Target Display Mode: Using an iMac as a 2nd monitor for a MacBook Pro or MacBook Air

I have a mid-2011 27″ iMac as a home computer, a 13″ MacBook Air as a travel computer, and recently got a 13″ MacBook Pro Retina as a work machine. I was thinking about getting a second monitor for using the MacBook Pro at home, but it turns out I can just use my 27″ iMac as a second monitor. The secret? Target Display Mode and a Thunderbolt cable.

Thunderbolt Cable
If you’re using a MacBook Pro as your main computer, but still have one of the iMac models below, Target Display Mode will help you breathe new life into your old machine. All you need is either a Mini DisplayPort or Thunderbolt cable. This makes an older iMac a great backup computer that doubles as a second monitor.

iMac (27-inch Late 2009) Mini DisplayPort to Mini DisplayPort Mini DisplayPort or Thunderbolt
iMac (27-inch Mid 2010) Mini DisplayPort to Mini DisplayPort Mini DisplayPort or Thunderbolt
iMac (21.5-inch, Mid 2011) Thunderbolt to Thunderbolt Thunderbolt
iMac (27-inch, Mid 2011) Thunderbolt to Thunderbolt Thunderbolt
iMac (21.5-inch, Late 2012) Thunderbolt to Thunderbolt Thunderbolt
iMac (27-inch, Late 2012) Thunderbolt to Thunderbolt Thunderbolt

To use your iMac as a second monitor:

  1. Turn on both machines
  2. Connect the cable
  3. Press Command-F2 on the keyboard of your iMac
    *If you’re using F1, F2, as standard function keys, then use Command-Fn-F2
    *
    Some older keyboards may not activate Target Display Mode. I’m using a newer standard Mac wired keyboard and it works great.

To exit Target Display Mode, just hit Command-F2 again or detach the cable. If one of the computers goes into sleep mode, that will also exit Target Display Mode.

3 thoughts on “Target Display Mode: Using an iMac as a 2nd monitor for a MacBook Pro or MacBook Air”

  1. Thanks Joe, I was wondering if that was possible. Do the USB ports on the iMac carry over to the laptop the way they would with a Cinema Display?

    1. You can’t access USB or Firewire devices connected to the iMac when using it as a second monitor. Any external drives or accessories need to be plugged into the primary machine.

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