Missing Target Display
by ZHONGWEI QIN
Q MyiMac 27-inch running High Sierra won’t connect to my M1 MacBook Air using Target Display mode. What am I missing?
A TargetDisplay Mode is only available with specific combinations of Macs running certain versions of macOS. The Target, to be used as a second display, must be an iMac introduced between 2011 and mid-2014, or a 24- or 27-inch iMac introduced in 2009/10. That must be running no version of macOS later than 10.13 High Sierra.