Rudolf from Switzerland asked me if he could use his 10 year old iMac as a monitor for one Mac mini 2018 he intends to buy. Since this question is also interesting for other Apple users, I have prepared the relevant information as a contribution. Because not only the Mac mini, but also the MacBook Pro / Air can theoretically be coupled with the iMac via screen synchronization for extended display. How to do this and what requirements must be met, you will read in the following.
Chapter in this post:
- 1 Using the iMac as a monitor - requirements
- 2 Old Apple iMac as a screen extension - cable
- 3 Update 12.12.2020/XNUMX/XNUMX: Mini-DP to USB-C solution
- 4 Warning: some USB-C to DisplayPort cables do not work
- 5 Activate screen synchronization mode - Here's how
- 6 Troubleshooting - If it doesn't work right away
- 7 Update 18.03.2021/XNUMX/XNUMX: Use the iMac as a PC display?
- 8 Answer to Rudolf's question - Yes, it should work!
- 9 Apple iMac as a Monitor - Questions and Answers on the Subject
- 10 Similar posts
Using the iMac as a monitor - requirements
There are certain prerequisites and system requirements that must be met so that the iMac can be used as an (external) monitor on a Mac, Mac mini or MacBook. In the following list I have put together the compatible models for you. Because not every Apple iMac is made for screen synchronization mode:
- iMac end of 2009 27 "
- iMac mid 2010 27 "
- iMac mid-2011 to mid-2014
iMacs from the end of 2014 with 27 “and 5K retina displays cannot be used. In addition, it must be ensured that the above models have Mac OS X 10.6.1 or a newer version of macOS, but may have a maximum of macOS High Sierra. The more recent macOS versions (Mojave, Catalina, Big Sur) no longer support the target display mode. You also need a keyboard that plugs into the iMac - the original model is best.
If your devices and operating systems do not belong to those mentioned above or if setting up the Display Target Mode is too complicated for you, continue here: Use old iMac as a monitor via USB (without official compatibility). This is how you can get a high-resolution second display more easily and without having to buy a new monitor!
Old Apple iMac as a screen extension - cable
So now you already know which Apple computers are required with which operating system and which peripherals. But of course the image source, i.e. the new computer, and the model that is stored as a display have to be connected. The connection can be established using Mini DisplayPort cables and Thunderbolt cables as well as a combination of the two. Here is an overview:
|iMac that is used as a monitor||Cable for the monitor function||Connection to the other Apple computer|
|iMac (27 ″, late 2009)||Mini DisplayPort to Mini DisplayPort
|Mini DisplayPort or Thunderbolt
(on Amazon: MiniDP / TB3)
|iMac (27 ″, mid 2010)||Mini DisplayPort to Mini DisplayPort
|Mini DisplayPort or Thunderbolt
(on Amazon: MiniDP / TB3)
|iMac (mid 2011 to mid 2014)||Thunderbolt
Source: Apple Support Document HT204592
Update 12.12.2020/XNUMX/XNUMX: Mini-DP to USB-C solution
If your Macs have the sockets shown above, then I have a combination of cable and adapter for you that works with a high degree of security. A reader (thank you, Robert!) Wrote to me that he is using an old iMac late 2009 on the Mac Mini 2018:
From the two products you put together an adapter cable that should also do its job for you. You may not have to read any further in the article, because there are other solutions below that did not work for all readers. But I still want to leave it in here as a backup.
Warning: some USB-C to DisplayPort cables do not work
As a reader recently wrote to me, the connection between iMac and MacBook Pro is not working. He used a cable that fits into the iMac (DisplayPort) and the MacBook Pro (USB-C), but it still doesn't work.
At first I thought it was because the cable is not a Thunderbolt 3 cable, but it seems that there are also USB-C to DisplayPort cables that do their job. So there is still a little trial and error. I've listed both variants here. Once the solution with the Apple Thunderbolt cable and adapter and once a USB-C to mini Displayport cable, which according to a reader (see comments below) works for him where the Apple solution has failed:
1st option: Thunderbolt adapter and Thunderbolt 2 cable
2nd option: USB-C to mini DisplayPort cable
I would recommend ordering both and then keeping the solution that works. The other cables or adapters can then be sent back to Amazon.
Activate screen synchronization mode - Here's how
If you have both Apple computers connected with the correct cable, both are connected to a power source and switched on, and the old iMac has a keyboard, then you can start. Just follow these steps and nothing should stand in the way of using the old computer as a monitor:
- Connect both computers together and turn them on
- Leave iMac on the login screen
- Log into a macOS account on the other computer
- Press cmd + F2 on the iMac
- If that doesn't work: press cmd + Fn + F2
Also interesting: “Keyboard shortcuts for the Mac” book tip
Troubleshooting - If it doesn't work right away
Points 4 and 5 are listed as alternatives, as the menu item “Use the F1, F2 etc. keys as standard function keys” could be activated in the system settings of the secondary device. So if the combination of Command and F2 doesn't work, just try the alternative. In addition, this shortcut has to be pressed on the keyboard that is connected to the secondary computer - pressing it on the Mac mini, MacBook or other connected computer does nothing. In addition, the problem could be with an Apple or third-party keyboard that is too old. It is best to use the keyboard that came with the iMac.
It is also essential that the secondary computer is in the macOS login window. No user account must be open or any version of Windows running through Boot Camp. In addition, the primary Mac must be logged into a user account. If that still doesn't work, it can help to connect a “real” external monitor first and then try the iMac again. Using older iMacs as monitors is generally a better idea, because the color fidelity and sharpness of the displays (even if they are not yet 5K Retina displays) have already been impressive.
Update 18.03.2021/XNUMX/XNUMX: Use iMac as a PC display?
Yes, that should work too. In the comments below, I sometimes made different claims because I didn't know any better at the time, but it is correct: You can also use an iMac as a monitor for a Windows laptop or desktop computer. The prerequisites and the procedure are as described above.
Answer to Rudolf's question - Yes, it should work!
If the old iMac is one of the above models and connect it to a Thunderbolt 3 (USB-C) to Mini DisplayPort cable is used, the new Mac mini 2018 should be able to successfully transmit video and audio signals. By the way: The linked cable should be perfect for this; a customer review (in English, but at least detailed) says the following:
I am really excited about this because it was very difficult to find the right cable. I have just received the cable USB C to Mini DisplayPort to connect my Mac Book Pro 2017 with touch bar with my iMac (middle 2010) to use it as a monitor. It works perfect !!! It saved me from buying a new Monitor or a new iMac.
Apple iMac as a monitor - questions and answers on the subject
Don't you want to buy an extra screen for your new Mac, Mac mini, MacBook or another iMac because you still have an old complete computer? Cupertino standing there, I hope this post was able to help you. Thunderbolt 3, Thunderbolt 2 and Mini DisplayPort allow you to connect quickly and use the screen synchronization mode. If you have any questions, tips or tricks on this or related topics, please leave a comment!
Jens has been running the blog since 2012. He acts as Sir Apfelot for his readers and helps them with technical problems. In his spare time he rides electric unicycles, takes photos (preferably with the iPhone, of course), climbs around in the Hessian mountains or hikes with the family. His articles deal with Apple products, news from the world of drones or solutions to current bugs.