Does Catalina support Target Display mode?

I waited a while to upgrade to Catalina, I now find that Target display mode is not working - My 2017 iMac running v10.15 no longer displays to my mid 2011 iMac running 10.13.6. When I cmd f2 to launch the display of my 2017 to 2011 nothing happens. I have rebooted both, unplugged the thunderbolt cable (inc Adaptor - all Apple) still no luck.

Any ideas?

FWIW. I have been following this post and found that what users have experienced vs. what Apple says supports TDM seems to be in conflict. Apple is stating that to use TDM, a device needs to be running OS X 10.6.1 (Snow Leopard) or later. It doesn't mention anything about issues using this mode with the macOS series. Of course, anything is possible.

The other thing that appears to conflict is which exact iMac models are supported. The article states only three specific model can be used as displays. Yet, a number of replies in this post infer that a Mid 2011 model works, which is not one of those Apple listed. Even the "Questions for" section of this support article conflicts with the article's requirements as well. Go figure!

Ref: Use your iMac as a display with Target Display Mode - Apple Support

To spare anyone tedious scrolling, here's the answer:

The simple answer is NO.

Target display Mode only works on High Sierra or Lower (although in my case, it worked on Mojave and vanished after I updated to Catalina)

The article is: https://support.apple.com/en-au/HT204592 and the following is stated:

"Target display mode requires macOS High Sierra or earlier. It does not work with macOS Mojave or later".

Furthermore the article states: This article has been archived and is no longer updated by Apple.

No. Below is my config.

Used as a display:

• iMac 27-inch, Mid 2011
• macOS High Sierra 10.13.6

The host computer:

• iMac 21.5-inch, Retina 4K 2017
• macOS Catalina 10.15.1
• With clean install to an older version than upgrade it to Catalina

Connection:

• Thunderbolt 3 (USB-C) to Thunderbolt 2 Adapter
• Apple Thunderbolt Cable (2.0 m) - White

Make a backup or two, clone your boot storage to a scratch test environment, boot that, and upgrade and test that.

And is it wise to perform a production upgrade to Catalina, absent some Catalina-only requirement? Without testing?

Then let us know which (presumably) iMac you have, and whether it works with Target Display Mode. Or what (else) breaks.

We’re all still sorting out what works, and what doesn’t, and what works differently, based on the churn here in ASC.

~60 different questions either new or new replies in the past ~hour, mostly Catalina problem reports.

Thanks for the update and good to hear you you got it to work.

Just wanted to ask before I try upgrading... what OS are you running on the iMac?

(I've got a mid 2011 iMac which can only be upgraded to High Sierra and a MBP I'm hoping to update to Catalina).

I have a 2011 iMac and I use it daily in Target Display Mode with my 2014 MBP. It continues to work now that the MBP is running Catalina. (The iMac remains at High Sierra which the furthest it can go).

I don’t know if this is dependent on models, or if the tb3-tb2 adapter causes any difficulty. Just wanted to confirm that the 2011 iMac works for TDM.

All I know is that I could use TDM on a daily basis without any issues, I then upgrade to Catalina after reading that other users have had no or little issues, so took the plunge to find that my workflow is now considerably suffering due to TDM no longer working as it should. I suspect that the launch of SideCar has had a random impact on TDM. Maybe an update will fix this error?

I'm pretty new to all this, so maybe stating the obvious, so apologies if so, but anyway... when I first tried to set it up I read you just had to press cmd+F2 but later discovered that this only works at the log in screen and not once you've logged in.

Also it only seems to work using my official Mac keyboard and not my Logitech one.

No, I am not really interested in using an iPad as a second display, as it is too small. My set up is as follows...

Main Mac - 2017 21.5" Catalina V10.15 - Connected to....

Display Mac - Mid 2011 21.5" High Sierra V10.13.6

Using Apple Thunderbolt 3 (USB-C) to Thunderbolt 2 Adapter

This has always worked up until the Catalina upgrade. The main Mac user logged in, the display mac user logged in - press cmd f2, wait a second or 2 and I have an extended display. Now nothing, not even a flicker.

Interesting - It has always worked with both mac users logged in, I don't think I ever tried it at the login screen. I also note the comment about the keyboard. My Wired keyboard to the 2017 iMac ceased working a short while ago, the only way I could get it to work was plugging it in to a USB extension lead, all was then good.

I'll do some further testing with and without the USB extension, and whether being logged in or not makes any difference. I'll report back my findings.

Ok, After a bit of testing - Keyboard still does not work without the extension lead (annoying but I can live with it) tried all scenarios still no go. Tried the same set up using my wife's MacBook Air running Mojave still nothing.

Then it dawned on me - You use the target display keyboard to press cmd f2 NOT the main display keyboard.

Stupid Me!!

Works a treat.

Sorry for wasting all your time.but thank you for contributing

Macbook Pro - 2017 Touchbar Catalina V10.15 - Connected to....

Display iMac - Late 2013 27" Catalina V10.15

Using Apple Thunderbolt 3 (USB-C) to Thunderbolt 2 Adapter

I have been speaking to apple support both in store and on the phone, not very helpful over the phone especially giving steps on SMC... Holding Shift+Ctrl+Option 10-30sec safe mode etc. Even with SMC reset, CMD+F2 didn't help. I'm contemplating formating my iMac and downgrading back to Mojave to see if it helped. Previously it worked fine

I am using iMac 27-inch, Mid 2011 (macOS 10.13.6) as a display and the host machine is iMac 21.5-inch, 2017. I am using the "Thunderbolt 3 (USB-C) to Thunderbolt 2 Adapter" and the "Thunderbolt Cable (2m)" bought from Apple Store.

It works when I am using macOS Mojave 10.14.6 but not works after upgrading to macOS Catalina. I already tried many methods, but still not works.