Overscan refers to a cropped image on your TV screen. Here are some examples:
- A setting on your TV zooms in on film content, so that you can't see the outermost edges of the film.
- Your TV's plastic border blocks some of the TV screen, so that you can't see the edges of the content.
Underscan is usually intended, and refers to black bars that appear around a film or TV show. The bars appear because the content was filmed in a different proportion to that of your TV screen. Here are some examples:
- Black bars appear above and below a film because it has a wider aspect ratio than your TV screen.
- Black bars appear on the left and right of a TV show, because it has a smaller aspect ratio than your TV screen.
Adjust the screen size
When viewing content from your Mac or iOS device on your TV or projector, you can adjust the screen size to fit your TV or projector. You can look for these settings on your Mac or Apple TV, or in the menu of your TV or projector.
Adjust from the menu on your Mac
While mirroring your Mac to a TV or projector, go to System Preferences > Displays. From here, you can use the slider to adjust the overscan or underscan setting.
If you see an option to change the screen resolution, you can choose the one that matches the dimensions of your TV or projector. If necessary, check your TV or projector's manual to find the display resolution.
Adjust from the menu on your Apple TV
While using AirPlay to watch content from your Mac or iOS device on your TV or projector, you can adjust the size of the picture in the Settings menu of your Apple TV.
- On Apple TV 4K or Apple TV HD, go to Settings > AirPlay > AirPlay Display Underscan.
- On Apple TV (2nd or 3rd Generation), go to Settings > Audio & Video > Adjust for AirPlay Overscan.
Adjust from the menu on your TV or projector
Some TVs and projectors let you adjust overscan or underscan from a settings menu or button on your remote. Look for a Zoom button or check your TV or projector for a menu called Aspect Ratio, presentation mode, computer mode or a similar setting.
For more help, check the manual that came with your TV or projector or contact the manufacturer.