I want to use my iMac as a monitor for my MacBook Air. I have a thunderbolt cable I got from Apple today. My iMac has macOS Sierra version 10.12.6 and my MacBook Air has macOS Big Sur 11.4. When I press command F2 the iMac just has a grey screen. I have tried the trouble shooting tips by Apple to no avail.
Unfortunately, that setup is not supported by Apple. The iMac cannot be used as a monitor for any of the newest Macs and target display mode is no longer a feature of macOS. It is wholly unsupported in macOS Big Sur.
As Apple states them, here are the rules for target display mode on iMac:
click> https://support.apple.com/en-us/HT204592
Per the link above:
• Make sure that your target iMac is using macOS High Sierra 10.13.6 or earlier.
• The source Mac must have been introduced in 2019 or earlier and have macOS Catalina or earlier installed.
Thanks. That is too bad. I guess I will return the thunder cable.
How to get the iMac to work as a monitor
