If you have both a MacBook and an iMac, you can use the iMac as a secondary 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.

Using a Secondary Display

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.

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.

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Hi I did the following but my imac is dimmed. I can see the windows but the monitor is so dark. Before I can restart both and it works but now it doesn’t seem to work. Have you had this problem? Thanks

I have a 2015 Imac that from what I understand can no longer be upgraded. It is very slow and sluggish on startup making it hard for me to continue using it for my work. I’ve cleaned it up as much as possible and use an external drive for just about everything. I have a new mouse and keyboard that I upgraded not long ago, so I hate to buy a whole new Imac. I was thinking of getting the mini and using the Imac as my display for it. Would that work? If so, would it be a pain… Read more »

BTW my 2015 is a 21.5 inch with Catalina.

hi. i created an account just in order to leave this comment. sure, appreciate your effort, but please specify in your report that this TDM thing ONLY applies to 27” imacs, as i just recommended my sister based on this article and now she has to send back cables she bought in order to do this as our imac is 24”. i know it’s my fault not having verified straight away the source you’ve indicated. still i think it can be deceptive putting it the way you did, so telling this for possible future misadventurers following me

it’s basically NOT possible to use 24” imacs as external monitors. beware

(talking about imacs previous to 2011, of course)

Angel_eidell

How can i connect 2 imac? Both ports has usb c port

I’ve managed to connect my iMac and MacBook pro following your instructions. Thanks! Is it possible to make the MacBook pro the second monitor not the iMac? Doesn’t seem to do anything when I click fn, cmd and F2 on the MacBook pro. When I do it on the iMac it jumps into target display mode. I’m suing thunderbolt to thunderbolt.

BartHopkins

Hello – I’m betting you’ll know the answer to this. We just bought a 2020 Mac Mini, and we want to use our Late 2013 iMac as the monitor. What’s the easiest way to connect the Mac Mini and iMac … can I do it with a single cable and no adapter? Or do I have to buy an adapter AND a cable?
Thanks so much!
Bart

Ravenkeeper

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?

Empedro

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 »

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

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?

brett_x

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:

brett_x