Target Display Mode not working 2020 MacBook Pro (Catalina)

2020 MacBook Pro DOES NOT support Target Display Mode. The feature has been deliberately REMOVED form the computer's ROM, is now Unsupported, and can Not be made to work, at all, ever.

—Target display mode not working, I want to set up an old iMac (mid-2011 running High Sierra) as an external monitor for my new 2020 MacBook Pro (running Catalina)...I am using a brand new 2020 MacBook Pro, USB-C to Thunderbolt adapter, Thunderbolt cable, plugged into the iMac's Thunderbolt port (not mini display).

The support article on TDM that Grant links says this:

—I am quite unhappy that this appears to be apple purposefully rendering old products obsolete by not including backward compatibility software/code.

Tell Apple: Feedback - macOS - Apple

—Will apple fix this in a software update?

We are not Apple but end users like you. Based on the fact that Apple started the deprecation of Target Display Model in Late 2014 and completed it early this year, I would say "chances are slim."

I think all the confusion over TDM was a lack of journalistic research, and not a plot by Apple. Prior to COVID we saw 1-2 posts a MONTH about TDM. Now we see a dozen or more a DAY. I believe some overzealous journalist saw a quarantine opportunity and posted about TDM as an option for people working and from home, but forget to look up the sysreqs and history that would show TDM is a dead issue.

let's clear somethings up once and for all:

TargetDisplayMode to any Mac works with (from) any Mac or PC as host device, so long as it's not Thunderbolt on the first mac.

Any Mac with Thunderbolt 1/2/3 AND TargetDisplayMode will only work with Macs and Pc’s of similar standing, so TB1 to TB1, TB2 to TB2 etc, because of the way that Thunderbolt works, backwards compatibility or forwards compatibility, display-wise is not something you should rely on when buying a new Mac hoping to use an old Mac as display.

I won't go into to much detail as to why it won't work, but suffice it to say it's because of the way Thunderbolt works and in the manner it's able to carry certain protocols to and from computer to displays such as HDMI, DVI, DisplayPort etc. and because of this interplay and such things as HDCP requirements it may and may not work with the plethora of diverging setups ya’ll got out there.

Now, onto what DOES work in regards of Target Display Mode:

All Macs of any year that are able to connect over Thunderbolt, HDMI, DisplayPort (likely mDP) or DVI (likely mini-DVI) are able to send video out to any older iMac or MacBook without Thunderbolt BUT with a HDMI, DVI or DP connector.

So the following scenario/example, from my setup goes:

A 2020 MacBook Air/Pro M1 or 2020 Mac Mini M1 to an 24-inch iMac 2008 using Mini DVI and iMac 27 inch 2010 with Mini DisplayPort.

In both of these cases, such an older iMac, when booted up and logged in to macOS, can be set to TDM using cmd+F2 on the keyboard (of the Mac you are going to use as a monitor), at that time, such a Mac will present itself as a vanilla DVI or DP monitor to any host computer, in my case those M1 Macs. All you need to do is provide the proper cable and adapters to connect them, in my case a DisplayPort to Mini DisplayPort cable (with bi-directional support) that goes into a caldigit TS3 Plus dock, which has a standard DisplayPort connector on it.

At that point, the TB3 that comes out of the Mac is first passing through the dock, and then it will provide the DisplayPort signal. of course direct connection is also possible, you just have to find the right cable for it, most likely a apple or belkin type branded tb3 usb c to either hdmi, DisplayPort, dvi, etc cable whichever you need to connect that TDM mac's port to it. But it does work.

Again, so long as the Mac you want to use as a display didn't have any version of thunderbolt shipped with it, because then, as explained above, you're gonna run into connection issues as Thunderbolt will be the limiting factor in interoperability.

I hope this helps for others. AS far as my setup is concerned, the iMac screens I'm using are both fully recognised, with the right color profile etc, and on the 27 inch iMac with the mini Display port connector, it even sends the audio along to that mac's built in speakers if I want to:

Color LCD* is how my 2010 27 inch iMac appears in the audio prefs pane

...and as just 'iMac' under my display prefs panel.

(*Which I rarely use, most of the times, I use the SPDIF to send the audio to Sonos for surround experience or in this case just using headphones)

Also currently the 2008 24 inch won't turn on anymore, but before that it was connected tot my M1 Mac mini using an apple adapter which gives a mini dvi connector, this setup won't carry audio though, as it was not part of apple's mini dvi implementation on those Macs at the time)

According to what Apple Support told me today after some tests with them (and chasing them for a couple of weeks), Target Display Mode does NOT work with MBP 2020 13'' + iMac 27'' late 2013. They kind of apologized for the misleading information on their website (I really looked this up before purchasing the MBP), so I don't think that there will be any fix in the future.

After spending hours troubleshooting with Apple Support to address this exact same issue, it turns out the feature is only supported for 2019 MacBooks and older. In this article https://support.apple.com/en-us/HT204592, last updated in April 2020, they exclude the 2020 models: "You can connect any of these older iMac models to another Mac from 2019 or earlier for use as an external display." No proper reason given, only "We apologize for the inconvenience", and "This is how the market works" responses.

No, nothing has changed with regards the iMac compatibility. It's that MacBook Pros and MacBook Airs (ie, the source machines for Target Display Mode) from 2020 aren't supported.

I've been on Apple Chat - they were lovely, but didn't know about it. When they found out the details they explained that it is an OS issue. And I asked if I could load an older OS on my MacBook 13" 2020. She said that would, in theory, fix the problem but it's not possible to run a MacBook on an OS older than the one it comes with.

But if it's true that Apple have just written Target Display Mode capability out of the OS, why are machines that are 2019 or earlier still working in TDM when their OS is updated?

I've just had to put my iMac up for sale because it's completely useless to me now. And send the Apple cables back. Not at all pleased.

I have exactly the same problem. I want to use my IMac mid 2001 27 inch (MacOS High Sierra) as a target display of my new macbook pro 13' 2020 (MacOS Catalina).

I always used the Imac 2011 as the target display of my macbook 2014 and worked fine through a thunderbolt cable!

Now, with the macbook pro 2020 I bought the Thunderbolt 3 to thunderbolt 2 adapter hoping to use the Imac 2011 as the target display of the new macbook 2020. Nevertheless, after receiving the adapter I connected the two macs (the macbook 2020 with the Imac 2011) but nothing, when I press Command+F2 on my Imac 2011 nothing happen.

I called the Apple support and after 2 hours of trials they CONFIRMED that actually from macbooks 2020 onwards this functionality (IMac 2011 as target mode with the newest macbooks) is not supported anymore. So, the adapter is totally useless, this is why I am returning back the adapter to Apple.

I am quite frustrated and angry with Apple.

If someone finds a solution please let me know. Thanks!

One possible reason is that they wanted the space in the ROM for additional features, especially considering that the Apple-Silicon M1 Macs were being developed.

Apple does not add new features for products no longer for sale, and the last iMac that supported that feature was a mid 2014 iMac, discontinued October 2015.

ah it's been a while since I've posted here, I can say to start with: the cable in this case really matters, try a thunderbolt 3 to (mini) displayport cable and make sure the cable is marketed as bi-directional, most of the times, the cable is not bi-directional and this would prevent a connection and the necessary HDCP-handshakes.

As TDM in combination with Thunderbolt 3 or newer Macs has been a hot issue on here and elsewhere, which Apple still has failed to address, I can at least provide the following update from my perspective and setup, after which I'll reply to karinavans' specific issues.

But, suffice it to say if you have an {i}Mac with Thunderbolt you want to use as a target display for another Thunderbolt mac, you can't {in most cases} because of limitations of the DisplayPort and HDMI protocols when run over Thunderbolt. Only a small subset of such macs that shipped with first and second gen Thunderbolt might work OOBE with similar class macs.

Now IF, and I stress IF, you like me are lucky to still own a pre-Thunderbolt-era Mac with built-in display that either uses Mini DVI or mini DisplayPort as is the case with my 2010 27'' iMac, then yes, you can indeed use the screen as a display for other macs, even other non-Apple computers (really**), as it would present itself just as a vanilla generic DVI or DisplayPort monitor with digital audio path (in the case of mDP Macs) to any computer upon activating TDM from the active, running copy of MacOS on that mac.

So a fully working mac (with built-in display) with a valid install of whatever version of macOS it happend to ship with or later version it still support, is indeed needed, also in most cases, you won't have to login on the mac you want to use as a display, just make sure the mac is fully booted up and on the login screen, when you want to active TDM with the official keyboard command.

So keep that mac around if you ever switch to a macbook :_)

Now to re-cap to karinavans' issue, as I've stated above, the cable really matters, because most of the failures come from the cable not being manufactured up to snuff. And yes, the cable has to be marketed as bi-directional.

For my specific setup the dock is the Caldigit TS3 Plus, which has it's own Thunderbolt chipset and comes with a native DisplayPort connection, that is connecting the iMac to the MacBook, the cable used is the Rankie Mini DisplayPort (Mini DP) to DP-Cable as sold on Amazon. this setup works as you can see in this photo:

(the monitor on the right is not in use with the Macbook, but rather connected to an ISP's tv settopbox via hdmi, photo is recent, dated 23rd of May)

I hope this clarifies things for everyone here.

You can spot a bit of the TS3 on the left, behind the macbook's display.

Television feed on the iMac monitor is coming from a USB DVB-C tuner stick connected to the caldigit dock icw Eyetv software.

The answer, as noted above, is that Target Display Mode with old iMacs is not supported in the 2020 models.

Apple had the opportunity to fix the software when users complained. The "newest" iMac supported by this feature is a 2014 model, which is about to go unsupported. They opted to declare the entire process "no longer supported" and amended the Documentation to reflect that change.

The last supported iMac was the 2014 model. That is getting old. Odds are not good that this feature will be seen in any future product.

Luckily, modest displays that can do the job are getting really cheap by historical measures, or HDTV set can be used. Or use your iPad is "Sidecar" mode.

dagmarpiano71 wrote:

• Just a theory here - but maybe if you have a USB HDMI capture device you can run a a cable from your MBP to your iMac. So the signal would go:

MBP USB-C output to:

• USB-C to HDMI adapter to:

• HDMI cable to:

• HDMI capture device plugged in to:

• iMac

Then you'd run the capture stream full screen

Based on Apple articles and the way Mac display interfaces work, that "solution" does not have a prayer of working "just with cables". it requires stunt-box with the equivalent of a display interface inside it. Pricey.

That proposed solution could only work with a special-purpose Video capture device. That money would be better spent on a new display.

I found this option that can be used to connect old Macs to new Mac over WiFi - Astropad Luna Display

It professes to work in Mac to Mac mode with display source Mac from 2011 or later, and display target Mac from 2007 or later. It support Macs with Apple M1. It also allows iPad to Mac mode which looks nice especially for using an Apple Pencil for drawing.

It is over WiFi so I imagine it isn't great for gaming, and maybe not for video editing - however they claim 16ms latency.

At $80 it is a bit more expensive than cables, but much cheaper than additional monitors - and its also pretty tidy to go wireless.

I haven't tried it myself (they don't currently ship to the UK because our import processes are a mess right now) but thought others here might find it useful.

as noted earlier, Target Display Mode has been deprecated and is not supported on MacBook Pro after 2019 models.

I decided to upgrade my 2018 MacBook Pro 13" to the new 2020 MBP 13" basically for the new keyboard and 32GB memory. My setup at my office was to connect my 2018 MBP with thunderbolts to 2 iMacs, late 2012 and late 2013, both 21.5in and both updated with Catalina with TDM (CMD+F2). When I received my new MBP 2020 to my great disappointment I discovered that Apple, in their wisdom, took away the Target Display Mode TDM from the new 13" MBP 2020! I am a FANATIC Apple products buyer but in this case I fail to understand the logic behind this decision. Of course if I want to have these two screens I will need to continue working with my 2018 MBP OR buy two new monitors and connect them with HDMI cables to my new 2020 MBP 13". Is this what Apple want us to do? I don't think so!!! I will appreciate an answer....