Target Display Mode lets an older iMac show the screen of another Mac. Apple supports it only on these models:

  • iMacs introduced in 2011, 2012, 2013 and mid 2014, with macOS High Sierra 10.13.6 or earlier, connected with a Thunderbolt or Thunderbolt 2 cable;
  • 24‑inch and 27‑inch iMacs introduced in 2009 and 2010, with macOS High Sierra 10.13.6 or earlier, connected with a Mini DisplayPort cable.

The other Mac must be from 2019 or earlier, with macOS Catalina 10.15.8 or earlier. So no iMac from late 2014 on, and no Mac with Apple silicon, can use Target Display Mode. Apple: Use iMac as a display with target display mode

Second Display on newer iMacs

Second Display works on any iMac with macOS 12.3 or later: the models from late 2015 on, up to iMac with Apple silicon. The Mac you work on needs macOS 14 or later. Your Mac gets an extra display, as if you had plugged in a monitor, and sends its picture to the iMac:

  • over a Thunderbolt cable, lossless at Highest quality when the two Macs keep up with it;
  • over Wi‑Fi, Ethernet or a USB‑C cable without Thunderbolt, compressed to suit the connection.

In our tests a MacBook Pro with M3 Pro sent Highest to an iMac 24‑inch with M1 at 60 frames per second, over a Thunderbolt 4 cable. We haven’t measured older and Intel iMacs yet, nor tried the Thunderbolt 2 ports of the late 2015 models. The speed test recommends the quality your two Macs can keep up. Which iMacs can be a display

What’s different

  • Target Display Mode starts with Command‑F2 on the iMac’s keyboard. Second Display is an app on both Macs, and the two find each other on their own. Set up Second Display on both Macs
  • Target Display Mode can play sound through the iMac’s speakers. In this version Second Display doesn’t use the iMac’s keyboard, mouse or speakers. Keyboard, mouse and sound
  • To get back to the iMac’s own desktop, turn the display off in the menu of the Mac you work on, or quit Second Display on the iMac. Get back to the iMac’s own desktop
  • While it waits, the iMac’s screen sleeps like a monitor’s and wakes when your Mac connects. Sleep, wake and the lock screen