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I have a Surface Pro 4 and an iMac (late 2019). I would like to connect my Surface Pro to the iMac to use the iMac screen as a second monitor. Is that possible?

What are the requirements to use an iMac as a second screen?

Tetsujin
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jtag47
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2 Answers2

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No. You cannot do this. The 2019 iMac is not supported for Target Display Mode.

This is an attempt to write a canonical QA for this issue, as per the Meta post: Where is the list of canonical questions stored for Ask Different? I expect it to be periodically edited with the goal of becoming a comprehensive information resource.

Which iMac Models Support Target Display Mode?

  • General Rule of Thumb: If it's after 2014, Target Display Mode isn't supported.

  • 24 and 27 inch iMacs from 2009 - 2010 support TDM via Thunderbolt or mini DisplayPort (mDP)

  • All iMacs (21 inch and 27 inch) from 2011 through mid 2014 support TDM via Thunderbolt only.

  • Retina iMacs from late 2014 and on do not support TDM at all.


Which Mac models can you use as a source?

All Mac models through 2019 that meet the above requirements can use Target Display Mode. Currently, 2020 Macs will not connect (i.e. 2020 MacBook Pro running Catalina), but a 2019 MacBook Pro also running Catalina works fine.

What version of macOS is required?

  • On the Target iMac, it must be running High Sierra or earlier.
  • TDM is not supported on any iMac running Mojave or later.
  • It doesn't matter what version of macOS you're using on your source computer

Can I use my iMac as a Target Display for a PC?

Yes! As long as the target Mac meets the above requirements and the PC has the proper port; Thunderbolt or mDP. The OS on the source computer doesn't matter at all.

Can I use a "bricked" or broken iMac as a Target Display?

No. Your iMac must be a fully functional iMac running High Sierra or later.

Sources & Further Reading:

Allan
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  • I am using a 2013 iMac in TDM while the same Mac is booted to Catalina. So your statement "On the Target iMac, it must be running High Sierra or earlier" is not true. – David Anderson Apr 28 '20 at 03:34
  • First link under Sources and Further Reading, *Apple* states the target must be HS or earlier, “It does not work with Mojave or later”. Apple’s words, not mine. – Allan May 10 '20 at 02:30
  • I do not understand your previous comment. I posted your statement "On the Target iMac, it must be running High Sierra or earlier" is not true. This statement is not the same as “It does not work with macOS Mojave or later”. – David Anderson May 10 '20 at 02:40
  • Did you visit the link? “ Target display mode requires macOS High Sierra or earlier on the iMac used as the external display. It does not work with macOS Mojave or later.” – Allan May 10 '20 at 02:42
  • This is correct, but the Target display can be booted to and running Catalina. Nothing in the statement "Target display mode requires macOS High Sierra or earlier on the iMac used as the external display. It does not work with macOS Mojave or later.” says otherwise. – David Anderson May 10 '20 at 02:45
  • The “target display” and “the iMac used as the external display” are one in the same. So, I don’t know what difference you're trying to highlight here. For the record, I personally tested a 2012 iMac with Mojave in TDM and it did not work, just as Apple described. – Allan May 10 '20 at 02:50
  • OK, maybe you can help figure this out. In my case the 2013 iMac is in TDM while running Catalina. This iMac also has High Sierra installed on a different APFS volume. A 2011 iMac running High Sierra is using the 2013 iMac as an external display. The two Mac are connected using thunderbolt cable and therefore the Network pane of System Preferences on both Macs show a Thunderbolt Bridge between the machines. So I do not know if the software to run in TDM is coming from the HS installed on the 2011 or 2013 iMac. When you tested, did either Mac have HS? – David Anderson May 10 '20 at 03:05
  • The source was a MacBook Pro 13 (can’t remember the year), but running Catalina snd used a TB 1/2 cable. The iMac had El Capitan and TDM worked. It was upgraded to Mojave and then it didn’t. High Sierra was on none of the machines. The only thing I can think of was the iMac had a clean install and not an in place upgrade. – Allan May 10 '20 at 03:10
  • Here is a screen shot of the display on the 2013 iMac. This 2013 iMac in running Cataline and is in TDM. The 2013 iMac is being used as a external display connected to a 2011 iMac. The large screen sharing window in the background shows the desktop of the 2013 iMac. You can see the 2013 iMac is running Catalina while in TDM. – David Anderson May 10 '20 at 03:33
  • I’m not saying I doubt you. I’m only posting what Apple states and what I verified. – Allan May 10 '20 at 03:36
  • An update to my original comments: My 2013 iMac display works in TDM when running Catalina. However, the sound does not. For the sound to work, the 2013 iMac needs to be running High Sierra or earlier. – David Anderson Mar 17 '21 at 16:12
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    I think Luna Display should be mentioned somewhere. Academically, it doesn't answer the question directly, but practically, it does solve the problem, in that it lets you use a recent Mac as a target display. – Beetle Sep 05 '22 at 12:26
  • It is interesting to see that Luna Display supports connection by a USB A-to-C cable. I've seen plenty on StackExchange that will claim communication but such a cable is impossible, but this is clearly not true given this example. It just takes the right kind of software, and motivation to write it and support it. – MacGuffin Aug 21 '23 at 00:30
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Hardware based, No.

However - you could bootcamp the iMac and use Windows 10's built in display extension features to create a software base solution?

isyme59
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  • This is a nice idea, but looks like it won't work: https://apple.stackexchange.com/questions/260451/is-bootcamp-6-0-supporting-target-display-mode-of-an-imac-to-a-windows-10-os#:~:text=Target%20display%20mode%20only%20works,t%20supported%20in%20Boot%20Camp. – optimus_prime Apr 04 '23 at 15:47
  • @optimus_prime The link given doesn't show Windows display extention won't work, only that Target Dispaly Mode requires macOS installed. Windows display extension is something similar but not related to TDM. – MacGuffin Aug 21 '23 at 00:32