So everyone, I think it’s because I’m running a version of Catalina on the target display.. how strange the os gives me the option to reboot in target display mode. Same set up didn’t work when I plugged in a 2018 MacBook Pro
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Connecting Mac mini to iMac as display
- Thread starter Chris Newbold
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iMac in target display must be on High Sierra or older. https://support.apple.com/en-us/HT204592
Yep, guess that answers it. Right cable.... wrong macOS version on the iMac. 
You might be confusing Target Display Mode with Target Disk Mode. They're two different things.
I would bet money that is your issue, as the Target Display Mode feature was remove on the target iMacs with Mojave.
The feature remained for the "source" Macs for Mojave and I am pretty sure also Catalina, but I have read that it was removed for Big Sur. This shouldn't matter for your though, as you are using a Mini Display Port iMac, and not a TB iMac as your target.
Maybe install High Sierra on a thumb drive, boot up, and just check to see if it works. Or you could partition your boot drive, giving yourself about 20GB a space, and install High Sierra.
The OP's situation is different than yours, as the OP is using a Late 2009 iMac as the target iMac. This was less restrictive than the TB iMacs, as you can plug in non-Mac video sources into them.
The TB3/TB2 bidirectional adapter normally would work for using a TB3 Mac as a source and a TB1 iMac as the target, but Apple recently removed the functionality via the OS of the source Mac.
Your situation is most likely because Apple has removed the Target Display Mode feature from the Big Sur OS for the source Macs. I am pretty sure I remember this discussion a while back with the Big Sur beta, people were speculating if Target Display Mode would return for the Launch of Big Sur.
Thanks for the info. You are unfortunately probably correct. It was nice while it lasted. RIP TDM.
I just received this from Apple Support. It sounds terminal for TDM:
“As you guessed, the keystrokes for Target Display Mode will no longer work. Instead, please review these helpful guides to understand your external display options:
https://s.apple.com/dE9n5d3H0c
https://s.apple.com/dE4z2d0E1w “
“As you guessed, the keystrokes for Target Display Mode will no longer work. Instead, please review these helpful guides to understand your external display options:
https://s.apple.com/dE9n5d3H0c
https://s.apple.com/dE4z2d0E1w “
Hrm... I have an older 2011 iMac running High Sierra that I still use for Target Display Mode. Works fine on my Intel (2019 16") MacBook Pro running Big Sur with a TB3->TB2 adapter, does *NOT* work on my new M1 Mac Mini. Cmd-F2 never switches to TDM, although System Information does show the Mini connected (I didn't test if Thunderbolt networking worked, but I don't know why it wouldn't.)
Same as mine - worked on 2015 MBP/Big Sur, but not on M1 Mini. So, it must be an M1 Apple decision - not Big Sur.
So is it now confirmed that there is no way to run an M1 Mini in TDM even to a 2009 27" iMac that doesn't use TB?
My iMac is on High Sierra so that shouldn't be an issue.
I was considering this as an option instead of buying a new monitor for an M1 Mini.
My iMac is on High Sierra so that shouldn't be an issue.
I was considering this as an option instead of buying a new monitor for an M1 Mini.
I’m in the same boat. Not being able to use the newer iMacs as displays for PCs is the main reason I’ve not upgraded from my 27" late 2009 iMac. It’s just so...useful! If I can’t connect the new Mini to it either, it is a strike against upgrading my MacOS platform.
I could be wrong, but I don't think anyone has "confirmed" that a Late 2009 27" iMac, or any of the Target Display Mode capable iMacs with the Mini Display Ports will not work with the M1 Macs.
I don't know why they wouldn't work with the M1 Macs, as the Mini Display Port iMacs are basically used like an external display.
The OP had the wrong OS installed, which is what I suspect is the issue. The the OP installed High Sierra, I bet it would work fine.
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Has any one found a way to connect a Mac Mini M1 to an older Imac running High Sierra. I am looking to do this with my imac 2011 and seeing the answer is no at https://support.apple.com/en-us/HT204592 . However none of the other webpage discussions have talked about using a HDMI connection.
Unfortunately there is no direct way to connect these devices together to use the iMac as a display.
I also have a M1 Mac mini and 2011 iMac running High Sierra.
There’s a couple of workarounds, but none are ideal:
1, Use ‘Screen Sharing’ to remotely connect to the M1 Mac mini from the iMac. This is ok but there is some stuttering and delay.
2, I’ve ordered a Luna Display USB-C adapter, which will plug into the M1 mini. This should work in a similar way to 1 above but hopefully with less delay.
3, The nuclear option - buy a driver board, which connects directly to the LCD panel of the iMac and turns it into a monitor with HDMI and displayport inputs. This would require complete disassembly of the iMac, meaning it would no longer be a functioning computer and requires some work to connect. Essentially you remove the computer parts from the iMac and install the driver board in place, turning it from a computer to a monitor. Risky but potentially the best option to turn the iMac into a display for the mini.
The opposite. I think the patched version of high Sierra on my 27” iMac meant there was no target display mode. I needed to revert the old iMac to an earlier OS. I sent the mini back.
Deccr (or any other wise soul): I have a couple of basic questions that I would love your follow up on:
1, Use ‘Screen Sharing’ to remotely connect to the M1 Mac mini from the iMac. This is ok but there is some stuttering and delay.
How are you sharing the screen from your new Mac Mini to the old iMac 2011?
2, I’ve ordered a Luna Display USB-C adapter, which will plug into the M1 mini. This should work in a similar way to 1 above but hopefully with less delay.
The Luna comes with software and costs $79. Do you know if the Luna app is required or can similar connectors available on Amazon, etc. work as well?
1, Use ‘Screen Sharing’ to remotely connect to the M1 Mac mini from the iMac. This is ok but there is some stuttering and delay.
How are you sharing the screen from your new Mac Mini to the old iMac 2011?
2, I’ve ordered a Luna Display USB-C adapter, which will plug into the M1 mini. This should work in a similar way to 1 above but hopefully with less delay.
The Luna comes with software and costs $79. Do you know if the Luna app is required or can similar connectors available on Amazon, etc. work as well?
Screen Sharing works over your network, it’s pretty straightforward, but there will be some latency depending on your network.
On your Mac Mini go to System preferences -> sharing -> and enable Screen Sharing
Then, on your iMac, open up finder. Within network, located on the left sidebar, you should see your Mac Mini.
Click on the entry for your Mac Mini and on the top menu bar you should see Share Screen. Click on this and a prompt will ask you for your username and password, which are the ones you use on your Mac Mini.
Do that and you should now see your Mac Mini mirrored on the iMac.
This of course assumes you have a display to connect your Mini to in the first place, otherwise you won’t be able to enable Screen Sharing on it.
Yes, I have a dummy HDMI dongle plugged into the mini - to emulate a display which allows for screen sharing.
The Luna Display app is free - you are paying for the hardware (either a USB-C or Mini DisplayPort dongle). It was originally designed to remotely use a Mac from an iPad. After they got sherlocked by Apple - with Sidecar - they expanded into Mac -> Mac screen sharing.
I’ll report on the Luna Display when it arrives, although I’m sure there’s plenty of info on YouTube.
Of course the easy answer is to buy a new monitor. But it would be nice to continue using the iMac display.
I’m still tempted to teardown the iMac and use the LCD panel as a monitor but it is an extreme answer.
The Luna Display app is free - you are paying for the hardware (either a USB-C or Mini DisplayPort dongle). It was originally designed to remotely use a Mac from an iPad. After they got sherlocked by Apple - with Sidecar - they expanded into Mac -> Mac screen sharing.
I’ll report on the Luna Display when it arrives, although I’m sure there’s plenty of info on YouTube.
Of course the easy answer is to buy a new monitor. But it would be nice to continue using the iMac display.
I’m still tempted to teardown the iMac and use the LCD panel as a monitor but it is an extreme answer.
Thank you all for the info. Youtube shows interesting ways to use the old iMac as a secondary screen (probably a good deal more as well).
Ok my Luna Display turned up today, along with the OWC Thunderbolt 4 Dock I ordered - perfect timing!
I’ve got to say I’m very impressed with the Luna Display.
I plugged it into the OWC Dock, attached to my M1 mini, and it automatically updated the firmware for the USB-C dongle. Once the software was setup, I opened the Luna Display app on the iMac and voila!
It’s definitely the best option I’ve found lag is non-existent compared to using screen-sharing and image quality is very good.
I even got audio working by using some old software by Rogue Amoeba - called LineIn. You need a 3.5mm male to male cable, with one end plugged into the mini and the other into the iMac mic-in/line-in port.
Luna Display uses DisplayPort to emulate a display, so any 2nd displays you want to use must utilise the HDMI port from the M1 mini or you’ll need a DisplayLink adapter for additional screens.
You can still use sidecar with a iPad, so I’ve managed to get all 3 screens working at once:
- iMac
- 21inch monitor (via HDMI)
- 12.9inch iPad (via sidecar)
For anyone who wants to keep using their iMac as a display I would highly recommend it.
If only Apple would re-enable Target Display Mode it would be perfect. Unfortunately I don’t think this will ever happen, so this is probably the next best thing - without tearing down the iMac to use the LCD panel as a monitor.
I’ve got to say I’m very impressed with the Luna Display.
I plugged it into the OWC Dock, attached to my M1 mini, and it automatically updated the firmware for the USB-C dongle. Once the software was setup, I opened the Luna Display app on the iMac and voila!
It’s definitely the best option I’ve found lag is non-existent compared to using screen-sharing and image quality is very good.
I even got audio working by using some old software by Rogue Amoeba - called LineIn. You need a 3.5mm male to male cable, with one end plugged into the mini and the other into the iMac mic-in/line-in port.
Luna Display uses DisplayPort to emulate a display, so any 2nd displays you want to use must utilise the HDMI port from the M1 mini or you’ll need a DisplayLink adapter for additional screens.
You can still use sidecar with a iPad, so I’ve managed to get all 3 screens working at once:
- iMac
- 21inch monitor (via HDMI)
- 12.9inch iPad (via sidecar)
For anyone who wants to keep using their iMac as a display I would highly recommend it.
If only Apple would re-enable Target Display Mode it would be perfect. Unfortunately I don’t think this will ever happen, so this is probably the next best thing - without tearing down the iMac to use the LCD panel as a monitor.
Luke Miani went the whole way and turned a 2011 27 iMac into not only a display but a full M1 iMac mini - by tearing down and installing the M1 mini inside the iMac enclosure:
9to5mac.com
YouTuber creates 'world's first' Apple Silicon iMac using M1 Mac mini parts [Video] - 9to5Mac
While we wait on Apple to release the first Apple Silicon-powered iMac sometime this year, YouTuber Luke Miani has taken...
9to5mac.com
Apple TB3 to MDP do not work and I have the same problem with an Apple (by Belkin) HDMI to MDP 6 ft cable (do not work ) I use a Mac mini M1 2020 Big Sur and a 27'' iMac late 2009 Higt Sierra as a display in target display mode. Both adapters/cable ar Apple branded (sold in an Apple store and suggested by Apple tech...!). I returned both. I assume this may by a combination of Mac OS support and connectivity (unidirectional ??)
Have you tried the actual $49 Apple TB3-TB2 adapter?
I currently use that on my 2011 Apple 27" TB display with my 16" MBP.
When I get my M1 Mini, I'll be testing on both a 2008 Apple 24" Cinema display using the adapter along with a HDMI 24" display (dual displays).
I have a 2011 27" with TB port that apparently won't work with TDM and a new M1 Imac.
The website for the Luna display claims that you can physically connect the two computers over an ethernet cable and it will work. Has anybody tried this?
Basically, I want to get the new M1 Imac but I know I will need considerably more screen real estate. This would allow me to repurpose my 2011 and avoid the expense of a new monitor or a more expensive "Big Imac" whenever those get released.