Method for a safety-relevant input on a graphical user interface, wherein a computer generates image data for a display and comprises an input device for controlling the user interface, wherein the method includes: transmitting computer-generated image data from the computer to the display via an image data line; displaying a user interface on the display with at least one graphical control element that is selectable in a user-controlled manner using the input device; and wherein a monitoring unit (11; 21) is connected to the image data line and, for a safety function, reads out at least portions of the image data; characterized in that - the monitoring unit (11; 21) is supplied with input information coming from the input device and depending on which user-controlled selection of the control element is recognizable by the monitoring unit; - the monitoring unit (11; 21) is connected to a confirmation device (14; 23) for receiving a user-controlled confirmation via a safe signal path (11B; 11C), and - the monitoring unit (11; 21) ensures and/or verifies that a recognized selection of the control element is correctly represented in the image data supplied to the display; and - the monitoring unit (11; 21), upon receipt of a user-controlled confirmation during a displayed selection of the control element, releases or triggers a safety-relevant control command associated with the control element, in particular outputs the control command via a safe signal path. transmitting computer-generated image data from the computer to the display via an image data line; displaying a user interface on the display with at least one graphical control element that is selectable in a user-controlled manner using the input device; and wherein a monitoring unit (11; 21) is connected to the image data line and, for a safety function, reads out at least portions of the image data; characterized in that - the monitoring unit (11; 21) is supplied with input information coming from the input device and depending on which user-controlled selection of the control element is recognizable by the monitoring unit; - the monitoring unit (11; 21) is connected to a confirmation device (14; 23) for receiving a user-controlled confirmation via a safe signal path (11B; 11C), and - the monitoring unit (11; 21) ensures and/or verifies that a recognized selection of the control element is correctly represented in the image data supplied to the display; and - the monitoring unit (11; 21), upon receipt of a user-controlled confirmation during a displayed selection of the control element, releases or triggers a safety-relevant control command associated with the control element, in particular outputs the control command via a safe signal path. - the monitoring unit (11; 21) is supplied with input information coming from the input device and depending on which user-controlled selection of the control element is recognizable by the monitoring unit; - the monitoring unit (11; 21) is connected to a confirmation device (14; 23) for receiving a user-controlled confirmation via a safe signal path (11B; 11C), and - the monitoring unit (11; 21) ensures and/or verifies that a recognized selection of the control element is correctly represented in the image data supplied to the display; and - the monitoring unit (11; 21), upon receipt of a user-controlled confirmation during a displayed selection of the control element, releases or triggers a safety-relevant control command associated with the control element, in particular outputs the control command via a safe signal path.