OS X Mountain Lion: Connect multiple displays to your Mac
You may be able to connect more than one display to your Mac. To do so, you need a video cable for each display. See the manual that came with your computer or graphics card to find out what you need.
After you connect the displays to your computer, you can choose whether to use the displays as an extended desktop or for video mirroring. If you choose video mirroring, the displays each show the same image. If you choose an extended desktop, the displays form one large continuous desktop.
If you are playing a DVD on a television connected to your computer, click the Arrangement button in Displays preferences and move the menu bar to the television. If you don’t see an Arrangement button, your computer is only capable of mirroring (showing the same image on all screens). For more information, see the manual that came with your computer.
Find the manual for your Mac
Connect the displays to your computer
For each display you want to use, connect a video cable (and adapter, if necessary) from a video output port on your computer or graphics card to the video input port on the display. Make sure the cables are securely connected or you may not be able to see an image on the display.
If your Mac has one or more Thunderbolt ports, you can connect up to two displays to those ports. If the displays also have Thunderbolt ports, you can connect one display to another, and then connect one of the displays to a Thunderbolt port on your Mac. Or you can connect each display to different Thunderbolt ports on your Mac.
If a display is not recognized, click the Detect Displays button in Displays preferences, or try putting your computer to sleep and then waking it.
Set up the displays as an extended desktop
- Choose Apple menu > System Preferences, click Displays, and then click Arrangement.
- Follow the onscreen instructions.
Set up the displays for video mirroring
- Choose Apple menu > System Preferences, and then click Displays.
- Set both displays to the same resolution.
- Click Arrangement, and then select Mirror Displays.
Set up some displays for mirroring and others for an extended desktop
If your computer is connected to more than two displays, you can specify that some are mirrored displays and others show the extended desktop. For example, if you have three displays, you can have two displays showing the same information and the third display showing the extended desktop.
- Set up all the displays as an extended desktop.
- Option-drag a display icon onto another display icon to mirror those two displays.