediately preceding display of first user interface  502 . 
     In some embodiments, the first user interface corresponds ( 614 ) to a first open application, and, at a time when the input by the first contact is received, the second user interface is a user interface of the first open application that was viewed just prior to displaying the first user interface of the first open application. E.g., the first and second user interface representations correspond to the last two user interfaces of the application that was open prior to peeking. 
     The method also includes, while displaying the first user interface representation and at least the second user interface representation on the display, the device detects ( 1116 ) termination of the input by the first contact (e.g., detecting lift off of the first contact or detecting the intensity of the first contact fall below a minimum intensity detection threshold, for example, detection of lift off of contact  602  in  FIGS. 6D and 6G ). 
     In response to detecting termination of the input by the first contact ( 618 ): in accordance with a determination that the first contact had a characteristic intensity (e.g., a representative intensity such as a maximum intensity) during the input that was below a predetermined intensity threshold (e.g., a deep press intensity threshold (IT D )) and the first contact moved during the input in a direction across the touch-sensitive surface that corresponds to a predefined direction on the display (e.g., rightward, in a drag or swipe gesture; or a movement of the contact to a location on the touch-sensitive surface that corresponds to a position over the second user interface representation in the stack on the display), the device displays ( 1120 ) a second user interface that corresponds to the second user interface representation. For example, in  FIGS. 6A, 6E-6G , device  100  determines that the intensity of contact  604  did not reach a predetermined deep press intensity threshold (IT D ), and the input included movement of contact  604  to the right. Thus, when lift off of contact  604  is detected, device  100  displays user interface  507 , corresponding to second user interface representation  510  during the peek gesture, as illustrated in  FIG. 6G . 
     In some embodiments, the second user interface is displayed without displaying other user interfaces that correspond to the plurality of user interface representations in the stack. In some embodiments, display of the second user interface replaces display of the stack on the display. In some embodiments, a light press followed by a swipe gesture results in a “peek” that includes display of a representation of the prior user interface followed by display of the prior user interface. In some embodiments, repeating the light press followed by a swipe gesture enables a user to quickly toggle between a current view and an immediately prior view (e.g., after toggling from first user interface  502  to second interface  507  in  FIG. 6G , the user performs the same light press input with movement in  FIGS. 6Q-6S  to toggle back to first user interface  502 , as illustrated in  FIG. 6S . 
     The method also includes, in accordance with a determination that the first contact had a characteristic intensity (e.g., a maximum intensity) during the input that was below the predetermined intensity threshold (e.g., deep press intensity threshold (IT D )) and the first contact did not move during the input in a direction across the touch-sensitive surface that corresponds to the predefined direction on the display (e.g., the first contact was stationary during the input or moved less than a threshold amount during the input), the device redisplays ( 1122 ) the first user interface. For example, in  FIGS. 6A-6D , device  100  determines that contact  602  did not reach a deep press intensity threshold (IT D ) and was stationary. Thus, when lift off of contact  602  is detected, device  100  redisplays first user interface  502 , as illustrated in  FIG. 6D . 
     In some embodiments, the first user interface is displayed without displaying other user interfaces that correspond to the plurality of user interface representations in the stack. In some embodiments, display of the first user interface replaces display of the stack on the display. In some embodiments, a stationary light press results in a “peek” that includes display of a representation of the prior user interface followed by redisplay of the current user interface. In some embodiments, complete release of the intensity during the “peek,” without additional movement of the first contact, causes the display to return to showing the first user interface. 
     In some embodiments, in response to detecting termination of the input by the first contact, in accordance with a determination that the first contact reached an intensity during the input that was above the predetermined intensity threshold (e.g., deep press intensity threshold (IT D )), the device maintains ( 1124 ) in the user interface selection mode and maintains display of the stack. For example, in  FIGS. 6H-6I , device  100  determines that contact  608  reached a deep press intensity threshold (IT D ). Thus, when lift off of contact  608  is detected, device  100  maintains display of the stack, as illustrated in  FIG. 6I . 
     In some embodiments, a deep press with intensity passing a predetermined threshold intensity results in display of the stack, which is maintained when the deep press input ends (e.g., as illustrated in  FIGS. 6H-6I ). In some embodiments, the stack includes at least user interface representations of all open applications and the user can navigate through the representations and select a desired application using subsequent inputs (e.g., drag gestures to the left or right in accordance with the operations described for method  1000 ). 
     In some embodiments, while displaying the second user interface on the display, the device detects ( 1126 ) a second input by a second contact on the touch-sensitive surface (e.g., contact  626  in  FIG. 6Q ). While detecting the second input by the second contact, the device redisplays ( 1128 ) the first user interface representation and at least the second user interface representation on the display (e.g., as illustrated in  FIG. 6R , where user interface representation  510  is now displayed over user interface representation  508 ). 
     In some embodiments, while redisplaying the first user interface representation and at least the second user interface representation on the display, the device detects ( 1130 ) termination of the second input by the second contact (e.g., lift off of contact  626 , as illustrated in  FIG. 6S ). In response to detecting termination of the second input by the second contact ( 1132 ): in accordance with a determination that the second contact had a characteristic intensity during the input that was below the predetermined intensity threshold (e.g., deep press intensity threshold (IT D )) and the second contact moved during the second input in a direction across the touch-sensitive surface that corresponds to the predefined direction on the display, the device redisplays ( 1134 ) the first user interface (e.g., toggles back from the second user interface to the first user interface, as illustrated in  FIG. 6S ). 
     In response to detecting termination of the second input by the second contact ( 1132 ): in accordance with a determination that the second contact had a characteristic intensity during the second input that was below the predetermined intensity threshold (e.g., deep press intensity threshold (IT D )) and the second contact did not move during the second input in a direction across the touch-sensitive surface that corresponds to the predefined direction on the display (e.g., the contact was stationary), the device redisplays ( 1136 ) the second user interface (e.g., the user has only peeked back at a representation of the first user interface, without toggling back. 
     In some embodiments, the input by the first contact includes a press input at a location on the touch-sensitive surface that corresponds to a first predetermined region on or near the display (e.g., the left edge of the display or bezel, for example, as illustrated in  FIGS. 6A-6D ). While displaying the first user interface on the display after detecting termination of the input by the first contact, the device detects ( 1138 ) a second input by a second contact on the touch-sensitive surface, where the second input by the second contact on the touch-sensitive surface is a press input at a location on the touch-sensitive surface that corresponds to a second predetermined region on or near the display (e.g., the right edge of the display or bezel, or somewhere within the first user interface) that is different from the first predetermined region. 
     In response to detecting the second input by the second contact on the touch-sensitive surface, the device performs ( 1140 ) a content-dependent operation associated with content of the first user interface (e.g., the content-dependent operation is selection or activation of an item in the first user interface, or any other content-specific operation associated with first user interface that is unrelated to the user interface selection mode). 
     In some embodiments, the first user interface is a view of a first application that includes a hierarchy of views (e.g., a webpage history or a navigation hierarchy). The input by the first contact includes a press input at or near a first edge of the touch-sensitive surface. After redisplaying the first user interface, the device detects ( 1142 ) an edge swipe gesture that originates from the first edge of the touch-sensitive surface. In response to detecting the edge swipe gesture that originates from the first edge of the touch-sensitive surface, the device displays ( 1144 ) a view in the hierarchy of views of the first application that precedes the first user interface (e.g., a previously viewed webpage). 
     In some embodiments, the first user interface is the user interface of a currently open application. In some embodiments, the first user interface is the current user interface of an application, which is preceded by a sequence of previous user interfaces for the application that are accessible by a “back” button provided on each of the user interfaces. 
     In some embodiments, while displaying the first user interface of the first application on the display, the device detects a drag gesture by a first contact on the touch-sensitive surface. In response to detecting the drag gesture by the first contact, in accordance with a determination that the drag gesture by the first contact occurs within an area of the touch-sensitive surface that corresponds to a first predefined area on or near the display, entering an application selection mode. In accordance with a determination that the drag gesture by the first contact occurs within an area of the touch-sensitive surface that corresponds to a second predefined area on or near the display that is distinct from the first predefined area, displaying a second user interface of the first application, on the display, that was displayed just prior to the display of the first user interface of the first application. 
     In some embodiments, the first predefined area is adjacent to the bottom edge of the display, and the second predefined area is at least a portion of the remainder of the display, e.g., an area above the first predefined area. In some embodiments, the drag gesture by the first contact, which occurs either within an area of the touch-sensitive surface that corresponds to the first predefined area or within an area of the touch-sensitive surface that corresponds to the second predefined area, is also required to start on an area of the touch-sensitive surface that corresponds to the left edge of the display or in an area of the touch-sensitive surface that corresponds to a predefined area adjacent to the left edge of the display (in order to either enter the application selection mode or display the second user interface. 
     In some embodiments, in accordance with the determination that the drag gesture by the first contact starts in an area of the touch-sensitive surface that corresponds to the first predefined area on the display, the device displays a plurality of user interface representations for a corresponding plurality of applications on the display, including a first user interface representation that corresponds to the first user interface of the first application and a second user interface representation that corresponds to a second user interface of a second application that is distinct from the first application. In some embodiments, display of the stack replaces display of the first user interface of the first application on the display. In some embodiments, the plurality of user interface representations are displayed in a stack. In some embodiments, the first user interface representation is displayed over and partially exposes the second user interface representation. 
     In some embodiments, after detecting termination of the input by the first contact, while displaying the stack in the user interface selection mode in accordance with the determination that the first contact reached an intensity during the input that was above the predetermined intensity threshold (e.g., as illustrated in  FIGS. 6H-6I ), the device detects ( 1146 ) a drag gesture by a second contact on the touch-sensitive surface at a location that corresponds to the second user interface representation on the display, where the drag gesture moves across the touch-sensitive surface in a direction that corresponds to a first direction on the display (e.g., as illustrated in  FIGS. 5G-5I ). 
     In response to detecting the drag gesture by the second contact on the touch-sensitive surface at a location corresponding to the second user interface representation on the display ( 1148 ), where the drag gesture moves across the touch-sensitive surface in a direction that corresponds to the first direction on the display, the device moves ( 1150 ) the second user interface representation in the first direction at a second speed based on a speed of the second contact (e.g., movement of user interface representation  510  from location  510 -a in  FIG. 5G  to location  510 -c in  FIG. 5I ); and the device moves ( 1152 ) the first user interface representation, disposed above the second user interface representation, in the first direction at a first speed greater than the second speed (e.g., movement of user interface representation  508  from location  508 -a in  FIG. 5G  to location  508 -b, and off the screen in  FIG. 5I ). In some embodiments, once the user interface selection mode is activated, it may be navigated according to the processes described above for method  1000 . 
     It should be understood that the particular order in which the operations in  FIGS. 11A-11E  have been described is merely exemplary and is not intended to indicate that the described order is the only order in which the operations could be performed. One of ordinary skill in the art would recognize various ways to reorder the operations described herein. Additionally, it should be noted that details of other processes described herein with respect to other methods described herein (e.g., methods  1000 ,  1200 ,  1300 ,  1400 ,  1500 ,  2400 , and  2500 ) are also applicable in an analogous manner to method  1000  described above with respect to  FIGS. 11A-11E . For example, the contacts, gestures, user interface objects, intensity thresholds, focus selectors, and animations described above with reference to method  1100  optionally have one or more of the characteristics of the contacts, gestures, user interface objects, intensity thresholds, focus selectors, and animations described herein with reference to other methods described herein (e.g., methods  1000 ,  1200 ,  1300 ,  1400 ,  1500 ,  2400 , and  2500 ). For brevity, these details are not repeated here. 
       FIGS. 12A-12E  illustrate a flow diagram of a method  1200  of navigating between user interfaces in accordance with some embodiments. The method  1200  is performed at an electronic device (e.g., device  300 ,  FIG. 3 , or portable multifunction device  100 ,  FIG. 1A ) with a display, a touch-sensitive surface, and one or more sensors to detect intensity of contacts with the touch-sensitive surface. In some embodiments, the display is a touch-screen display and the touch-sensitive surface is on or integrated with the display. In some embodiments, the display is separate from the touch-sensitive surface. In some embodiments, the touch-sensitive surface is part of a track pad or a remote control device that is separate from the display. In some embodiments, the operations in method  1000  are performed by an electronic device configured for management, playback, and/or streaming (e.g., from an external server) of audio and/or visual files that is in communication with a remote control and a display (e.g., Apple TV from Apple Inc. of Cupertino, Calif.). Some operations in method  1200  are, optionally, combined and/or the order of some operations is, optionally, changed. 
     As described below, the method  1200  provides an intuitive way to navigate between user interfaces. The method reduces the cognitive burden on a user when navigating between user interfaces, thereby creating a more efficient human-machine interface. For battery-operated electronic devices, enabling a user to navigate between user interfaces faster and more efficiently conserves power and increases the time between battery charges. 
     The device displays ( 1202 ) a first user interface on the display (e.g., user interface  502  in  FIG. 7A ). In some embodiments, the first user interface is the user interface of a currently open application. In some embodiments, the first user interface is the current user interface of an application, and display of the first user interface was preceded by display of a sequence of previous user interfaces of the application (e.g., previous web pages). In some embodiments, the previous user interfaces are accessible by activating a “back” button provided on the user interfaces of the application (e.g., back button  614  in  FIG. 7A . 
     While displaying the first user interface on the display, the device detects ( 1204 ), on the touch-sensitive surface, an input by a first contact that includes a period of increasing intensity of the first contact (e.g., contact  702  having increasing intensity in  FIGS. 7B-7E . In some embodiments, the input by the first contact is made with the flat portion of a thumb. 
     In response to detecting the input by the first contact that includes the period of increasing intensity of the first contact (e.g., contact  702 ), the device displays ( 1206 ) a first user interface representation for the first user interface and a second user interface representation for a second user interface (e.g., a user interface of a second application that was displayed just before the first user interface of the current application) on the display, wherein the first user interface representation is displayed over the second user interface representation and partially exposes the second user interface representation (e.g., user interface representations  508  and  510  in  FIG. 7C . 
     In some embodiments, the first user interface representation and the second user interface representation are displayed in a stack. In some embodiments, display of the stack replaces display of the first user interface on the display. 
     In some embodiments, the user interface enters a “peek” mode in response to a light press, and as the contact intensity increases or decreases after activation of the “peek” mode, a varying amount of the user interface representation for the previously displayed application is revealed from beneath the representation of the user interface of the current application (e.g., as the intensity of contact  702  increases from  FIG. 7C  to  FIG. 7D , more of user interface representation  510  is revealed from beneath user interface representation  508 ). 
     In some embodiments, before the period of increasing intensity of the first contact, the first contact has a period of varying intensity that includes both rising and falling intensities (e.g., the intensity of contact  704  rises from  FIG. 7G  to  FIG. 7H , falls from  FIG. 7H  to  FIG. 7I , and then increases again from  FIG. 7I  to  FIG. 7J . The device dynamically changes ( 1208 ) an area of the second user interface representation that is revealed from behind the first user interface representation in accordance with rising and falling of the intensity of the first contact during the period of varying intensity (e.g., more of user interface representation  508  is revealed when the intensity of contact  704  rises from  FIG. 7G  to  FIG. 7H ; less of user interface representation  508  is revealed when the intensity of contact  704  falls from  FIG. 7H  to  FIG. 7I , and then more of user interface representation  708  is revealed again when the intensity of contact  704  rises from  FIG. 7I  to  FIG. 7J . 
     The method also includes that, while displaying the first user interface representation and the second user interface representation on the display, the device detects ( 1210 ) that, during the period of increasing intensity of the first contact, the intensity of the first contact meets one or more predetermined intensity criteria (e.g., the intensity of the first contact is at or above a predetermined threshold intensity, such as a deep press intensity threshold (IT D ), as illustrated in  FIG. 7E ). 
     In some embodiments, during the period of increasing contact intensity of the first contact and before the intensity of the first contact meets the one or more predetermined intensity criteria, the device increases ( 1212 ) an area of the second user interface representation that is revealed from behind the first user interface representation in accordance with an increase in intensity of the first contact. For example, as the intensity of contact  702  increases from  FIG. 7C  to  FIG. 7D , more of user interface representation  510  is revealed from beneath user interface representation  508 . In some embodiments, the second user interface is displayed larger (e.g., as if coming towards the user from behind the plane of the display) in response to increasing intensity of the contact. 
     In some embodiments, increasing the area of the second user interface representation that is revealed from behind the first user interface representation in accordance with the increase in intensity of the first contact includes displaying ( 1214 ) an animation that dynamically changes the amount of area of the second user interface representation that is revealed from behind the first user interface representation based on changes in the intensity of the first contact over time. 
     In some embodiments, dynamically changing the amount of area includes updating the amount of area of the second user interface multiple times a second (e.g., 10, 20, 30, or 60 times per second), optionally without regard to whether or not the contact meets the one or more predetermined intensity criteria. In some embodiments, the animation is a fluid animation that is updated as the intensity of the first contact changes, so as to provide feedback to the user as to the amount of intensity detected by the device (e.g., feedback as to the amount of force applied by the user). In some embodiments the animation is updated smoothly and quickly so as to create the appearance for the user that the user interface is responding in real-time to changes in force applied to the touch-sensitive surface (e.g., the animation is perceptually instantaneous for the user so as to provide immediate feedback to the user and enable the user to better modulate the force that they are applying to the touch-sensitive surface to interact efficiently with user interface objects that are responsive to contacts with different or changing intensity). 
     In some embodiments, increasing the area of the second user interface representation that is revealed from behind the first user interface representation in accordance with the increase in intensity of the first contact includes moving ( 1216 ) the first user interface representation in a first direction to increase a lateral position offset on the display between the first user interface representation and the second user interface representation. For example, as the intensity of contact  704  increases from  FIG. 7G  to  FIG. 7H , user interface representation  510  slides to the right, from location  510 -a in  FIG. 7G  to location  510 -b in  FIG. 7H , revealing more of user interface representation  508 . In some embodiments, as a finger contact presses harder on the touch-sensitive surface at a location that corresponds to the left edge of the display or a predefined area adjacent to the left edge of the display, the first user interface representation moves to the left to reveal more of the second user interface representation. 
     In some embodiments, increasing the area of the second user interface representation that is revealed from behind the first user interface representation in accordance with the increase in intensity of the first contact includes, while moving the first user interface representation in the first direction to increase the lateral position offset on the display between the first user interface representation and the second user interface representation, moving ( 718 ) the first user interface representation and the second user interface representation towards each other in a second direction perpendicular to the first direction (e.g., as the intensity of contact  702  increases from  FIG. 7C  to  FIG. 7D , first user interface representation  508  appears to move away from the surface of touch screen  112 , and second user interface representation  510  appears to move towards the surface of the touch screen. In some embodiments, the second direction perpendicular to the first direction is the z-direction perpendicular to the surface of the display. In some embodiments, the first user interface representation and the second user interface representation move towards a same layer in a z-layer order. 
     In some embodiments, the device detects ( 1220 ) that the intensity of the first contact meets the one or more predetermined intensity criteria (e.g., deep press intensity threshold (IT D ), as illustrated in  FIG. 7E ). In response to detecting that the intensity of the first contact meets the one or more predetermined intensity criteria, the device displays ( 1222 ) an animation showing the first user interface representation receding behind the second user interface representation and the second user interface representation moving into the foreground and transitioning to the second user interface (e.g., user interface representation  510  pops out from behind user interface representation  508 , as illustrated in  FIG. 7E , and then an animation transitions the display into user interface  507  in  FIG. 7F ). 
     In some embodiments, the device changes ( 1224 ) a level of blurring effect applied to at least one of the first user interface representation and the second user interface representation during the animation. E.g., the first user interface representation becomes more blurred and/or the second user interface representation becomes less blurred during the animation, as illustrated in the series of  FIGS. 7C-7E , where user interface representation  510  starts off blurry in  FIG. 7C  and comes into focus as it appears to move towards the surface of touch screen  112 . In contrast, user interface  508  starts off in focus in  FIG. 7C  and becomes blurry as it appears to move away from the surface of touch screen  112 . 
     The method also includes that, in response to detecting that the intensity of the first contact meets the one or more predetermined intensity criteria ( 1226 ): the device ceases to display ( 1228 ) the first user interface representation and the second user interface representation on the display; and the device displays ( 1230 ) the second user interface on the display (e.g., without displaying the first user interface). In some embodiments, the “peek” is followed by a “pop” that displays the second user interface, when the contact intensity reaches or exceeds a predetermined deep press threshold intensity. For example, when the intensity of contacts  702 ,  704 , and  706  reach a deep press intensity threshold (ITD) in  FIGS. 7F, 7J, and 70 , respectively, the user second user interface representation “pops,” and the device displays the corresponding user interface. 
     In some embodiments, while displaying the second user interface on the display, the device detects ( 1232 ), on the touch-sensitive surface, an input by a second contact that includes a period of increasing intensity of the second contact (e.g., contact  706  having increasing intensity in  FIGS. 7L to 7O ). 
     In response to detecting the input by the second contact that includes the period of increasing intensity of the second contact, the device displays ( 1234 ) the first user interface representation and the second user interface representation on the display, wherein the second user interface representation is displayed over the first user interface representation and partially exposes the first user interface representation (e.g., display of user interface representations  508  and  510  in  FIG. 7M ). 
     In some embodiments, the first user interface representation and the second user interface representation are displayed in a second stack. In some embodiments, display of the second stack replaces display of the second user interface on the display. 
     In some embodiments, the user interface enters a “peek” mode in response to a light press, and as the contact intensity increases or decreases after activation of the “peek” mode, a varying amount of the user interface representation for the previously displayed application is revealed from beneath the representation of the user interface of the current application. For example, more of user interface representation  508  is revealed from behind user interface representation  510  in response to detection of an increasing intensity of contact  706  in  FIGS. 7M-7N . 
     In some embodiments, while displaying the first user interface representation and the second user interface representation on the display, the device detects ( 1236 ) that, during the period of increasing intensity of the second contact, the intensity of the second contact meets the one or more predetermined intensity criteria. 
     In response to detecting that the intensity of the second contact meets the one or more predetermined intensity criteria ( 1238 ), the device ceases to display ( 1240 ) the first user interface representation and the second user interface representation on the display; and the device displays ( 1242 ) the first user interface on the display (e.g., without displaying the second user interface). For example, device  100  detects that the intensity of contact  706  exceeds a deep press intensity threshold (ITD), and in response replaces display of user interface  506  with first user interface  508  in  FIG. 7O . In some embodiments, the “peek” is followed by a “pop” that displays the first user interface, when the contact intensity reaches or exceeds a predetermined deep press threshold intensity. 
     In some embodiments, while displaying the second user interface on the display, the device detects ( 1244 ), on the touch-sensitive surface, an input by a second contact that includes a period of increasing intensity of the second contact. (e.g., contact  704  having increasing intensity in  FIGS. 7G-7H ) 
     In response to detecting the input by the second contact that includes the period of increasing intensity of the second contact, the device displays ( 1246 ) the first user interface representation and the second user interface representation on the display, wherein the second user interface representation is displayed over the first user interface representation and partially exposes the first user interface representation (e.g., display of user interface representations  508  and  510  in  FIG. 7M ). 
     In some embodiments, the first user interface representation and the second user interface representation are displayed in a second stack. In some embodiments, display of the second stack replaces display of the second user interface on the display. 
     In some embodiments, the user interface enters a “peek” mode in response to a light press, and as the contact intensity increases or decreases after activation of the “peek” mode, a varying amount of the user interface representation for the previously displayed application is revealed from beneath the representation of the user interface of the current application. For example, more of user interface representation  508  is revealed from behind user interface representation  510  in response to detection of an increasing intensity of contact  704  in  FIGS. 7G-7H . 
     While displaying the first user interface representation and the second user interface representation on the display, the device detects ( 1248 ) termination of the input by the second contact (e.g., detecting lift off of the second contact (e.g., as in  FIG. 7K ) or detecting the intensity of the second contact fall below a minimum intensity detection threshold (e.g., as in  FIG. 7J )) without the intensity of the second contact having met the one or more predetermined intensity criteria. 
     In response to detecting termination of the input by the second contact without the intensity of the second contact having met the one or more predetermined intensity criteria ( 1250 ): the device ceases to display ( 1252 ) the first user interface representation and the second user interface representation on the display; and the device displays ( 1254 ) the second user interface on the display (e.g., without displaying the first user interface). For example, device  100  detects that the intensity of contact  704  falls below a minimum intensity detection threshold (ITO, and in response replaces display of user interface  506  with second user interface  510  in  FIG. 7J . In some embodiments, when the input terminates without the contact intensity reaching a predetermined deep press threshold intensity, the “peek” ceases and the second user interface is redisplayed. 
     It should be understood that the particular order in which the operations in  FIGS. 12A-12E  have been described is merely exemplary and is not intended to indicate that the described order is the only order in which the operations could be performed. One of ordinary skill in the art would recognize various ways to reorder the operations described herein. Additionally, it should be noted that details of other processes described herein with respect to other methods described herein (e.g., methods  1000 ,  1100 ,  1300 ,  1400 ,  1500 ,  2400 , and  2500 ) are also applicable in an analogous manner to method  1200  described above with respect to  FIGS. 10A-10H . For example, the contacts, gestures, user interface objects, intensity thresholds, focus selectors, and animations described above with reference to method  1200  optionally have one or more of the characteristics of the contacts, gestures, user interface objects, intensity thresholds, focus selectors, and animations described herein with reference to other methods described herein (e.g., methods  1000 ,  1100 ,  1300 ,  1400 ,  1500 ,  2400 , and  2500 ). For brevity, these details are not repeated here. 
       FIGS. 13A-13D  illustrate a flow diagram of a method  1300  of navigating between user interfaces in accordance with some embodiments. The method  1300  is performed at an electronic device (e.g., device  300 ,  FIG. 3 , or portable multifunction device  100 ,  FIG. 1A ) with a display, a touch-sensitive surface, and one or more sensors to detect intensity of contacts with the touch-sensitive surface. In some embodiments, the display is a touch-screen display and the touch-sensitive surface is on or integrated with the display. In some embodiments, the display is separate from the touch-sensitive surface. In some embodiments, the touch-sensitive surface is part of a track pad or a remote control device that is separate from the display. In some embodiments, the operations in method  1000  are performed by an electronic device configured for management, playback, and/or streaming (e.g., from an external server) of audio and/or visual files that is in communication with a remote control and a display (e.g., Apple TV from Apple Inc. of Cupertino, Calif.). Some operations in method  1300  are, optionally, combined and/or the order of some operations is, optionally, changed. 
     As described below, the method  1300  provides an intuitive way to navigate between user interfaces. The method reduces the cognitive burden on a user when navigating between user interfaces, thereby creating a more efficient human-machine interface. For battery-operated electronic devices, enabling a user to navigate between user interfaces faster and more efficiently conserves power and increases the time between battery charges. 
     The device displays ( 1302 ) a plurality of user interface representations in a stack on the display, (e.g., in a user interface selection mode, displaying a stack of cards (or other objects) in a z-layer order representing user interfaces of open applications, cards representing current and previously viewed user interfaces of a single application, cards representing messages in an e-mail chain, etc.). At least a first user interface representation, a second user interface representation, and a third user interface representation are visible on the display. The first user interface representation (e.g., user interface representation  508  in  FIG. 8A ) is laterally offset from the second user interface representation in a first direction (e.g., laterally offset to the right on the display) and partially exposes the second user interface representation. The second user interface representation (e.g., user interface representation  510  in  FIG. 8A ) is laterally offset from the third user interface representation (e.g., user interface representation  526  in  FIG. 8A ) in the first direction (e.g., laterally offset to the right on the display) and partially exposes the third user interface representation. For example, in some embodiments, the stack is displayed when the display is in a user interface selection mode, as shown in  FIG. 8A . 
     In some embodiments, prior to displaying the stack on the display ( 1304 ): the device displays ( 1306 ) a first user interface that corresponds to the first user interface representation on the display (e.g., user interface  502  of a web browsing application, as illustrated in  FIG. 7A ). While displaying the first user interface, the device detects ( 1308 ) a predetermined input. In some embodiments, the predetermined input is, for example, a double-tap or double press on the “home” button on the device; or, for an electronic device that includes one or more sensors to detect intensity of contacts with a touch-sensitive display; a deep press on a predetermined area of the first user interface (e.g., an upper left corner); a deep press with the flat portion of a thumb anywhere on the first user interface; or a deep press on a predetermined area of the device, such as on the left edge of the touch-sensitive display, in a predefined area adjacent to the left edge of the touch-sensitive display, on the bottom edge of the touch-sensitive display, or in a predefined area adjacent to the bottom edge of the touch-sensitive display. 
     In response to detecting the predetermined input ( 1310 ): The device enters ( 1313 ) a user interface selection mode; and the device displays ( 1312 ) the stack comprising the plurality of user interface representations (e.g., display of user interface  506  of a user interface selection mode including display of a stack in  FIG. 9A ). 
     In some embodiments, the stack is displayed ( 1316 ) in response to detecting an input by the first contact (e.g., a press input with an intensity above a predefined threshold) when the first contact is at a first location on the touch-sensitive surface that corresponds to an onscreen location other than the second user interface representation (e.g., contact  806  is detected at location  806 -a, which does not correspond with display of user interface representation  510  on touch screen  112  in  FIGS. 8J-8K ). The first contact moves on the touch-sensitive surface from the first location to the location that corresponds to the second user interface representation on the display before the increase in intensity of the first contact is detected (e.g., contact  806 -a moves from location  806 -a to location  806 -b in  FIG. 8K-8L ). For example, the first contact is continuously detected on the device from before the time that the second user interface representation is displayed until at least the time that the increased area of the second user interface representation that is exposed from behind the first user interface representation is displayed. 
     The method also includes that the device detects ( 1318 ) an input by a first contact on the touch sensitive surface at a location that corresponds to the second user interface representation on the display (e.g., contact  802  at a location corresponding to display of user interface representation  510  on touch screen  112  in  FIG. 8A ). In some embodiments, the device detects a press by a finger contact at a location on the touch-sensitive surface that corresponds to a user interface representation in the stack, and the device detects a varying intensity of the finger contact (e.g., the intensity of contact  802  increases from  FIG. 8A  to  FIG. 8B , decreases from  FIG. 8B  to  FIG. 8C , and then increases again from  FIG. 8C  to  FIG. 8D ). 
     In some embodiments, the input by the first contact includes a period of decreasing intensity of the first contact following a period of increasing intensity of the first contact. During the period of decreasing intensity of the first contact, the device decreases ( 1320 ) the area of the second user interface representation that is exposed from behind the first user interface representation by decreasing the lateral offset between the first user interface representation and the second user interface representation. For example, in response to the decreasing intensity of contact  802  from  FIG. 8B  to  FIG. 8C , user interface representation  508  starts to slide back over user interface representation  510 , moving from location  508 -b in  FIG. 8B  to location  508 -c in  FIG. 8C . 
     In some embodiments, after revealing more of the second user interface representation in response to detecting an increase in the contact intensity, the device reveals less of the second user interface representation in response to detecting a decrease in the contact intensity (e.g., in response to increasing intensity of contact  802  from  FIG. 8A  to  FIG. 8B , user interface representation  508  slides to the right of user interface representation  510 , moving from location  508 -a in  FIG. 8A  to location  508 -b in  FIG. 8B ). In some embodiments, an animation is displayed to show movement of the first user interface representation and the second user interface representation in a manner that dynamically responds to small changes in the intensity of the first contact (e.g., movement of user interface representation  508  in  FIGS. 8A-8C  is directly manipulated by the user increasing or decreasing the intensity of contact  802 . 
     The method also includes that, in accordance with detecting an increase in intensity of the first contact on the touch-sensitive surface at the location that corresponds to the second user interface representation on the display, the device increases ( 1322 ) an area of the second user interface representation that is exposed from behind the first user interface representation by increasing the lateral offset between the first user interface representation and the second user interface representation (e.g., in response to increasing intensity of contact  802  from  FIG. 8A  to  FIG. 8B , user interface representation  508  slides to the right of user interface representation  510 , moving from location  508 -a in  FIG. 8A  to location  508 -b in  FIG. 8B  and revealing more of user interface representation  810 ). 
     In some embodiments, the second user interface representation (e.g., user interface representation  510  in  FIGS. 8A-8C ) is positioned below the first user interface representation (e.g., user interface representation  508  in  FIGS. 8A-8C ) and above the third user interface representation (e.g., user interface representation  526  in  FIGS. 8A-8C ) in a z-layer order, and a press by the contact at a location on the touch-sensitive surface that corresponds to the exposed portion of the second user interface representation reveals more of the second user interface representation. In some embodiments, to reveal more of the second user interface representation, the first user interface representation moves to the right in response to detecting an increasing intensity of the contact at a location on the touch-sensitive surface that corresponds to the exposed portion of the second user interface representation, thereby “peeking” at more of the second user interface representation (e.g., movement of user interface  508  from location  508 -a in  FIG. 8A  to location  508 -b in  FIG. 8B  in response to increasing intensity of contact  802  reveals more of user interface representation  510 ). 
     In some embodiments, increasing the area of the second user interface representation that is exposed from behind the first user interface representation includes moving ( 1324 ) the first user interface representation in the first direction (e.g., moving the first user interface representation to the right to increase the lateral offset between the first user interface representation and the second user interface representation). For example, user interface representation  508  moves to the right to reveal more of user interface representation  510  in  FIGS. 8A-8B . 
     In some embodiments, increasing the area of the second user interface representation that is exposed from behind the first user interface representation includes moving ( 1326 ) the second user interface representation in a second direction that is opposite the first direction (e.g., moving the second user interface representation to the left (with or without concurrent movement of the first user interface representation to the right), to increase the lateral offset between the first user interface representation and the second user interface representation on the display). For example, user interface representation  510  moves to the left to reveal more of the representation in  FIGS. 8G-8H . 
     In some embodiments, while displaying the stack, the device detects ( 1328 ) a drag gesture by a second contact on the touch-sensitive surface at a location that corresponds to the second user interface representation and that moves across the touch-sensitive surface in a direction that corresponds to a second direction that is opposite the first direction on the display; and (e.g., detecting a leftward drag on the touch-sensitive surface at a location that corresponds to the second user interface representation). 
     In response to detecting the drag gesture by the second contact on the touch-sensitive surface at a location that corresponds to the second user interface representation in a direction on the touch-sensitive surface that corresponds to the second direction on the display ( 1330 ) the device: moves ( 1332 ) the second user interface representation in the second direction at a second speed on the display based on a speed of the second contact on the touch-sensitive surface; moves ( 1334 ) the first user interface representation in the second direction at a first speed greater than the second speed; moves ( 1336 ) the third user interface representation in the second direction at a third speed less than the second speed; and moves ( 1338 ) a fourth user interface representation in the second direction at a fourth speed greater than the second speed. In some embodiments, the fourth speed is greater than the first speed. In some embodiments, the fourth user interface representation is disposed on top of the first user interface representation in the stack. 
     In some embodiments, in response to a prior drag gesture to the right, the fourth user interface representation was moved off the display to the right. A subsequent drag gesture to the left causes the fourth user interface representation to come into view on the display from the right (e.g., a drag gesture including contact  546  and movement  548  from location  546 -c in  FIG. 5L , through location  546 -e in  FIG. 5M , to location  546 -f in  FIG. 5N  causes user interface representation  508  to come back into view on the display from the right. In some embodiments, the speed of the fourth user interface representation is faster than any user interface representations below it in relative z-position. 
     In some embodiments, the device detects ( 1340 ) that the intensity of the first contact on the touch-sensitive surface at a location that corresponds to the second user interface representation meets one or more predetermined intensity criteria (e.g., the intensity of the first contact is at or above a predetermined threshold intensity, such as a deep press intensity threshold, as illustrated in  FIG. 8D ). 
     In response to detecting that the intensity of the first contact on the touch-sensitive surface at the location that corresponds to the second user interface representation meets the one or more predetermined intensity criteria ( 1342 ) the device: ceases to display ( 1342 ) the stack; and displays ( 1348 ) a second user interface that corresponds to the second user interface representation. For example, in response to detecting that the intensity of contact  802  exceeds a deep press intensity threshold (ITD) when at a location on touch screen  112  corresponding to display of user interface representation, device  100  replaces display of user interface  506  (corresponding to a user interface selection mode) with display of user interface  507  (corresponding to user interface representation  510 ) in  FIGS. 8C-8D . In some embodiments, the second user interface is displayed without displaying any user interfaces that correspond to other user interface representations in the stack. In some embodiments, the display of the second user interface replaces the display of the stack. 
     In some embodiments, in response to detecting that the intensity of the first contact on the touch-sensitive surface at the location that corresponds to the second user interface representation meets the one or more predetermined intensity criteria, the device displays an animation of the second user interface representation transitioning to the second user interface. For example, in response to detecting that the intensity of contact  802  exceeds a deep press intensity threshold (ITD) when at a location on touch screen  112  corresponding to display of user interface representation, device  100  displays an animation where first user interface representation  508  completely slides off second user interface representation  510  to the right, second user interface  510  appears to be lifted from the stack (e.g., passing through location  510 -b in  FIG. 8E  to location  510 -c in  FIG. 8F ), and first user interface representation  508  is shuffled back into the stack below second user interface representation  510  as the device transitions into display of user interface  507 , as illustrated in the series of  FIGS. 8C, 8E, and 8F . 
     In some embodiments, the device detects ( 1350 ) movement of the first contact from a location on the touch sensitive surface that corresponds to the second user interface representation to a location on the touch-sensitive surface that corresponds to the third user interface representation on the display, where an intensity of the first contact during the movement of the first contact is less than a characteristic intensity detected during the increase in intensity of the first contact at a location on the touch-sensitive surface that corresponds to the second user interface representation (e.g., device  100  detects movement  808  of contact  806  from location  806 -b in  FIG. 8N , corresponding to display of user interface representation  510 , to location  806 -c in  FIG. 8O , corresponding to display of user interface representation  526 ). 
     In accordance with detecting an increase in intensity of the first contact on the touch-sensitive surface at the location that corresponds to the third user interface representation on the display, the device increases ( 1352 ) an area of the third user interface representation that is exposed from behind the second user interface representation by increasing the lateral offset between the second user interface representation and the third user interface representation (e.g., device  100  detects an increase in the intensity of contact  806  from  FIG. 8O  to  FIG. 8P , and in response moves user interface representations  510  and  508  to the right, from locations  510 -a and  508 -a in  FIG. 8O  to locations  510 -h and  508 -h in  FIG. 8P , respectively, to reveal more of user interface  526 ). In some embodiments, only the user interface representation directly above the selected user interface representation (e.g., rather than all user interface representation above the selected user interface representation) is moved out of the way to reveal more of the selected user interface representation. For example, only user interface representation  510  would be moved in  FIG. 8O , to reveal more of user interface representation  526  (e.g., by sliding further under user interface representation  508 ). 
     In some embodiments, as the user drags their finger over different representations in the stack, the stack spreads apart to reveal more of the representation under the user&#39;s finger. In some embodiments, the user can increase intensity of the contact to peek at one representation, reduce intensity (without lifting off), move to the next representation, increase intensity to peek at the next representation, reduce intensity (without lifting off), move to another representation, and so on. 
     It should be understood that the particular order in which the operations in  FIGS. 13A-13D  have been described is merely exemplary and is not intended to indicate that the described order is the only order in which the operations could be performed. One of ordinary skill in the art would recognize various ways to reorder the operations described herein. Additionally, it should be noted that details of other processes described herein with respect to other methods described herein (e.g., methods  1000 ,  1100 ,  1200 ,  1400 ,  1500 ,  2400 , and  2500 ) are also applicable in an analogous manner to method  1300  described above with respect to  FIGS. 13A-13D . For example, the contacts, gestures, user interface objects, intensity thresholds, focus selectors, and animations described above with reference to method  1300  optionally have one or more of the characteristics of the contacts, gestures, user interface objects, intensity thresholds, focus selectors, and animations described herein with reference to other methods described herein (e.g., methods  1000 ,  1100 ,  1200 ,  1400 ,  1500 ,  2400 , and  2500 ). For brevity, these details are not repeated here. 
       FIGS. 14A-14C  illustrate a flow diagram of a method  1400  of navigating between user interfaces in accordance with some embodiments. The method  1400  is performed at an electronic device (e.g., device  300 ,  FIG. 3 , or portable multifunction device  100 ,  FIG. 1A ) with a display, a touch-sensitive surface, and optionally one or more sensors to detect intensity of contacts with the touch-sensitive surface. In some embodiments, the display is a touch-screen display and the touch-sensitive surface is on or integrated with the display. In some embodiments, the display is separate from the touch-sensitive surface. In some embodiments, the touch-sensitive surface is part of a track pad or a remote control device that is separate from the display. In some embodiments, the operations in method  1000  are performed by an electronic device configured for management, playback, and/or streaming (e.g., from an external server) of audio and/or visual files that is in communication with a remote control and a display (e.g., Apple TV from Apple Inc. of Cupertino, Calif.). Some operations in method  1400  are, optionally, combined and/or the order of some operations is, optionally, changed. 
     As described below, the method  1400  provides an intuitive way to navigate between user interfaces. The method reduces the cognitive burden on a user when navigating between user interfaces, thereby creating a more efficient human-machine interface. For battery-operated electronic devices, enabling a user to navigate between user interfaces faster and more efficiently conserves power and increases the time between battery charges. 
     The device displays ( 1402 ) a plurality of user interface representations in a stack on the display, (e.g., in a user interface selection mode, displaying a stack of cards (or other objects) in a z-layer order representing user interfaces of open applications, cards representing current and previously viewed user interfaces of a single application, cards representing messages in an e-mail chain, etc.). At least a first user interface representation, a second user interface representation, and a third user interface representation are visible on the display (e.g., a stack displaying user interface representations  508 ,  510 , and  526 , as illustrated in  FIG. 9A ). The second user interface representation (e.g., user interface representation  510  in  FIG. 9A ) is laterally offset from the first user interface representation in a first direction (e.g., laterally offset to the right on the display) and partially exposes the first user interface representation (e.g., user interface representation  526  in  FIG. 9A ). The third user interface representation (e.g., user interface representation  508  in  FIG. 9A ) is laterally offset from the second user interface representation in the first direction (e.g., laterally offset to the right on the display) and partially exposes the second user interface representation. 
     The device detects ( 1404 ) a drag gesture by a first contact that moves across the touch-sensitive surface, where movement of the drag gesture by the first contact corresponds to movement across one or more of the plurality of user interface representations in the stack. For example, a drag gesture including contact  902  and movement  904  in  FIG. 9B . 
     During the drag gesture, when the first contact moves over a location on the touch-sensitive surface that corresponds to the first user interface representation on the display, the device reveals ( 1406 ) more of the first user interface representation from behind the second user interface representation on the display. For example, as contact  902  moves over user interface representation  526 , user interface representations  510  and  508  move to the right to reveal more of user interface representation  526  in  FIG. 9B . 
     In some embodiments, revealing more of the first user interface representation from behind the second user interface representation includes moving ( 1408 ) the second user interface representation in the first direction (e.g., moving the second user interface representation to the right to increase the lateral offset between the first user interface representation and the second user interface representation). 
     In some embodiments, revealing more area of the first user interface representation from behind the second user interface representation includes moving ( 1410 ) the first user interface representation in a second direction that is opposite the first direction (e.g., moving the first user interface representation to the left (with or without concurrent movement of the second user interface representation to the right), to increase the lateral offset between the first user interface representation and the second user interface representation on the display). 
     In some embodiments, during the drag gesture, when the first contact moves ( 1412 ) from a first location on the touch-sensitive surface that corresponds to the first user interface representation to a second location on the touch-sensitive surface that corresponds to the second user interface representation (e.g., movement of contact  902  from location  902 -a, corresponding to display of user interface representation  526  in  FIG. 9B  to location  904  corresponding to display of user interface representation  510  in  FIG. 9C ): the device reveals ( 1414 ) more of the second user interface representation from behind the third user interface representation on the display, and reveals ( 1416 ) less of the first user interface representation from behind the second user interface representation on the display (e.g., user representation  510  moves to the left revealing more of its user interface representation and covering more of user interface representation  526  in  FIG. 9D ). 
     In some embodiments, while the first contact is at a location on the touch-sensitive surface that corresponds to one of the plurality of user interface representations in the stack, the device detects ( 1418 ) lift-off of the first contact (e.g., device  100  detects lift off of contact  902  in  FIG. 9E ). In response to detecting lift-off of the first contact ( 1420 ): the device ceases to display ( 1422 ) the stack; and the device displays ( 1424 ) a user interface that corresponds to said one of the plurality of user interface representations (e.g., device  100  replaces display of user interface  506  in  FIG. 9E  with display of user interface  507  in  FIG. 9F ). 
     For example, if the first contact in the drag gesture lifts off while over a location that corresponds to the first user interface representation, then the first user interface is displayed. If the first contact in the drag gesture lifts off while over a location that corresponds to the second user interface representation, then the second user interface is displayed. More generally, if the first contact in the drag gesture lifts off while over a location that corresponds to a respective user interface representation, then the corresponding user interface is displayed. In some embodiments, display of the user interface that corresponds to said one of the plurality of user interface representations replaces display of the stack. 
     In some embodiments, wherein the device has one or more sensors to detect intensity of contacts with the touch-sensitive surface, while the first contact is at a location on the touch-sensitive surface that corresponds to one of the plurality of user interface representations in the stack, the device detects ( 1426 ) that an intensity of the first contact meets one or more predetermined intensity criteria (e.g., the intensity of the first contact is at or above a predetermined threshold intensity, such as a deep press intensity threshold, as illustrated in  FIG. 9G ). 
     In response to detecting the intensity of the first contact meets one or more predetermined intensity criteria ( 1428 ): the device ceases to display ( 1430 ) the stack; and the device displays ( 1432 ) a user interface corresponding to said one of the plurality of user interface representations (e.g., device  100  replaces display of user interface  506  in  FIG. 9G  with display of user interface  507  in  FIG. 9H ). 
     For example, if the first contact in the drag gesture makes a deep press while over a location that corresponds to the first user interface representation, then the first user interface is displayed. If the first contact in the drag gesture makes a deep press while over a location that corresponds to the second user interface representation, then the second user interface is displayed. More generally, if the first contact in the drag gesture makes a deep press while over a location that corresponds to a respective user interface representation, then the corresponding user interface is displayed. In some embodiments, display of the user interface that corresponds to said one of the plurality of user interface representations replaces display of the stack. 
     It should be understood that the particular order in which the operations in  FIG. 1400  have been described is merely exemplary and is not intended to indicate that the described order is the only order in which the operations could be performed. One of ordinary skill in the art would recognize various ways to reorder the operations described herein. Additionally, it should be noted that details of other processes described herein with respect to other methods described herein (e.g., methods  1000 ,  1100 ,  1200 ,  1300 ,  1500 ,  2400 , and  2500 ) are also applicable in an analogous manner to method  1400  described above with respect to  FIGS. 14A-14C . For example, the contacts, gestures, user interface objects, intensity thresholds, focus selectors, and animations described above with reference to method  1400  optionally have one or more of the characteristics of the contacts, gestures, user interface objects, intensity thresholds, focus selectors, and animations described herein with reference to other methods described herein (e.g., methods  1000 ,  1100 ,  1200 ,  1300 ,  1500 ,  2400 , and  2500 ). For brevity, these details are not repeated here. 
       FIG. 15A  illustrates a flow diagram of a method  1500  of navigating between user interfaces in accordance with some embodiments. The method  1500  is performed at an electronic device (e.g., device  300 ,  FIG. 3 , or portable multifunction device  100 ,  FIG. 1A ) with a display, a touch-sensitive surface, and one or more sensors to detect intensity of contacts with the touch-sensitive surface. In some embodiments, the display is a touch-screen display and the touch-sensitive surface is on or integrated with the display. In some embodiments, the display is separate from the touch-sensitive surface. In some embodiments, the touch-sensitive surface is part of a track pad or a remote control device that is separate from the display. In some embodiments, the operations in method  1000  are performed by an electronic device configured for management, playback, and/or streaming (e.g., from an external server) of audio and/or visual files that is in communication with a remote control and a display (e.g., Apple TV from Apple Inc. of Cupertino, Calif.). Some operations in method  1500  are, optionally, combined and/or the order of some operations is, optionally, changed. 
     As described below, the method  1500  provides an intuitive way to navigate between user interfaces. The method reduces the cognitive burden on a user when navigating between user interfaces, thereby creating a more efficient human-machine interface. For battery-operated electronic devices, enabling a user to navigate between user interfaces faster and more efficiently conserves power and increases the time between battery charges. 
     The device displays ( 1502 ) a first user interface of a first application on the display. The first user interface including a backwards navigation control (e.g., user interface 6M including backwards navigation control icon  614 ). In some embodiments, the backwards navigation control is a back button or other icon that when activated (e.g., by a tap gesture) causes the device to replace display of the current user interface in an application with display of the prior user interface displayed in the application. In some embodiments, the first user interface is the current user interface of an application, whose display was preceded by the display of a sequence of previous user interfaces of the application. In some embodiments, the sequence of previous user interfaces of the application is navigated, in reverse chronological order, by activating a backwards navigation control provided on the user interfaces. 
     In some embodiments, the user interfaces for an application are arranged in a hierarchy and the backwards navigation control is a back button or other icon that when activated (e.g., by a tap gesture) causes the device to replace display of the current user interface in a first level of the hierarchy with display of a prior user interface at a second level in the hierarchy, where the second level is adjacent to and higher than the first level in the hierarchy. In some embodiments, the first user interface is the current user interface of an application, whose display was preceded by the display of a sequence of previous user interfaces in the hierarchy. In some embodiments, a hierarchical sequence of user interfaces for an application is navigated, in reverse hierarchical order, by activating a backwards navigation control. For example, a hierarchical sequence in an email application (including a multiple levels of mailboxes and inboxes) is navigated, in reverse hierarchical order, by activating a backwards navigation control that is provided on the user interfaces. 
     While displaying the first user interface of the first application on the display, the device detects ( 1504 ) a gesture by a first contact on the touch-sensitive surface at a location that corresponds to the backwards navigation control on the display (e.g., a tap gesture including contact  612  in  FIG. 6M  or a tap gesture including contact  624  in  FIG. 6O ). 
     In response to detecting the gesture by the first contact on the touch-sensitive surface at a location that corresponds to the backwards navigation control ( 1506 ): in accordance with a determination that the gesture by the first contact is a gesture (e.g., a stationary deep press gesture) with an intensity of the first contact that meets one or more predetermined intensity criteria (e.g., the intensity of the first contact during the gesture meets or exceeds a predetermined threshold intensity, such as a deep press intensity threshold), the device replaces ( 1508 ) display of the first user interface of the first application with display of a plurality of representations of user interfaces of the first application, including a representation of the first user interface and a representation of a second user interface. For example, device  100  determines that contact  612  includes an intensity satisfying a deep press intensity threshold, and in response, displays user interface representations  508 ,  618 , and  622  of previous displayed web browsing user interfaces  502 ,  616 , and  620 , respectively, as illustrated in  FIGS. 6M-6N . 
     In some embodiments, rather than requiring the deep press gesture to be on the backwards navigation control, the deep press gesture is made on an area of the touch-sensitive surface that corresponds to the left edge of the display or in an area of the touch-sensitive surface that corresponds to an area adjacent to the left edge of the display. In some embodiments, rather than requiring the deep press gesture to be on an area of the touch-sensitive surface that corresponds to the backwards navigation control, the deep press gesture is made anywhere on the touch-sensitive surface. In some embodiments, the gesture by the first contact is made with the flat portion of a thumb. 
     In response to detecting the gesture by the first contact on the touch-sensitive surface at a location that corresponds to the backwards navigation control ( 1506 ): in accordance with a determination that the gesture by the first contact is a gesture (e.g., a tap gesture) with an intensity of the first contact that does not meet the one or more predetermined intensity criteria (e.g., the intensity of the first contact during the gesture remains below the predetermined threshold intensity), the device replaces display ( 1510 ) of the first user interface of the first application with display of the second user interface of the first application (e.g., without displaying other user interfaces in the first application besides the second user interface). For example, device  100  determines that contact  624  does not include an intensity satisfying a deep press intensity threshold, and in response, displays user interface  616 , corresponding to a web browsing user interface displayed prior to display of web browsing user interface  502 , as illustrated in  FIGS. 6O-6P . 
     In some embodiments, the second user interface representation corresponds ( 1512 ) to a user interface in the first application that was displayed just prior to the display of the first user interface of the first application. 
     In some embodiments, the user interfaces in the first application are arranged in a hierarchy, and the second user interface corresponds ( 1514 ) to a user interface in the hierarchy that is adjacent to and higher than the first user interface. 
     It should be understood that the particular order in which the operations in  FIG. 15A  have been described is merely exemplary and is not intended to indicate that the described order is the only order in which the operations could be performed. One of ordinary skill in the art would recognize various ways to reorder the operations described herein. Additionally, it should be noted that details of other processes described herein with respect to other methods described herein (e.g., methods  1000 ,  1100 ,  1200 ,  1300 ,  1400 ,  2400 , and  2500 ) are also applicable in an analogous manner to method  1500  described above with respect to  FIG. 15A . For example, the contacts, gestures, user interface objects, intensity thresholds, focus selectors, animations described above with reference to method optionally have one or more of the characteristics of the contacts, gestures, user interface objects, intensity thresholds, focus selectors, animations described herein with reference to other methods described herein (e.g., methods  1000 ,  1100 ,  1200 ,  1300 ,  1400 ,  2400 , and  2500 ). For brevity, these details are not repeated here. 
       FIGS. 24A-24F  illustrate a flow diagram of a method  2400  of navigating between user interfaces in accordance with some embodiments. The method  2400  is performed at an electronic device (e.g., device  300 ,  FIG. 3 , or portable multifunction device  100 ,  FIG. 1A ) with a display and a touch-sensitive surface. In some embodiments, the display is a touch-screen display and the touch-sensitive surface is on or integrated with the display. In some embodiments, the display is separate from the touch-sensitive surface. In some embodiments, the touch-sensitive surface is part of a track pad or a remote control device that is separate from the display. In some embodiments, the operations in method  2400  are performed by an electronic device configured for management, playback, and/or streaming (e.g., from an external server) of audio and/or visual files that is in communication with a remote control and a display (e.g., Apple TV from Apple Inc. of Cupertino, Calif.). Some operations in method  2400  are, optionally, combined and/or the order of some operations is, optionally, changed. 
     As described below, the method  2400  provides an intuitive way to navigate between user interfaces. The method reduces the cognitive burden on a user when navigating between user interfaces, thereby creating a more efficient human-machine interface. For battery-operated electronic devices, enabling a user to navigate between user interfaces faster and more efficiently conserves power and increases the time between battery charges. 
     The device displays ( 2402 ), on the display, a user interface for an application. The device detects ( 2404 ) an edge input that includes detecting a change in a characteristic intensity of a contact proximate to an edge of the touch-sensitive surface. In response to detecting the edge input: in accordance with a determination that the edge input meets system-gesture criteria, the device performs ( 2406 ) an operation that is independent of the application (e.g., detection of the system-gesture criteria overrides detection of the application-gesture criteria; e.g., the operation that is independent of the application is performed even when the application-gesture criteria is met simultaneously). The system-gesture criteria include intensity criteria. In some embodiments, the intensity criteria are met when the characteristic intensity of the contact is above a first intensity threshold (e.g., a light press “IT L ” threshold). The system-gesture criteria include a location criterion that is met when the intensity criteria for the contact are met while (a predetermined portion of) the contact is within a first region relative to the touch-sensitive surface (e.g., a region that may or may not include a portion of the touch-sensitive surface). The first region relative to the touch-sensitive surface is determined based on one or more characteristics of the contact. 
     In some embodiments, the change in the characteristic intensity of the contact proximate to the edge of the touch-sensitive surface is ( 2408 ) detected at a location that corresponds to a respective operation in the application. 
     In some embodiments, in response to detecting the edge input: in accordance with a determination that the edge input meets application-gesture criteria and does not meet the system-gesture criteria, the device performs ( 2410 ) the respective operation in the application instead of performing the operation that is independent of the application. In some embodiments, in accordance with a determination that the edge input does not meet the system-gesture criteria and does not meet the application-gesture criteria, the device forgoes performing the operation that is independent of the application and the respective operation in the application. 
     In some embodiments, the intensity criteria is ( 2412 ) met when: the (detected) characteristic intensity of the contact proximate to the edge of the touch-sensitive surface is above a first intensity threshold; and the (detected) characteristic intensity of the contact proximate to the edge of the touch-sensitive surface is below a second intensity threshold. In some embodiments, detection of an increase in the characteristic intensity of the input above the second intensity threshold invokes the multitasking UI without requiring movement of the contact. 
     In some embodiments, the first region relative to the touch-sensitive surface has ( 2414 ) first boundaries (e.g., a first size and location) when the contact proximate to the edge of the touch-sensitive surface has first spatial properties (e.g., is a large, oblong contact characteristic of a flat finger input) and second boundaries, different from the first boundaries (e.g., a second size and/or location) when the contact proximate to the edge of the touch-sensitive surface has second spatial properties (e.g., is a small, round contact characteristic of a fingertip input). In some embodiments, the size and/or location of the region changes dynamically with the size of the contact. In some embodiments, the contact is categorized and one of a plurality of regions of different size and/or shape is selected based on the category of the contact. 
     In some embodiments, detecting the edge input includes ( 2416 ): detecting a first portion of the contact on the touch-sensitive surface proximate to the edge of the touch-sensitive surface; and extrapolating, based on the first portion of the contact, a second portion of the contact proximate to the edge of the touch-sensitive surface that extends beyond the edge of the touch sensitive surface, where the location of the contact, for the purposes of satisfying the location criteria, is determined based on at least in part on the extrapolated second portion of the contact (e.g., determining a location of the second portion of the contact proximate to the edge of the touch-sensitive surface with a maximum distance from the edge of the touch-sensitive surface based on a projection of the location of the second portion of the contact) (e.g., the contact is projected to the left and the location determination is based on a left most portion of the contact). 
     In some embodiments, in accordance with a determination that the contact proximate to the edge of the touch-sensitive surface has first spatial properties, the first region relative to the touch-sensitive surface is ( 2418 ) located entirely off of the touch-sensitive surface (e.g., located in a region that starts outside of the touch-sensitive surface and extends away from the edge of the touch-sensitive surface at which the first portion of the first contact was detected, such that the determination of whether or not the contact is within the first region is based on the extrapolated second portion of the contact that extends beyond an edge of the touch-sensitive surface); and in accordance with a determination that the contact proximate to the edge of the touch-sensitive surface has second spatial properties, the first region relative to the touch-sensitive surface includes a first portion located on the touch-sensitive surface, proximate to the edge of the touch-sensitive surface, and a second portion located off of the touch-sensitive surface, extending away from the edge of the touch sensitive surface (e.g., located in a region that starts within the touch-sensitive surface but extends off of the touch-sensitive surface away from the edge of the touch-sensitive surface at which the first portion of the first contact was detected, such that the determination of whether or not the contact is within the first region can be based on either the extrapolated second portion of the contact that extends beyond an edge of the touch-sensitive surface or on a portion of the contact that is detected on the touch-sensitive surface (e.g., if the contact is detected entirely on the touch-sensitive surface)). 
     In some embodiments, in accordance with a determination that the contact proximate to the edge of the touch-sensitive surface has first spatial properties, the first region relative to the touch-sensitive surface is ( 2420 ) located entirely off of the touch-sensitive surface, extending away from a first boundary located at a fixed distance from the edge of the touch-sensitive surface (e.g., located in a region that starts outside of the touch-sensitive surface and extends away from the edge of the touch-sensitive surface at which the first portion of the first contact was detected, such that the determination of whether or not the contact is within the first region is based on the extrapolated second portion of the contact that extends beyond an edge of the touch-sensitive surface); and in accordance with a determination that the contact proximate to the edge of the touch-sensitive surface has second spatial properties, the first region relative to the touch-sensitive surface is located entirely off of the touch-sensitive surface, extending away from a second boundary located at a second fixed distance from the edge of the touch-sensitive surface, where the second fixed distance is shorter than the first fixed distance (e.g., the boundary corresponding to a flat finger input is closer to the edge of the touch-sensitive surface than the boundary corresponding to a fingertip input). 
     In some embodiments, in accordance with a determination that a portion (e.g., the second portion) of the contact proximate to the edge of the touch-sensitive surface extends beyond the edge of the touch-sensitive surface, the location of the contact is ( 2422 ) a location of the (second) portion of the contact that extends beyond the edge of the touch-sensitive surface farthest from the edge of the touch-sensitive surface, based on a projection of the location of the (second) portion of the contact that extends beyond the edge of the touch-sensitive surface (e.g., when the contact extends beyond the touch-sensitive surface, the location of the contact is defined as the point farthest from the edge.); and in accordance with a determination that no portion of the contact proximate to the edge of the touch-sensitive surface extends beyond the edge of the touch-sensitive surface, the location of the contact is a location of the contact closest to the edge of the touch-sensitive surface (e.g., when the contact is entirely on the touch-sensitive surface, the location of the contact is defined as the point closest to the edge. In some embodiments, the location of the contact is defined as an average location of multiple points on the leading (e.g., left) edge of the contact.). In some embodiments, the location of the contact is defined as a centroid of the contact. 
     In some embodiments, the one or more characteristics, upon which the first region relative to the touch-sensitive surface is based, include ( 2424 ) a size of the contact proximate to the edge of the touch-sensitive surface (e.g., a contact shape characteristic of a fingertip input invokes a more stringent activation region than a contact shape characteristic of a flat finger input). 
     In some embodiments, the size of the contact proximate to the edge of the touch-sensitive surface is ( 2426 ) based on one or more of: a measure of the capacitance of the contact, a shape of the contact, and an area of the contact (e.g., a flat thumb is indicated by a larger signal total which is a normalized sum of the capacitance of the contact (e.g., how solidly is contact being made with the touch-sensitive surface), a larger geomean radius √((major axis)2+(minor axis)2) (e.g., which indicates the area of the contact and is larger for more oblong contacts), and a larger minor radius (e.g., which indicates whether the finger is laying flat on the touch-sensitive surface or not)). 
     In some embodiments, a difference in the first boundaries of the first region and the second boundaries of the first region is ( 2428 ) greater near a central portion of the edge of the touch-sensitive surface and is smaller near a distal portion of the edge of the touch-sensitive surface (e.g., the distance between a boundary of the first region and a boundary of the second region decreases toward the corner of the touch-sensitive surface). In some embodiments, the first boundaries of the first region and the second boundaries of the first region coincide within a predetermined distance from the corner of the touch-sensitive surface. In some embodiments, when the contact proximate to the edge of the screen has second spatial properties: in accordance with a determination that the location of the contact is proximate to a corner of the touch-sensitive surface, the first region has a second size that is the same as the first size (e.g., the expanded activation region is not available at the corners of the touch-sensitive surface to avoid accidental activation by the user&#39;s palm when reaching across the device); and, in accordance with a determination that the location of the contact is not proximate to a corner of the touch-sensitive surface, the first region has a second size that is larger than the first size. 
     In some embodiments, the first region relative to the touch-sensitive surface has ( 2430 ) a first or second size (e.g., dependent upon the size of the contact) when the contact proximate to the edge of the touch-sensitive surface is moving at a speed above a first speed threshold (e.g., an input parameter detected above a given threshold includes input parameters that are detected at the given threshold (e.g., “above” means “at or above”)) and a third size when the contact proximate to the edge of the touch-sensitive surface is moving at a speed below the first speed threshold. In some embodiments, the touch must start within a first region (e.g., 5 mm) and the increase in the characteristic intensity above the intensity threshold must be detected while the contact is moving above the speed threshold and within a second region (e.g., 20 mm). In some embodiments (e.g., where the application associates the location with an edge swipe operation), if the contact does not meet the system gesture criteria, the device performs an application-specific operation (e.g., navigation within the application). 
     In some embodiments, the system-gesture criteria further include ( 2432 ) direction criteria specifying a predetermined direction of motion on the touch-sensitive surface, where the direction criteria is met when the contact proximate to the edge of the touch-sensitive surface moves in the predetermined direction on the touch-sensitive surface (e.g., more vertical movement than horizontal movement). 
     In some embodiments, after initiating performance of the operation that is independent of the application: the device detects ( 2434 ) movement, on the touch-sensitive surface, of the contact proximate to the edge of the touch-sensitive surface. In response to detecting the movement of the contact: in accordance with a determination that the movement of the contact is in the predetermined direction, the device continues performance of the operation that is independent of the application; and in accordance with a determination that the movement of the contact is in a direction other than the predetermined direction, the device terminates performance of the operation that is independent of the application. 
     In some embodiments, the system-gesture criteria further include ( 2436 ) a failure condition that prevents the system-gesture criteria from being met when the contact proximate to the edge of the touch-sensitive surface moves outside of a second region (e.g., more than  20  mm away from the edge) relative to the touch-sensitive surface (e.g., on the touch-sensitive surface) before the system-gesture criteria are met (e.g., the system-gesture criteria cannot be met even if the contact moves back within the region). For example, prior to initiating performance of the operation that is independent of the application: the device detects movement, on the touch-sensitive surface, of the contact proximate to the edge of the touch-sensitive surface; and, in response to detecting the movement of the contact, in accordance with a determination that the contact moved outside a second region relative to the touch sensitive surface, the device prevents the system-gesture criteria from being met (e.g., the device prevents performance of the operation that is independent of the application). While preventing the system gesture criteria from being met, the device detects termination of the input (e.g., including liftoff of the contact proximate to the edge of the touch-sensitive surface); and, in response to detecting termination of the input, the device ceases to prevent the system gesture-gesture criteria from being met. 
     In some embodiments, the system-gesture criteria include ( 2438 ) a requirement (e.g., an additional requirement) that the characteristic intensity of the contact proximate to the edge of the touch-sensitive surface increases from an intensity below an intensity threshold to an intensity at or above the intensity threshold while the contact is within the first region relative to the touch-sensitive surface (e.g., the system-gesture criteria are not met when the characteristic intensity of the contact is increased above the intensity threshold while the contact is outside of the first region and the contact is then moved into the first region without decreasing the characteristic intensity of the contact below the intensity threshold). 
     In some embodiments, the intensity criteria vary ( 2440 ) based on time (e.g., relative to first detection of the contact proximate to the edge of the touch-sensitive surface or detection of the change in intensity of the contact; e.g., 150 g addition to the intensity threshold for first 100 ms after touchdown). 
     In some embodiments, the operation that is independent of the application (e.g., the system operation) is ( 2442 ) an operation for navigation between applications of the electronic device (e.g., a multitasking operation; e.g., switching to a different/prior application or entering a multitasking user interface). 
     In some embodiments, the respective operation in the application is ( 2444 ) a key press operation (e.g., a character insertion operation for a keyboard, or a keyboard switching operation, or a shift key activation option). 
     In some embodiments, the respective operation in the application is ( 2446 ) a page switching operation (e.g., next page, previous page, etc.). 
     In some embodiments, the respective operation in the application is ( 2448 ) for navigation within a hierarchy associated with the application (e.g., between levels of an application (e.g., song v. playlist) or history of an application (e.g., back and forward within a web browsing history)). 
     In some embodiments, the respective operation in the application is ( 2450 ) a preview operation (e.g., peek and pop for a link or row in a list). 
     In some embodiments, the respective operation in the application is ( 2452 ) a menu display operation (e.g., quick action or contact menu). 
     It should be understood that the particular order in which the operations in  FIGS. 24A-24F  have been described is merely exemplary and is not intended to indicate that the described order is the only order in which the operations could be performed. One of ordinary skill in the art would recognize various ways to reorder the operations described herein. Additionally, it should be noted that details of other processes described herein with respect to other methods described herein (e.g., methods  1000 ,  1100 ,  1200 ,  1300 ,  1400 ,  1500 , and  2500 ) are also applicable in an analogous manner to method  2400  described above with respect to  FIGS. 24A-24F . For example, the contacts, gestures, user interface objects, intensity thresholds, focus selectors, animations described above with reference to method optionally have one or more of the characteristics of the contacts, gestures, user interface objects, intensity thresholds, focus selectors, animations described herein with reference to other methods described herein (e.g., methods  1000 ,  1100 ,  1200 ,  1300 ,  1400 ,  1500 , and  2500 ). For brevity, these details are not repeated here. 
       FIGS. 25A-25H  illustrate a flow diagram of a method  2500  of navigating between user interfaces in accordance with some embodiments. The method  2500  is performed at an electronic device (e.g., device  300 ,  FIG. 3 , or portable multifunction device  100 ,  FIG. 1A ) with a display and a touch-sensitive surface. In some embodiments, the display is a touch-screen display and the touch-sensitive surface is on or integrated with the display. In some embodiments, the display is separate from the touch-sensitive surface. In some embodiments, the touch-sensitive surface is part of a track pad or a remote control device that is separate from the display. In some embodiments, the operations in method  2500  are performed by an electronic device configured for management, playback, and/or streaming (e.g., from an external server) of audio and/or visual files that is in communication with a remote control and a display (e.g., Apple TV from Apple Inc. of Cupertino, Calif.). Some operations in method  2500  are, optionally, combined and/or the order of some operations is, optionally, changed. 
     As described below, the method  2500  provides an intuitive way to navigate between user interfaces. The method reduces the cognitive burden on a user when navigating between user interfaces, thereby creating a more efficient human-machine interface. For battery-operated electronic devices, enabling a user to navigate between user interfaces faster and more efficiently conserves power and increases the time between battery charges. 
     The device displays ( 2502 ), on the display, a first view of a first application. While displaying the first view, the device detects ( 2504 ) a first portion of a first input that includes detecting a first contact on the touch-sensitive surface. In response to detecting the first portion of the first input, in accordance with a determination that the first portion of the first input meets application-switching criteria (e.g., including intensity criteria (e.g., “peek” intensity) and a location criterion (e.g., proximate to the edge of the touch sensitive surface) or an intensity-based edge swipe heuristic such as that described above with reference to method  2400 ), the device concurrently displays ( 2506 ), on the display, portions of a plurality of application views including the first application view and a second application view (and, optionally, ceasing to display another portion of the first application view (e.g., by sliding a portion of the first application view off of the display)). While concurrently displaying the portions of the plurality of application views, the device detects ( 2508 ) a second portion of the first input that includes liftoff of the first contact. In response to detecting the second portion of the first input that includes liftoff of the first contact: in accordance with a determination that the second portion of the first input meets first-view display criteria, where the first-view display criteria include a criterion that is met when the liftoff of the first contact is detected in a first region of the touch-sensitive surface (e.g., the portion proximate to the left edge of the touch sensitive surface), the device ceases ( 2510 ) to display the portion of the second application view and displays the (entire) first application view on the display; and in accordance with a determination that the second portion of the first input meets multi-view display criteria, where the multi-view display criteria includes a criterion that is met when the liftoff of the first contact is detected in a second region of the touch-sensitive surface that is different from the first region of the touch-sensitive surface (e.g., the middle portion of the touch sensitive surface), the device maintains concurrent display of at least a portion of the first application view and at least a portion of the second application view on the display after detecting the liftoff of the first contact. 
     In some embodiments, in response to detecting the second portion of the first input that includes liftoff of the first contact: in accordance with a determination that the second portion of the first input meets second-view display criteria, where the second-view display criteria includes a criterion that is met when the liftoff of the first contact is detected in a third region of the touch-sensitive surface that is different from the first region of the touch-sensitive surface and the second region of the touch-sensitive surface (e.g., the portion proximate to the right edge of the touch sensitive surface), the device ceases ( 2512 ) to display the first application view and displays the (entire) second application view on the display. 
     In some embodiments, after detecting the first portion of the first input that includes detecting the first contact on the touch-sensitive surface, and before detecting the second portion of the first input that includes liftoff of the first contact: the device detects ( 2514 ) movement of the first contact on the touch-sensitive surface. In response to detecting the movement of the first contact, in accordance with a determination that the first contact moves into the second region of the touch-sensitive surface, the device decreases respective sizes of the plurality of application views including the first application view and the second application view. In some embodiments, the sizes of the application views are decreased dynamically with continued movement of the contact across the second region of the touch-sensitive surface (e.g., there is a correlation between how far across the second region the contact has traveled and the size of the application views). In some embodiments, decreasing the size of the application views when the contact is in the second region of the touch-sensitive surface indicates to the user that lift-off of the contact in the second region will invoke the multitasking user interface. In some embodiments, the portion of the second application view contracts and moves in a direction of the movement of the contact in the second region (e.g., simulating dynamic contraction and sliding of the application “card” away from the “stack”). In some embodiments, a distance between two or more of the application views changes depending on movement of the first contact (e.g., application views other than the top application view move apart in addition to decreasing in size as the first contact moves across the display. 
     In some embodiments, while decreasing respective sizes of the plurality of application views including the first application view and the second application view: the device detects ( 2516 ) continued movement of the first contact on the touch-sensitive surface. In response to detecting the continued movement of the first contact, in accordance with a determination that the first contact moves into the third region of the touch-sensitive surface, the device increases respective sizes of the plurality of application views including the first application view and the second application view. In some embodiments, the sizes of the application views are increased dynamically with continued movement of the contact across the third region of the touch-sensitive surface (e.g., there is a correlation between how far across the third region the contact has traveled and the size of the application views). In some embodiments, increasing the size of the application views when the contact is in the third region of the touch-sensitive surface indicates to the user that lift-off of the contact in the third region will activate the application associated with the second application view (e.g., switch to the previous application). In some embodiments, the portion of the second application view expands and moves in a direction opposite movement of the contact in the third region (e.g., simulating dynamic expansion of the second application view into the user interface for the second application). In some embodiments, a distance between two or more of the application views changes depending on movement of the first contact (e.g., application views other than the top application view move together in addition to increasing in size as the first contact continues to move across the display. 
     In some embodiments, after detecting the first portion of the first input that includes detecting a first contact on the touch-sensitive surface, and before detecting the second portion of the first input that includes liftoff of the first contact: the device detects ( 2518 ) movement of the first contact on the touch-sensitive surface. In response to detecting the movement of the first contact, in accordance with a determination that the first contact crosses a boundary between two respective regions on the touch-sensitive surface, the device provides a tactile output. In some embodiments, the device provides haptic feedback when the contact moves into the third region of the touch-sensitive surface from the second region of the touch-sensitive region, but not when the contact moves back from the third region to the second region. 
     In some embodiments, display of respective portions of the plurality of application views are ( 2520 ) partially overlapping, including that the displayed portion of the first application view partially overlaps the displayed portion of the second application view. 
     In some embodiments, the first application view and the second application view are ( 2522 ) views of the same application (e.g., web page tabs). 
     In some embodiments, the first application view is ( 2524 ) a view of a first application and the second application view is a view of a second application that is different from the first application. 
     In some embodiments, in accordance with a determination that the second portion of the first input meets multi-view display criteria, where the multi-view display criteria include a criterion that is met when the liftoff of the first contact is detected in a second region of the touch-sensitive surface that is different from the first region of the touch-sensitive surface, maintaining concurrent display of at least a portion of the first application view and at least a portion of the second application view on the display includes ( 2526 ): entering a user interface selection mode; and displaying a plurality of user interface representations in a stack on the display, including the at least a portion of the first application view and at least a portion of the second application view, where: at least a first user interface representation, corresponding to the at least a portion of the second application view, and at least a second user interface representation, corresponding to the at least a portion of the first application view and disposed above the first user interface representation in the stack, are visible on the display, the second user interface representation is offset from the first user interface representation in a first direction (e.g., laterally offset to the right on the display), and the second user interface representation partially exposes the first user interface representation. In some embodiments, representations in the stack are partially spread out in one direction on the display (e.g., to the right, as shown in  FIGS. 5P and 22C ). In some embodiments, at a given time, information (e.g., an icon, title, and content for the corresponding user interface) for a predetermined number of the representations (e.g., 2, 3, 4, or 5 representations) in the stack is visible, while the rest of the representations in the stack are either off-screen or are beneath the representations that include visible information. In some embodiments, the representations that are beneath the representations that include visible information are stacked together so closely that no information is displayed for these representations. In some embodiments, the representations that are beneath the representations that include visible information are stylistic representations, such as just generic edges  503 , as shown in  FIG. 5P . 
     In some embodiments, while in the user interface selection mode: the device detects ( 2528 ) a second input including a drag gesture by a second contact at a location on the touch-sensitive surface that corresponds to a location of the first user interface representation on the display, the second contact moving across the touch-sensitive surface in a direction that corresponds to the first direction on the display; and, while the second contact is at a location on the touch-sensitive surface that corresponds to the location of the first user interface representation on the display and moving across the touch-sensitive surface in a direction that corresponds to the first direction on the display: the device moves the first user interface representation in the first direction on the display at a first speed in accordance with a speed of the second contact on the touch-sensitive surface; and the device moves the second user interface representation, disposed above the first user interface representation, in the first direction at a second speed greater than the first speed. For example, with respect to moving the first user interface representation, on a touch-sensitive display, the card or other representation under the finger contact moves with the same speed as the finger contact; and on a display coupled to a track pad, the card or other representation at the location corresponding to the location of the contact moves at an onscreen speed that corresponds to (or is based on) the speed of the finger contact on the track pad. In some embodiments, a focus selector is shown on the display to indicate the onscreen location that corresponds to the location of the contact on the touch-sensitive surface. In some embodiments, the focus selector may be represented by a cursor, a movable icon, or visual differentiators that separate an onscreen object (e.g., a user interface representation) from its peers that do not have the focus. In another example, with respect to moving the second user interface representation, in some embodiments, the first direction is rightward. In some embodiments, the first speed is the same speed as the current speed of the contact. In some embodiments, the movement of the first user interface representation creates a visual effect that the finger contact is grabbing and dragging the first user interface representation. At the same time, the second user interface representation is moving faster than the first user interface representation. This faster movement of the second user interface representation creates the visual effect that as the second user interface representation moves in the first direction towards the edge of the display, an increasingly larger portion of the first user interface representation is revealed from underneath the second user interface representation. In combination, these two concurrent movements enable a user to see more of the first user interface representation before deciding whether to select and display the corresponding first user interface. 
     In some embodiments, while in the user interface selection mode, including display of at least two of the plurality of user interface representations in the stack, the device detects ( 2530 ) a selection input (e.g., a tap gesture at a location on the touch-sensitive surface that corresponds to a location on a user interface representation) directed to one of the at least two user interface representations in the stack. In response to detecting the selection input: the device ceases to display the stack, and displays a user interface that corresponds to the selected one of the at least two user interface representations. In some embodiments, the user interface that corresponds to the selected user interface representation is displayed without displaying any user interfaces that correspond to other user interface representations in the stack. In some embodiments, the display of the user interface that corresponds to the selected user interface representation replaces the display of the stack. 
     In some embodiments, while displaying, in the stack, at least the first user interface representation and the second user interface representation above the first user interface representation: the device detects ( 2532 ) a deletion input directed to the first user interface representation (e.g., an upward drag gesture at a location on the touch-sensitive surface that corresponds to a location on the first user interface representation). In response to detecting the deletion input directed to the first user interface representation: the device removes the first user interface representation from a first position in the stack. In some embodiments, when swiping to close, the adjacent application views move together in z space (e.g., the application views behind the application view that is being manipulated moves toward the current application view). If movement is in the opposite direction, the adjacent application views move away from each other in z space (e.g., the application views behind the application view that is being manipulated moves away the current application view). 
     In some embodiments, entering a user interface selection mode includes ( 2534 ): animating a decrease in size of the first application view when transitioning into the second user interface representation; and animating a decrease in size of the second application view when transitioning into the first user interface representation. For example, in the “peek” stage, the UI cards are referred to as application views and in the “pop” stage (e.g., multitasking user interface), the UI cards are referred to as user interface representations. In some embodiments, the device indicates to the user that it has entered into the multitasking user interface by reducing the size of the application views (e.g., which become user interface representations). 
     In some embodiments, the application-switching criteria include ( 2536 ) intensity criteria. In some embodiments, the intensity criteria are met when the characteristic intensity of the contact is above a first intensity threshold. In some embodiments, the system-gesture criteria include a location criterion that is met when the intensity criteria for the contact are met while the contact is within a first region relative to the touch-sensitive surface (e.g., a region that may or may not include a portion of the touch-sensitive surface, such as those described above with reference to method  2400 ). 
     In some embodiments, the size of the first region relative to the touch-sensitive surface is ( 2538 ) determined based on one or more characteristics of the contact. In some embodiments, the first region relative to the touch-sensitive surface has a first size when the contact proximate to the edge of the touch-sensitive surface has first spatial properties (e.g., is a large, oblong contact characteristic of a flat finger input) and a second size when the contact proximate to the edge of the touch-sensitive surface has second spatial properties (e.g., is a small, round contact characteristic of a fingertip input). In some embodiments, the size of the region changes dynamically with the size of the contact. In some embodiments, the contact is categorized and one of a plurality of discretely sized regions is selected. 
     In some embodiments, the intensity criteria of the application-switching criteria are ( 2540 ) met when: the (detected) characteristic intensity of the first contact is above a first intensity threshold (e.g., a peek/preview intensity threshold); and the (detected) characteristic intensity of the first contact is below a second intensity threshold (e.g., a pop/commit intensity threshold). 
     In some embodiments, in response to detecting the first portion of the first input, in accordance with a determination that the first portion of the first input meets the application-switching criteria, the device provides ( 2542 ) tactile output. 
     In some embodiments, in response to detecting the first portion of the first input, in accordance with a determination that the first portion of the first input meets preview criteria: the device moves ( 2544 ) the first view of the first application partially off of the display (e.g., sliding the active user interface to the right with or without decreasing the size of the user interface) and displays a portion of the second application view at a location of the display from which the first view of the first application was displaced (e.g., the active user interface slides over, revealing the edge of the previously active user interface from under the currently active user interface). 
     In some embodiments, the preview criteria includes ( 2546 ): a location criterion that is met while the contact is within the first region relative to the touch-sensitive surface, and an intensity criteria that is met when the characteristic intensity of the contact is above a preview intensity threshold (e.g., “hint” intensity) and below an application-switching intensity threshold (e.g., “peek” intensity/first intensity threshold). 
     In some embodiments, the application-switching criteria include ( 2548 ) a criterion that is met when an intensity of the first contact increases above a first intensity threshold (e.g., a peek/preview intensity threshold); maintaining concurrent display of at least a portion of the first application view and at least a portion of the second application view on the display after detecting the liftoff of the first contact includes displaying a multitasking user interface; and in response to detecting the first portion of the first input, in accordance with a determination that the first portion of the first input meets multitasking criteria that include a criterion that is met when an intensity of the first contact increases above a second intensity threshold that is greater than the first intensity threshold, the device displays the multitasking user interface. For example, the multitasking user interface can either be displayed by meeting the application-switching criteria, which can be met with a contact having an intensity above the first intensity threshold and below the second intensity threshold and then moving the contact across the touch-sensitive surface to a location that corresponds to a middle portion of the display, or by meeting the multitasking criteria which can be met with a contact having an intensity above the second intensity threshold. 
     In some embodiments, in response to detecting the first portion of the first input, in accordance with a determination that the first portion of the first input meets multitasking criteria (e.g., including high intensity criteria (e.g., “pop” intensity) and optionally a location criterion (e.g., proximate to the edge of the touch sensitive surface, in the first region, or in the second region)): the device enters ( 2550 ) a user interface selection mode, and displays a plurality of user interface representation in a stack on the display, including the at least a portion of the first application view and at least a portion of the second application view. In some embodiments, at least a first user interface representation, corresponding to the at least a portion of the second application view, and at least a second user interface representation, corresponding to the at least a portion of the first application view and disposed above the first user interface representation in the stack, are visible on the display, the second user interface representation is offset from the first user interface representation in a first direction (e.g., laterally offset to the right on the display), and the second user interface representation partially exposes the first user interface representation. In some embodiments, representations in the stack are partially spread out in one direction on the display (e.g., to the right, as shown in  FIGS. 5P and 23G ). In some embodiments, at a given time, information (e.g., an icon, title, and content for the corresponding user interface) for a predetermined number of the representations (e.g., 2, 3, 4, or 5 representations) in the stack is visible, while the rest of the representations in the stack are either off-screen or are beneath the representations that include visible information. In some embodiments, the representations that are beneath the representations that include visible information are stacked together so closely that no information is displayed for these representations. In some embodiments, the representations that are beneath the representations that include visible information are stylistic representations, such as just generic edges  503 , as shown in  FIG. 5E . 
     In some embodiments, the multitasking criteria include ( 2552 ) intensity criteria that are met when the (detected) characteristic intensity of the first contact is above the second intensity threshold. 
     In some embodiments, the multitasking criteria include ( 2554 ) a location criterion that is met when the multitasking intensity criteria are met while the contact is within the first region of the touch-sensitive surface. 
     It should be understood that the particular order in which the operations in  FIGS. 25A-25H  have been described is merely exemplary and is not intended to indicate that the described order is the only order in which the operations could be performed. One of ordinary skill in the art would recognize various ways to reorder the operations described herein. Additionally, it should be noted that details of other processes described herein with respect to other methods described herein (e.g., methods  1000 ,  1100 ,  1200 ,  1300 ,  1400 ,  1500 , and  2400 ) are also applicable in an analogous manner to method  2500  described above with respect to  FIGS. 25A-25H . For example, the contacts, gestures, user interface objects, intensity thresholds, focus selectors, animations described above with reference to method optionally have one or more of the characteristics of the contacts, gestures, user interface objects, intensity thresholds, focus selectors, animations described herein with reference to other methods described herein (e.g., methods  1000 ,  1100 ,  1200 ,  1300 ,  1400 ,  1500 , and  2400 ). For brevity, these details are not repeated here. 
     In accordance with some embodiments,  FIG. 16  shows a functional block diagram of an electronic device  1600  configured in accordance with the principles of the various described embodiments. The functional blocks of the device are, optionally, implemented by hardware, software, or a combination of hardware and software to carry out the principles of the various described embodiments. It is understood by persons of skill in the art that the functional blocks described in  FIG. 16  are, optionally, combined or separated into sub-blocks to implement the principles of the various described embodiments. Therefore, the description herein optionally supports any possible combination or separation or further definition of the functional blocks described herein. 
     As shown in  FIG. 16 , an electronic device  1600  includes a display unit  1602  configured to display a user interface, a touch-sensitive surface unit  1604  configured to receive contacts, optionally one or more sensor units  1606  configured to detect intensity of contacts with the touch-sensitive surface unit  1604 ; and a processing unit  1608  coupled with the display unit  1602 , the touch-sensitive surface unit  1604  and the optional one or more sensor units  1606 . In some embodiments, the processing unit  1608  includes: a display enabling unit  1610 , a detecting unit  1612 , a moving unit  1614 , an entering unit  1616 , a revealing unit  618 , a determining unit, an applying unit  520 , an inserting unit  1624 , and a removing unit  1626 . 
     The processing unit  1610  is configured to: enable display of a plurality of user interface representations in a stack on the display unit  1602  (e.g., with the display enabling unit  1610 ), wherein: at least a first user interface representation and a second user interface representation disposed above the first user interface representation in the stack, are visible on the display unit  1602 , the second user interface representation is offset from the first user interface representation in a first direction, and the second user interface representation partially exposes the first user interface representation; detect a first drag gesture by a first contact at a location on the touch-sensitive surface unit  1604  that corresponds to a location of the first user interface representation on the display unit  1602  (e.g., with detecting unit  1612 ), the first contact moving across the touch-sensitive surface unit  1604  in a direction that corresponds to the first direction on the display unit  1602 ; and, while the first contact is at a location on the touch-sensitive surface unit  1604  that corresponds to the location of the first user interface representation on the display unit  1602  and moving across the touch-sensitive surface unit  1604  in a direction that corresponds to the first direction on the display unit: move the first user interface representation in the first direction on the display unit  1602  at a first speed in accordance with a speed of the first contact on the touch-sensitive surface unit  1604  (e.g., with the moving unit  1604 ); and move the second user interface representation, disposed above the first user interface representation, in the first direction at a second speed greater than the first speed (e.g., with the moving unit  1614 ). 
     In accordance with some embodiments,  FIG. 17  shows a functional block diagram of an electronic device  1700  configured in accordance with the principles of the various described embodiments. The functional blocks of the device are, optionally, implemented by hardware, software, or a combination of hardware and software to carry out the principles of the various described embodiments. It is understood by persons of skill in the art that the functional blocks described in  FIG. 17  are, optionally, combined or separated into sub-blocks to implement the principles of the various described embodiments. Therefore, the description herein optionally supports any possible combination or separation or further definition of the functional blocks described herein. 
     As shown in  FIG. 17 , an electronic device  1700  includes a display unit  1702  configured to display a user interface, a touch-sensitive surface unit  1704  configured to receive contacts, one or more sensor units  1706  configured to detect intensity of contacts with the touch-sensitive surface unit  1704 ; and a processing unit  1708  coupled with the display unit  1702 , the touch-sensitive surface unit  1704  and the one or more sensor units  1706 . In some embodiments, the processing unit  1708  includes: a display enabling unit  1710 , a detecting unit  1712 , a moving unit  1714 , an entering unit  1716 , and an operation performing unit  1718 . 
     The processing unit  1710  is configured to: enable display a first user interface on the display unit  1702  (e.g., with display enabling unit  1710 ); while displaying the first user interface on the display unit  1702 , detect an input by a first contact on the touch-sensitive surface unit  1704  (e.g., with detecting unit  1712 ); while detecting the input by the first contact, enable display of a first user interface representation and at least a second user interface representation on the display unit  1702  (e.g., with the display enabling unit  1710 ); while displaying the first user interface representation and at least the second user interface representation on the display unit  1702 , detect termination of the input by the first contact (e.g., with the detecting unit  1712 ); and, in response to detecting termination of the input by the first contact: in accordance with a determination that the first contact had a characteristic intensity during the input that was below a predetermined intensity threshold and the first contact moved during the input in a direction across the touch-sensitive surface  1704  that corresponds to a predefined direction on the display  1702 , enable display of a second user interface that corresponds to the second user interface representation (e.g., with the display enabling unit  1710 ); and in accordance with a determination that the first contact had a characteristic intensity during the input that was below the predetermined intensity threshold and the first contact did not move during the input in a direction across the touch-sensitive surface unit  1704  that corresponds to the predefined direction on the display unit  1702 , enable redisplay of the first user interface (e.g., with display enabling unit  1710 ). 
     In accordance with some embodiments,  FIG. 18  shows a functional block diagram of an electronic device  1800  configured in accordance with the principles of the various described embodiments. The functional blocks of the device are, optionally, implemented by hardware, software, or a combination of hardware and software to carry out the principles of the various described embodiments. It is understood by persons of skill in the art that the functional blocks described in  FIG. 18  are, optionally, combined or separated into sub-blocks to implement the principles of the various described embodiments. Therefore, the description herein optionally supports any possible combination or separation or further definition of the functional blocks described herein. 
     As shown in  FIG. 18 , an electronic device  1800  includes a display unit  1802  configured to display a user interface, a touch-sensitive surface unit  1804  configured to receive contacts, one or more sensor units  1806  configured to detect intensity of contacts with the touch-sensitive surface unit  1804 ; and a processing unit  1808  coupled with the display unit  1802 , the touch-sensitive surface unit  1804  and the one or more sensor units  1806 . In some embodiments, the processing unit  1808  includes: a display enabling unit  1810 , a detecting unit  1812 , a moving unit  1814 , an increasing unit  1816 , a changing unit  1818 , and a varying unit  1820 . 
     The processing unit  1808  is configured to: enable display of a first user interface on the display unit (e.g., with display enabling unit  1810 ; while enabling display of the first user interface on the display unit, detect, on the touch-sensitive surface unit  1804 , an input by a first contact that includes a period of increasing intensity of the first contact (e.g., with the detecting unit  1812 ); in response to detecting the input by the first contact that includes the period of increasing intensity of the first contact: enable display of a first user interface representation for the first user interface and a second user interface representation for a second user interface on the display unit  1802  (e.g., with the display enabling unit  1810 ), wherein the first user interface representation is displayed over the second user interface representation and partially exposes the second user interface representation; while enabling display of the first user interface representation and the second user interface representation on the display unit  1802 , detect that, during the period of increasing intensity of the first contact, the intensity of the first contact meets one or more predetermined intensity criteria (e.g., with the detecting unit  1812 ); in response to detecting that the intensity of the first contact meets the one or more predetermined intensity criteria: cease to enable display of the first user interface representation and the second user interface representation on the display unit  1802  (e.g., with the display enabling unit  1810 ); and enable display of the second user interface on the display unit  1802  (e.g., with display enabling unit  1810 ). 
     In accordance with some embodiments,  FIG. 19  shows a functional block diagram of an electronic device  1900  configured in accordance with the principles of the various described embodiments. The functional blocks of the device are, optionally, implemented by hardware, software, or a combination of hardware and software to carry out the principles of the various described embodiments. It is understood by persons of skill in the art that the functional blocks described in  FIG. 19  are, optionally, combined or separated into sub-blocks to implement the principles of the various described embodiments. Therefore, the description herein optionally supports any possible combination or separation or further definition of the functional blocks described herein. 
     As shown in  FIG. 19 , an electronic device  1900  includes a display unit  1902  configured to display a user interface, a touch-sensitive surface unit  1904  configured to receive contacts, one or more sensor units  1906  configured to detect intensity of contacts with the touch-sensitive surface unit  1904 ; and a processing unit  1908  coupled with the display unit  1902 , the touch-sensitive surface unit  1904  and the one or more sensor units  1906 . In some embodiments, the processing unit  1908  includes: a display enabling unit  1910 , a detecting unit  1912 , a moving unit  1914 , an increasing unit  1916 , a decreasing unit  1918 , and an entering unit  1920 . 
     The processing unit  1910  is configured to: enable display of a plurality of user interface representations in a stack on the display unit  1902  (e.g., with the display enabling unit  1910 ), wherein: at least a first user interface representation, a second user interface representation, and a third user interface representation are visible on the display unit  1902 , the first user interface representation is laterally offset from the second user interface representation in a first direction and partially exposes the second user interface representation, and the second user interface representation is laterally offset from the third user interface representation in the first direction and partially exposes the third user interface representation; detect an input by a first contact on the touch-sensitive surface unit  1904  at a location that corresponds to the second user interface representation on the display unit  1902  (e.g., with detecting unit  1922 ); and, in accordance with detecting an increase in intensity of the first contact on the touch-sensitive surface unit  1904  at the location that corresponds to the second user interface representation on the display unit  1902  (e.g., with the detecting unit  1912 ), increase an area of the second user interface representation that is exposed from behind the first user interface representation by increasing the lateral offset between the first user interface representation and the second user interface representation (e.g., with the increasing unit  1916 ). 
     In accordance with some embodiments,  FIG. 20  shows a functional block diagram of an electronic device  2000  configured in accordance with the principles of the various described embodiments. The functional blocks of the device are, optionally, implemented by hardware, software, or a combination of hardware and software to carry out the principles of the various described embodiments. It is understood by persons of skill in the art that the functional blocks described in  FIG. 20  are, optionally, combined or separated into sub-blocks to implement the principles of the various described embodiments. Therefore, the description herein optionally supports any possible combination or separation or further definition of the functional blocks described herein. 
     As shown in  FIG. 20 , an electronic device  2000  includes a display unit  2002  configured to display a user interface, a touch-sensitive surface unit  2004  configured to receive contacts, optionally one or more sensor units  2006  configured to detect intensity of contacts with the touch-sensitive surface unit  2004 ; and a processing unit  2008  coupled with the display unit  2002 , the touch-sensitive surface unit  2004  and the optional one or more sensor units  2006 . In some embodiments, the processing unit  2008  includes: a display enabling unit  2010 , a detecting unit  2012 , a moving unit  2014 , and a revealing unit  2016 . 
     The processing unit  2010  is configured to: enable display of a plurality of user interface representations in a stack on the display unit  2002  (e.g., with the display enabling unit  2010 ), wherein: at least a first user interface representation, a second user interface representation, and a third user interface representation are visible on the display unit  2002 , the second user interface representation is laterally offset from the first user interface representation in a first direction and partially exposes the first user interface representation, and the third user interface representation is laterally offset from the second user interface representation in the first direction and partially exposes the second user interface representation; detect a drag gesture by a first contact that moves across the touch-sensitive surface unit  2004  (e.g., with the detecting unit  2012 ), wherein movement of the drag gesture by the first contact corresponds to movement across one or more of the plurality of user interface representations in the stack; and, during the drag gesture, when the first contact moves over a location on the touch-sensitive surface unit  2004  that corresponds to the first user interface representation on the display unit  2002 , reveal more of the first user interface representation from behind the second user interface representation on the display unit (e.g., with the revealing unit  2016 ). 
     In accordance with some embodiments,  FIG. 21  shows a functional block diagram of an electronic device  2100  configured in accordance with the principles of the various described embodiments. The functional blocks of the device are, optionally, implemented by hardware, software, or a combination of hardware and software to carry out the principles of the various described embodiments. It is understood by persons of skill in the art that the functional blocks described in  FIG. 21  are, optionally, combined or separated into sub-blocks to implement the principles of the various described embodiments. Therefore, the description herein optionally supports any possible combination or separation or further definition of the functional blocks described herein. 
     As shown in  FIG. 21 , an electronic device  2100  includes a display unit  1602  configured to display a user interface, a touch-sensitive surface unit  2104  configured to receive contacts, one or more sensor units  2106  configured to detect intensity of contacts with the touch-sensitive surface unit  2104 ; and a processing unit  2108  coupled with the display unit  2102 , the touch-sensitive surface unit  2104  and the one or more sensor units  2106 . In some embodiments, the processing unit  2108  includes: a display enabling unit  2110  and a detecting unit  2112 . 
     The processing unit  2110  is configured to: enable display of a first user interface of a first application on the display unit  2102  (e.g., with the display enabling unit  2110 ), the first user interface including a backwards navigation control; while displaying the first user interface of the first application on the display unit  2102 , detect a gesture by a first contact on the touch-sensitive surface unit  2104  at a location that corresponds to the backwards navigation control on the display unit  2102  (e.g., with the detecting unit  2112 ; in response to detecting the gesture by the first contact on the touch-sensitive surface unit  2104  at a location that corresponds to the backwards navigation control: in accordance with a determination that the gesture by the first contact is a gesture with an intensity of the first contact that meets one or more predetermined intensity criteria, replace display of the first user interface of the first application with display of a plurality of representations of user interfaces of the first application (e.g., with the display enabling unit  2110 ), including a representation of the first user interface and a representation of a second user interface; and, in accordance with a determination that the gesture by the first contact is a gesture with an intensity of the first contact that does not meet the one or more predetermined intensity criteria, replace display of the first user interface of the first application with display of the second user interface of the first application (e.g., using display enabling unit  2110 ). 
     In accordance with some embodiments,  FIG. 26  shows a functional block diagram of an electronic device  2600  configured in accordance with the principles of the various described embodiments. The functional blocks of the device are, optionally, implemented by hardware, software, or a combination of hardware and software to carry out the principles of the various described embodiments. It is understood by persons of skill in the art that the functional blocks described in  FIG. 26  are, optionally, combined or separated into sub-blocks to implement the principles of the various described embodiments. Therefore, the description herein optionally supports any possible combination or separation or further definition of the functional blocks described herein. 
     As shown in  FIG. 26 , an electronic device includes a display unit  2602  configured to display content items; a touch-sensitive surface unit  2604  configured to receive user inputs; one or more sensor units  2606  configured to detect intensity of contacts with the touch-sensitive surface unit  2604 ; and a processing unit  2608  coupled to the display unit  2602 , the touch-sensitive surface unit  2604  and the one or more sensor units  2606 . In some embodiments, the processing unit  2608  includes a display enabling unit  2610 , a detecting unit  2612 , and a determining unit  2614 . In some embodiments, the processing unit  7 $ 08  is configured to: enable display (e.g., with display enabling unit  2610 ), on the display unit (e.g., display unit  2602 ), of a user interface for an application; detect (e.g., with detecting unit  2612 ) an edge input that includes detecting a change in a characteristic intensity of a contact proximate to an edge of the touch-sensitive surface; and, in response to detecting the edge input: in accordance with a determination (e.g., with determining unit  2614 ) that the edge input meets system-gesture criteria, perform an operation that is independent of the application, where: the system-gesture criteria include intensity criteria; the system-gesture criteria include a location criterion that is met when the intensity criteria for the contact are met while the contact is within a first region relative to the touch-sensitive surface; and the first region relative to the touch-sensitive surface unit  2604  is determined based on one or more characteristics of the contact. 
     In accordance with some embodiments,  FIG. 27  shows a functional block diagram of an electronic device  2700  configured in accordance with the principles of the various described embodiments. The functional blocks of the device are, optionally, implemented by hardware, software, or a combination of hardware and software to carry out the principles of the various described embodiments. It is understood by persons of skill in the art that the functional blocks described in  FIG. 27  are, optionally, combined or separated into sub-blocks to implement the principles of the various described embodiments. Therefore, the description herein optionally supports any possible combination or separation or further definition of the functional blocks described herein. 
     As shown in  FIG. 27 , an electronic device includes a display unit  2702  configured to display content items; a touch-sensitive surface unit  2704  configured to receive user inputs; one or more sensor units  2706  configured to detect intensity of contacts with the touch-sensitive surface unit  2704 ; and a processing unit  2708  coupled to the display unit  2702 , the touch-sensitive surface unit  2704  and the one or more sensor units  2706 . In some embodiments, the processing unit  2708  includes a display enabling unit  2710 , a detecting unit  2712 , and a determining unit  9 $ 14 . In some embodiments, the processing unit  2708  is configured to: enable display (e.g., with display enabling unit  2710 ), on the display unit (e.g., display unit  2702 ), of a first view of a first application; while enabling display of the first view, detect (e.g., with detecting unit  2712 ) a first portion of a first input that includes detecting a first contact on the touch-sensitive surface unit  2704 ; in response to detecting the first portion of the first input, in accordance with a determination (e.g., with determining unit  2714 ) that the first portion of the first input meets application-switching criteria, enable concurrent display (e.g., with display enabling unit  2710 ), on the display unit, of portions of a plurality of application views including the first application view and a second application view; while enabling concurrent display of the portions of the plurality of application views, detect (e.g., with detecting unit  2712 ) a second portion of the first input that includes liftoff of the first contact; and in response to detecting the second portion of the first input that includes liftoff of the first contact: in accordance with a determination (e.g., with determining unit  2714 ) that the second portion of the first input meets first-view display criteria, where the first-view display criteria include a criterion that is met when the liftoff of the first contact is detected in a first region of the touch-sensitive surface unit  2704 , cease to enable display (e.g., with display enable unit  2710 ) of the portion of the second application view and enable display (e.g., with display enable unit  2710 ) of the first application view on the display unit; and in accordance with a determination (e.g., with determining unit  2714 ) that the second portion of the first input meets multi-view display criteria, where the multi-view display criteria includes a criterion that is met when the liftoff of the first contact is detected in a second region of the touch-sensitive surface unit  2704  that is different from the first region of the touch-sensitive surface unit  2704 , maintain concurrent display (e.g., with display enable unit  2710 ) of at least a portion of the first application view and at least a portion of the second application view on the display after detecting the liftoff of the first contact. 
     The operations in the information processing methods described above are, optionally implemented by running one or more functional modules in information processing apparatus such as general purpose processors (e.g., as described above with respect to  FIGS. 1A and 3 ) or application specific chips. 
     The operations described above with reference to  FIGS. 10A-10H, 11A-11E, 12A-12E, 13A-13D, 14A-14C, and 15  are, optionally, implemented by components depicted in  FIGS. 1A-1B  or  FIGS. 16-21 . For example, user interface entering operations  1006 ,  1110 , and  1312 , visual effect applying operations  1018 ,  1024 ,  1048 ,  1208 ,  1212 ,  1224 ,  1320 ,  1322 ,  1350 ,  1408 ,  1410 ,  1414 , and  1416 , detection operations  1030 ,  1052 ,  1062 ,  1080 ,  1084 ,  1091 ,  1092 ,  1096 ,  1104 ,  1116 ,  1126 ,  1130 ,  1138 ,  1142 ,  1146 ,  1204 ,  1210 ,  1220 ,  1232 ,  1236 ,  1244 ,  1248 ,  1308 ,  1318 ,  1328 ,  1340 ,  1346 ,  1350 ,  1404 ,  1418 ,  1426 , and  1504 , user interface representation insertion operation  1082 , user interface representation removal operation  1088 , user interface representation moving operations  1034 ,  1036 ,  1050 ,  1056 ,  1058 ,  1060 ,  1068 ,  1070 ,  1072 ,  1098 ,  1150 ,  1152 ,  1324 ,  1326 ,  1332 ,  1334 ,  1336 , and  1338 , and content-dependent execution operation  1140 , are, optionally, implemented by event sorter  170 , event recognizer  180 , and event handler  190 . Event monitor  171  in event sorter  170  detects a contact on touch-sensitive display  112 , and event dispatcher module  174  delivers the event information to application  136 - 1 . A respective event recognizer  180  of application  136 - 1  compares the event information to respective event definitions  186 , and determines whether a first contact at a first location on the touch-sensitive surface (or whether rotation of the device) corresponds to a predefined event or sub-event, such as selection of an object on a user interface, or rotation of the device from one orientation to another. When a respective predefined event or sub-event is detected, event recognizer  180  activates an event handler  190  associated with the detection of the event or sub-event. Event handler  190  optionally uses or calls data updater  176  or object updater  177  to update the application internal state  192 . In some embodiments, event handler  190  accesses a respective GUI updater  178  to update what is displayed by the application. Similarly, it would be clear to a person having ordinary skill in the art how other processes can be implemented based on the components depicted in  FIGS. 1A-1B . 
     The foregoing description, for purpose of explanation, has been described with reference to specific embodiments. However, the illustrative discussions above are not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations are possible in view of the above teachings. For example, the methods described herein are also applicable in an analogous manner to electronic devices configured for management, playback, and/or streaming (e.g., from an external server) of audio and/or visual content that are in communication with a remote control and a display (e.g., Apple TV from Apple Inc. of Cupertino, Calif.). For such devices, inputs are optionally received that correspond to gestures on a touch-sensitive surface of the remote control, voice inputs to the remote control, and/or activation of buttons on the remote control, rather than having the touch-sensitive surface, audio input device (e.g., a microphone), and/or buttons on the device itself. For such devices, data is optionally provided to the display rather than displayed by the device itself. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, to thereby enable others skilled in the art to best use the invention and various described embodiments with various modifications as are suited to the particular use contemplated.

Metadata:
Filing Date: 20160422
Publication Date: 20180313
Grant Date: 20180313
Priority Date: 20150607
Inventors: ALONSO RUIZ MARCOS
DASCOLA JONATHAN R.
FOSS CHRISTOPHER P.
KARUNAMUNI CHANAKA G.
CHAUDHRI IMRAN A.
Assignee: APPLE INC
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Family ID: 56109832