Many readers want to use an old iMac as an external monitor — it ’s one of the most frequent Mac 911 question ! Wepreviously provided an almost - comprehensive answerto the doubtfulness before Applerestored a varlet on its sitethat offered full technical details after deleting it for a period of time .
How to use a new iMac as an extended display
If you are lucky enough to have one of the following iMacs that you could apply as an extended display you could practice Universal Control to do so .
desire to habituate your iMac as an surplus display here ’s what to do :
This is a little like the way Sidecar works when you share an iPad screenland with a Mac . The video display of your primary Mac is extended onto the show of your secondary Mac – you ca n’t access your secondary Mac .
How to use an old iMac as an extended display
If you are hope that it will be a way to practice an old iMac display with your new Mac then be prepared to be disappointed – the feature most likely wo n’t be compatible unless your iMac is one of those mentioned in the compatibility list above ( 2015 or 2017 and later depending on the sizing ) .
The general answer is often dissatisfactory : only iMacs exemplar shipped from 2009 to mid-2014 ( the seventh- and 8th - generation releases ) had the right graphic circuitry for what Apple called Target Display Mode .
But Apple imposed a second computer software requirement start with the freeing of macOS 10.15 Catalina . Despite the many people who have write in to ask if it ’s true , world wo n’t agitate . To use Target Display Mode , both the old iMac and the Mac you require to relate to it must be scarper outdated releases of macOS :
We do n’t know on the button what fall out . Did Apple remove codification in 10.14 Mohave that allowed an iMac to spark Target Display Mode ? Did the fellowship shed the instructions in macOS 11 Big Sur that still brook place video an iMac in the correct mode ? Apple does n’t reveal these sorts of point .
Some reader have find that with Big Sur instal on the controlling Mac they could , in fact , still drive an iMac ’s video display . However , we ’ve also heard from other readers who were frustrated they could not . One reader said that it only worked after pressing Command - F2 repeatedly on the iMac , sometimes a few seconds apart , which may have whelm the iMac ’s resistance — how , again , we do n’t have a go at it , since it ’s not hold up .
This Mac 911 article is in response to a question put in by Macworld reader Rick .
Ask Mac 911
We ’ve compiled a list of the questions we get expect most frequently along with solvent and link to columns : read our top-notch FAQ to see if your interrogative is cover . If not , we ’re always looking for young problems to solve ! netmail yours tomac911@macworld.comincluding CRT screen captures as appropriate , and whether you want your full name used . Not every question will be answered , we do n’t answer to e-mail , and we can not provide verbatim troubleshooting advice .
