macOS uses additional displays as an extended desktop or a video mirror (not to be confused with text flipping). Extended desktop uses the display as additional screen space (usually the default). Video mirroring makes the display clone the content of an existing display.
Use extended desktop for text flipping and general dual-screen use. You may want to use video mirroring for performance reasons if you do not need to use text flipping.
To change extended desktop or video mirroring:
- Connect a second display.
- Open System Settings and select “Displays”.
- Click the display to select it, then set the “Use as” pop-up button to make it an “Extended display” or make it a video mirror (clone) of another display.
Older Macs
Older Macs with System Preferences have an “Arrangement” tab with the same functions. Under the “Arrangement” tab, hold the Option key, then drag and drop one display rectangle onto another display rectangle to mirror only those displays. Similarly, unmirror or mirror all displays with the Mirroring checkbox.
Tip
On modern Macs, ⌘F1 (or ⌘ Brightness Down) toggles video mirroring.
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