user: Describe Header from the Blender manual or Python API, including usage steps and snippets.

assistant: ### Display Mode

This header dropdown lets you choose what the Outliner should show.

Scenes:
:   Shows the [view layers](../../render/layers/introduction.xhtml),
    [collections](../../scene_layout/collections/introduction.xhtml),
    and objects across all scenes.

View Layer:
:   Shows the collections and objects in the current view layer of the current scene.

Video Sequencer:
:   Shows the images and videos that are used in the [Video Sequencer](../../video_editing/index.xhtml).

Blender File:
:   Lists all data in the current blend-file. On the right side of the list, a shield icon shows the number
    of users – clicking it adds or removes a [fake user](../../files/data_blocks.xhtml#data-system-datablock-fake-user).

Data API:
:   Lists every [data-block](../../files/data_blocks.xhtml) in the file along with any properties that it might have.

Library Overrides:
:   Shows the [library overrides](../../files/linked_libraries/library_overrides.xhtml).
    Separated further into two view modes:

    Properties:
    :   Shows the data-blocks that have overridden properties in a list grouped by type.
        You can expand each data-block to see and change these properties.

    Hierarchies:
    :   Shows the overridden data-blocks in a tree that visualizes their hierarchy.
        This includes parent data-blocks that were overridden implicitly.
        For example, if you created an override for a material,
        this tree would show the hierarchy object > mesh > material.

        This view also shows a column of icons on the right that let you toggle whether
        each override is editable.

Unused Data:
:   Lists the data-blocks that are unused or only have a [fake user](../../files/data_blocks.xhtml#data-system-datablock-fake-user).
    You can add/remove a fake user by clicking the shield icon on the right.

    Unused data-blocks are automatically deleted when saving and reloading the file.
    You can also delete them manually by clicking *Purge* in the header.

### Search

The textbox lets you filter the tree by typing a substring. You can focus it using `Ctrl`-`F`
or clear it using `Alt`-`F`.

### Filter

The funnel icon in the header offers further control over what is displayed in the editor.
Depending on the *Display Mode*, some options are not available.

Restriction Toggles
:   Set which [Restriction Toggles](#restriction-toggles) should be visible.

Sort Alphabetically
:   Sort the entries alphabetically.

Sync Selection
:   Whether to synchronize the Outliner selection to and from the
    [3D Viewport](../3dview/index.xhtml) and
    [Video Sequencer](../../video_editing/index.xhtml) editors.

Show Mode Column
:   Show the column for toggling the [object interaction mode](../3dview/modes.xhtml).

Search

Exact Match
:   Only show the items whose name fully matches the [search text](#bpy-types-spaceoutliner-filter-text)
    rather than only containing it as a substring.

Case Sensitive
:   Take lower/upper case into account when comparing the search text to the item names.

Filter

All View Layers
:   Show all the [view layers](../../render/layers/index.xhtml) in the scene instead of only the active one.
    Combined with disabling the *Objects* filter, this gives a compact overview of all the collections in relation
    to the view layers.

Collections
:   Show the collections in the scene hierarchy. Only the collections themselves are hidden when this option
    is disabled; the objects within them remain visible.

Objects
:   Show the objects in the scene hierarchy. Disabling this gives you an overview of just the collections.

Object State
:   List the objects based on their state or restrictions.
    The results can be inverted using the *Invert* toggle button.

    All:
    :   Show all objects.

    Visible:
    :   Only show the objects that are visible in the 3D Viewport.
        This takes both the *Hide in Viewports* and *Disable in Viewports* settings into account;
        see [Restriction Toggles](#editors-outliner-interface-restriction-columns).

    Selected:
    :   Only show the object(s) that are currently [selected](../../scene_layout/object/selecting.xhtml)
        in the 3D Viewport.

    Active:
    :   Only show the active object (typically the one that was selected last).

    Selectable:
    :   Only show the objects that can be selected in the 3D Viewport;
        see [Restriction Toggles](#editors-outliner-interface-restriction-columns).

Object Contents
:   List relevant materials, modifiers, mesh data and so on as children of each object.

Object Children
:   Show [child objects](../../scene_layout/object/editing/parent.xhtml) as child nodes in the Outliner tree.
    When disabled, child objects are shown as sibling nodes instead (unless they’re in a different collection
    than their parent, in which case they’re not shown in the parent’s collection at all).

Meshes/Lights/…
:   Lets you filter out objects by type.

System Overrides
:   Shows the data-block properties that are defined/controlled automatically (e.g. to make data-blocks
    point to overridden data instead of the original). Only available in the *Library Overrides*
    [Display Mode](#display-mode).

### Miscellaneous

Some options in the header will only show if compatible with the active [Display Mode](#display-mode).

New Collection View Layer
:   Add a new collection inside the selected one.

Filter by Type Blender File Unused Data
:   Restrict the type of the data-blocks shown in the Outliner.

Keying Sets (Data API) Data API
:   Add/Remove the selected property to/from the active [Keying Set](../../animation/keyframes/keying_sets.xhtml).

Drivers
:   Add/Remove [Drivers](../../animation/drivers/index.xhtml) to the selected item.

Purge (Orphan Data) Unused Data
:   Opens a dialog to remove unused data-blocks from both the current blend-file or any
    [Linked Data](../../files/linked_libraries/link_append.xhtml) (cannot be undone).

    Local Data-Blocks
    :   Removes unused data-blocks from the current blend-file.

    Linked Data-Blocks
    :   Removes unused data-blocks from [Linked Data](../../files/linked_libraries/link_append.xhtml).

    Recursive Delete
    :   Removes data-blocks only used by unused data-blocks,
        ensuring that no orphaned data-blocks remain after execution.