Video mirroring duplicates your entire desktop across all connected displays.

Note: These options are available when an external display is connected.

1. On your Mac, choose Apple menu  > System Settings, then click Displays in the sidebar
2. Click the name of your display, and then select Mirror for Built-in Display

To instantly mirror your Mac display to an external monitor, press Command + F1. Press the same keys again to return to the original display setup.