Using Target Display Mode

Issue/Question

How can I use an iMac as a secondary monitor for another Mac computer?

Resolution

Target Display Mode on newer Macs with only USB-C ports is not supported by Apple. The use of USB-C to ThunderBolt to Display Port adapter will not work. This is not a standard setup and is unsupported. For older Macs, please see additional information below. 
The iMac must be one of a specific series in order to work as a secondary monitor, as well as having the necessary cable and port on the other Mac:
iMac Model Supporting Target Display Mode Cable Needed Port Needed on Other Mac
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 (Mid 2011-Mid 2014) Thunderbolt Thunderbolt
Please contact the ITS Service Desk if you need assistance determining if your iMac and other Mac computer are capable of connecting with Target Display Mode.
  1. Turn on the iMac.
  2. Turn on and log into the other Mac computer.
  3. Connect the appropriate cable between the two computers.
  4. On the keyboard of the iMac to be used as a display: Press Command-F2.
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