macOS: How to Turn Your iMac into a Secondary Display

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| How-To

If you have both a MacBook and an iMac, you can use the iMac as a display for the MacBook, or use an iMac as a display for another iMac. This gives you a bigger screen without needing to buy another screen.

[Connect a MacBook to an iMac’s Display with Target Display Mode …]

Target Display Mode

It’s called Target Display Mode, and it’s easy to start using. Apple has a support page about this, with system requirements and display options. I’ll provide the short version here.

imac and macbook using target display mode



System Requirements

  • A Mac notebook or desktop with a Mini DisplayPort or Thunderbolt port. If your Mac has Thunderbolt 3 (USB-C) ports, you can connect it using the Apple Thunderbolt 3 (USB-C) to Thunderbolt 2 Adapter.
  • Thunderbolt cable or a Mini DisplayPort to Mini DisplayPort cable
  • A supported iMac with OS X v10.6.1 or later

Entering Target Display Mode

  1. Turn on your iMac, and make sure the other Mac is logged in.
  2. Connect the Mini DisplayPort or Thunderbolt cable between the two computers.
  3. Press Command + F2 on the keyboard of the iMac that you want to use as a display.

Your target iMac will now display the desktop of the other, connected Mac. To exit TDM, just press Command + F2 again. It will also exit if you disconnect the cable or shut down/sleep the other Mac.

[Here’s a List of Dark Mode Apps in macOS Mojave]

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Looking at adding an extra “extended” monitor to my iMac 27″, would like it to be a monitor that looks like my iMac. I may add another to the other side, go 3-screens.

1) Does the other iMac have to be operational?

2) If I add two additional screens to my iMac, how do I connect them, even if they are not Mac products?


Another approach that’s workable is to link the two Macs via an Ethernet cable & use screen sharing. I was recently demonstrating a 2005 G4 PowerBook connected to a video projector. When I finished that, I needed to connect my Thunderbolt 3 MacBook Pro to the projector but didn’t have an adapter with me. But I did have an Ethernet adapter & Ethernet cable. I was able to share the MacBook Pro’s screen to the PowerBook & thence to the projector. At the same time, the Ethernet connection was providing internet to the PowerBook from Internet (wi-fi) Sharing via Ethernet… Read more »

Costas Constantinou

Also wondering if a USB C to Display port adapter cable would work?
– in the example of a new Macbook Pro and 2013 iMac (Which currently supports target display mode)

Colin Campbell
Colin Campbell

Thought this would be a good way to use my 2011 iMac screen with a Mac mini (assuming a new one ever appears) but from the Apple support article it seems to imply that the ‘master’ Mac must have a screen of its own so it can log into macOS first. Or is there another way of achieving this?


So according to Apple’s support page this only works on iMacs up to 2014. The 5K Retina and newer ones don’t support this. That really sucks. Anyone know why? Is it a hardware issue or software?


I use it on my 27″ 2010. It’s critical to me being able to work from home without rearranging my whole workstation. I simply plug in my work laptop to my iMac and bring my keyboard and mouse USB hub over.

I’ve been following a discussion about it on MR, where there was a glimmer of hope that it would return, but alas, nothing has come out of it: