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I have a 2012 iMac running Catalina and I'd like to use it as a secondary display to my MacBook Pro. I connected the two computers via a USB cable and hit both ⌘ CommandF2 and then tried ⌘ CommandFnF2. It's not working.

Do I need to use a Thunderbolt? Any input/advice would be most appreciated.

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  • This question is not a duplicate and the answer referenced above pertains to connecting a Microsoft Surface 4 to a 2019 iMac and not a MacBook Pro connected to a 2012 iMac as pertains to the questions above.
    – Gerard de Jong
    Commented Aug 11, 2020 at 17:12
  • Concur, this is NOT a duplicate.
    – James Brickley
    Commented Aug 22, 2020 at 19:38
  • @GerarddeJong If you read the answer, you’ll find that it’s canonical, meaning it applies to all situations and not limited to what’s in the question. This question is comprehensive and answered by that one.
    – Allan
    Commented Aug 26, 2020 at 8:23
  • Thank you @Allan but I respectfully disagree on account of the question pertaining to an entirely different platform (Microsoft vs. Mac), this question is about connecting different hardware i.e. a MacBook vs. a Surface Pro 4. I'm not the only person who things this should not be marked as a duplicate (as per the comment's above). Can we please have an un based third party make a call on this one.
    – Gerard de Jong
    Commented Aug 26, 2020 at 13:24
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    @GerarddeJong We close questions as duplicates if answers to an existing question answer a new question as well. In the actual case the answer on the linked question explains under which conditions an iMac can be used as secondary display for a MacBook Pro and what kind of cable is required. So at least from the information we currently have this looks like a duplicate to the "Do I need to use Thunderbolt" question in the post above.
    – nohillside ♦
    Commented Aug 26, 2020 at 14:40

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enter image description here Don’t use a cable like the one shown above! These do not contain the required licensed Thunderbolt chips (inside the connectors) to support Thunderbolt protocol. While they will work for a connection to a DisplayPort only monitor input, they will not support a Thunderbolt Display or iMac in Target Display Mode.

You need a cable that looks like the one below that shows a Thunderbolt Logo on each connector indicating it’s compatibility. I recommend the 2m cable, the 0.5 is too short unless you are comfortable leaving your MacBook closed under your iMac.

enter image description here If your MacBook Pro only has USB type C ports you’ll need to check which of those ports support Thunderbolt 3 and use Thunderbolt 3 to Thunderbolt 2 converter from Apple with a Thunderbolt 2 male-to-male cable to connect it to your iMac.

Here's an picture of the Thunderbolt 2 converter from Apple that'll do the trick.

enter image description here

Also check your MacBook's specs, and be sure to use the Thunderbolt ports, some are only USB C and it can be hard to tell.

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  • I did some research and I what I read was that all ports on the Macbook Pro are Thunderbolt 3. I purchased a "USB C to Mini DisplayPort Cable, QCEs Type C to Mini DP Adapter 4K 6.6Ft Cord Thunderbolt 3 Compatible with MacBook Pro 2018 iPad Pro iMac 2019". I've tried every port on both the MacBook and the two on the iMac. Any idea what I'm doing wrong?
    – Shannon Poulos
    Commented Aug 21, 2020 at 21:57
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    Thunderbolt and USB-C are different communication standards but they use the same port/connector on your MacBook. The USB C to Mini DisplayPort Cable that you've purchased with convert USB C to Display Port which unfortunately is not going to work as your iMac requires Thunderbolt (not Displayport) for Target Display mode to work. What you actually need is Thunderbolt 3 to Thunderbolt 2. I'll add a picture to my original answer.
    – Gerard de Jong
    Commented Aug 22, 2020 at 17:29
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    @GerarddJong is correct, you need the Apple USB-C Thunderbolt 2/3 adapter and a Thunderbolt 2 cable from the 2012 iMac to the adapter to the MacBook Pro.
    – James Brickley
    Commented Aug 22, 2020 at 19:37
  • I bought a cable that I thought was Thunderbolt 3 to Thunderbolt 2. But it's not working. I'll add a photo.
    – Shannon Poulos
    Commented Aug 24, 2020 at 17:49
  • @ShannonPoulos please post the photo and let’s see. I assume you’re using original Apple branded adapters and an original Apple Thunderbolt cable. Let’s see.
    – Gerard de Jong
    Commented Aug 24, 2020 at 17:58

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