Learn about overscan and underscan

You might see the terms "overscan" or "underscan" used in OS X, Apple TV, or your favorite app. This article explains what these terms mean, and how selecting or changing related settings affect output to a television. 

Overscan and underscan

Some televisions draw the borders of an image beyond the normally visible area. Some TVs also have bezels that cover a small percentage of their physical screen. Either of these can conditions result in a slight cropping of the visible image on the TV screen. This is known as "overscan". 

If you see black bars around the image you're viewing, the dimensions of the image might not be the same proportions as your TV or projector. This is known as "underscan". This can be normal depending on the image you're viewing, the settings on your device, and the way you've configured your TV or projector.

Adjust the image

You can adjust the image sent from your Mac to help it fit on your TV or projector. Apple TV also includes a setting for content viewed from a Mac or iOS device using AirPlay. You should also check your TV or projector for similar settings on the device's built-in controls or remote.

On your Mac

If you don't see the OS X menu bar or Dock when mirroring your Mac to a TV, try adjusting the overscan or underscan setting in the Displays pane of System Preferences.

Some devices also support more than one screen resolution. If you see an option to change the screen resolution in the Displays window, try selecting a resolution that matches the dimensions of the TV or projector you're using. Check the documentation that came with your TV or projector to find out which resolutions it supports.

On your Apple TV

If you're viewing content from a Mac or iOS device using AirPlay with your Apple TV, you can adjust the Overscan setting on your Apple TV to help match the size of your screen.

On your Apple TV, go to Settings > Audio & Video > Adjust for AirPlay Overscan. Turn this setting on or off, then AirPlay to your device to see if the image looks better.

On your HDTV or projector

Some HDTVs and projectors have built-in settings you can also use to adjust overscan or underscan. Look for a Zoom button on your remote, or check your TV or projector's built-in menus and controls.

You should also check your TV or projector for presentation mode, computer mode, or a similar setting. Some devices change the sharpness or brightness of the display depending on this setting. Selecting the proper mode on your TV or projector can improve text and images when viewing content from your Mac or Apple TV using AirPlay.

For more help, consult the documentation that came with your device, or the manufacturer's website.

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