I have an old iMac (Retina 4K, 21.5-inch, 2019). I am thinking about to purchase a new Mac Mini and use the old iMac as external monitor. May I know if it is do-able? Thanks.
iMac 21.5″, macOS 15.3
The very restrictive hardware and OS requirements for what you wish to do—Target Disk Mode (TDM)— are laid out in this Apple support article:
Use your iMac as a display with target display mode - Apple Support
Note from the article that "this ship has sailed." No iMacs newer than mid-2014 can act as a monitor for another Mac, and the video-source Mac must older than 2020. Apple started the deprecation of TDM in late 2014 and threw the last shovel of dirt in its face in early 2020.
Today there is only one Mini display solution— a proper external monitor. Third-party workarounds are all too slow for a primary Mac Mini display.
The 2019 iMac cannot be used as a primary monitor for the Mac mini.
There is a third-party option, Luna Display (~$100), but its use is not suitable for enabling the iMac to be the primary display. Latency and pixelation are factors that make the solution problematic.
❝Like any product, Luna Display does have limitations and it’s not recommended for high-motion content. For example, I wouldn’t recommend using Luna Display for gaming or video editing.❞ - Luna website (Their emphasis, not mine.)
To use Luna you will need a primary display in order to setup the Mac mini and then to setup the Luna hardware and software.
Save yourself the headache and simply budget for a new monitor for your new mini. A display that compares favorably to that of the 2019 iMac can be had for ~$150-$350. And it'll just work.
Nope! If you purchase a new Mac mini, you will need an external display.
AFAIR this has been asked here before so try this Google search:
"Can I use old iMac 2019 as external monitor for Mac Mini site:discussions.apple.com"
Can I use old iMac 2019 as external monitor for Mac Mini
