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Using an iMac As an External Display: How to Use Target Display Mode

A Guide to Using Target Display Mode


Desktop computer in a home environment
David Epperson/Photographer's Choice RF/Getty Images

The 27-inch iMacs introduced in late 2009 have many exciting features, but one that’s been a little overlooked is the ability to use the 27-inch iMac’s display as a separate monitor for video devices.

Apple envisioned the iMac being used with DVD and Blu-ray players, as an HDTV display, and even as a display for another computer.

Connecting a Video Source to Your iMac

The 27-inch iMac has a bi-directional Mini DisplayPort that can be used to drive a second monitor. The same Mini DisplayPort can be used as a video input that allows your iMac to serve as a monitor for an external video source. All you need is the proper adapter.

The Mini DisplayPort in the 27-inch iMac can only receive DisplayPort-compatible video and audio. It can’t receive analog video or audio sources, such as those from a VGA connector, but it’s possible to use adapters for digital DVI, HDMI, etc.

At the time of the 27-inch iMac’s introduction, no adapters for use with the bi-directional Mini DisplayPort were available, but Apple promised that third-party adapters would be available soon. Once adapters are available, you can easily connect your DVD or Blu-ray video source, HDTV tuner, another computer, or other compatible video/audio source to your iMac for display.

Connect the male Mini DisplayPort connector to your 27-inch iMac. Your iMac can be on when you do this; there’s no need to shut it down first.

Enable Target Display Mode

  1. Your iMac should automatically recognize the presence of a digital video signal at the Mini DisplayPort and enter Target Display Mode.
  2. If your iMac does not automatically enter Target Display Mode, press command + F2 to manually enter Target Display Mode.

Exit Target Display Mode

You can manually turn off Target Display Mode by pressing the command + F2 keyboard combination, or by disconnecting or turning off the video device connected to your iMac.

Things to Consider

Your iMac will continue to run OS X as well as any applications that were open when it entered Target Display Mode.

While in Target Display Mode, only the keyboard’s display brightness, volume, and Target Display Mode key combinations are active. Any other keyboard input will be ignored. USB, FireWire, and inputs other than the keyboard will also be ignored.

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