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Using iMac Late 2015 as a second display screen for MacBook Air 2017

How can I use my iMac 21.5inch late 2015 with Monterey 12.4 OS as a display for my MacBook Air 13 inch 2017 with Big Sur 11.2.3 OS? I've tried a thunderbolt cable and the Fn-Command-F option, neither of those work. Screen sharing doesn't work either.

My iMac has become so slow that I thought I'd use my MacBook instead, but I like the big screen of my iMac. Anybody got any ideas?

iPad Pro, iPadOS 16

Posted on Sep 21, 2023 2:15 AM

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Sep 23, 2023 3:13 AM in response to LML2023

LML2023 wrote:

Update:
Apparently it won't work using the current operating system. I need to go back to High Sierra or earlier. To do this I first need to wipe my Mac clean, and this involves saving all my data, files and photos, etc. onto external memory. Now waiting for external drive to be delivered.


The Late 2015 iMacs do not support Target Display Mode. I don't know whether your 21.5" Late 2015 iMac is a Retina model or a non-Retina model (Apple made both) – but the last iMacs that could operate in Target Display Mode were the Mid 2014 ones.


So don't bother wiping your iMac clean and downgrading the OS, just to try using TDM. You'll just find out that you've gone to all that trouble to try to use a feature that that iMac never had.


Using iMac Late 2015 as a second display screen for MacBook Air 2017

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