Rudolf from Switzerland asked me if he could use his 10 year old iMac as a monitor for one Mac mini 2018 he intends to buy. Since this question is also interesting for other Apple users, I have prepared the relevant information as a contribution. Because not only the Mac mini, but also the MacBook Pro / Air can theoretically be coupled with the iMac via screen synchronization for extended display. How to do this and what requirements must be met, you will read in the following.

An iMac as an external monitor for Mac, Mac mini, MacBook and Co.? That is possible - but there are some requirements. You can find the instructions here! (Images: Apple)

An iMac as an external monitor for Mac, Mac mini, MacBook and Co.? That is possible - but there are some requirements. You can find the instructions here! (Images: Apple)

Using the iMac as a monitor - requirements

There are certain prerequisites and system requirements that must be met so that the iMac can be used as an (external) monitor on a Mac, Mac mini or MacBook. In the following list I have put together the compatible models for you. Because not every Apple iMac is made for screen synchronization mode:

  • iMac end of 2009 27 "
  • iMac mid 2010 27 "
  • iMac mid-2011 to mid-2014

iMacs from the end of 2014 with 27 “and 5K retina displays cannot be used. In addition, it must be ensured that the above models have Mac OS X 10.6.1 or a newer version of macOS, but may have a maximum of macOS High Sierra. The more recent macOS versions (Mojave, Catalina, Big Sur) no longer support the target display mode. You also need a keyboard that plugs into the iMac - the original model is best.

Old Apple iMac as a screen extension - cable

So now you already know which Apple computers are required with which operating system and which peripherals. But of course the image source, i.e. the new computer, and the model that is stored as a display have to be connected. The connection can be established using Mini DisplayPort cables and Thunderbolt cables as well as a combination of the two. Here is an overview:

iMac that is used as a monitor Cable for the monitor function Connection to the other Apple computer
iMac (27 ″, late 2009) Mini DisplayPort to Mini DisplayPort
(on Amazon)
Mini DisplayPort or Thunderbolt
(on Amazon: MiniDP / TB3)
iMac (27 ″, mid 2010) Mini DisplayPort to Mini DisplayPort
(on Amazon)
Mini DisplayPort or Thunderbolt
(on Amazon: MiniDP / TB3)
iMac (mid 2011 to mid 2014) Thunderbolt
(on Amazon)
(on Amazon)

Source: Apple Support Document HT204592

The old iMacs usually have the mini display port (left in the photo), while the new Mac models have USB-C ports (right). The two options listed below should provide the right connection here (Photo: Sir Apfelot).

The old iMacs usually have the Mini-Displayport / Mini-DP (left in the photo), while the new Mac models are equipped with USB-C ports (right). The two options listed below should provide the right connection here (Photo: Sir Apfelot).

Update 12.12.2020/XNUMX/XNUMX: Mini-DP to USB-C solution

If your Macs have the sockets shown above, then I have a combination of cable and adapter for you that works with a high degree of security. A reader (thank you, Robert!) Wrote to me that he is using an old iMac late 2009 on the Mac Mini 2018:

From the two products you put together an adapter cable that should also do its job for you. You may not have to read any further in the article, because there are other solutions below that did not work for all readers. But I still want to leave it in here as a backup.

Warning: some USB-C to DisplayPort cables do not work

As a reader recently wrote to me, the connection between iMac and MacBook Pro is not working. He used a cable that fits into the iMac (DisplayPort) and the MacBook Pro (USB-C), but it still doesn't work.

At first I thought it was because the cable is not a Thunderbolt 3 cable, but it seems that there are also USB-C to DisplayPort cables that do their job. So there is still a little trial and error. I've listed both variants here. Once the solution with the Apple Thunderbolt cable and adapter and once a USB-C to mini Displayport cable, which according to a reader (see comments below) works for him where the Apple solution has failed:

1st option: Thunderbolt adapter and Thunderbolt 2 cable

2nd option: USB-C to mini DisplayPort cable

I would recommend ordering both and then keeping the solution that works. The other cables or adapters can then be sent back to Amazon.

Activate screen synchronization mode - Here's how

If you have both Apple computers connected with the correct cable, both are connected to a power source and switched on, and the old iMac has a keyboard, then you can start. Just follow these steps and nothing should stand in the way of using the old computer as a monitor:

  1. Connect both computers together and turn them on
  2. Leave iMac on the login screen
  3. Log into a macOS account on the other computer
  4. Press cmd + F2 on the iMac
  5. If that doesn't work: press cmd + Fn + F2

Also interesting: “Keyboard shortcuts for the Mac” book tip

Troubleshooting - If it doesn't work right away

Points 4 and 5 are listed as alternatives, as the menu item “Use the F1, F2 etc. keys as standard function keys” could be activated in the system settings of the secondary device. So if the combination of Command and F2 doesn't work, just try the alternative. In addition, this shortcut has to be pressed on the keyboard that is connected to the secondary computer - pressing it on the Mac mini, MacBook or other connected computer does nothing. In addition, the problem could be with an Apple or third-party keyboard that is too old. It is best to use the keyboard that came with the iMac.

It is also essential that the secondary computer is in the macOS login window. No user account must be open or any version of Windows running through Boot Camp. In addition, the primary Mac must be logged into a user account. If that still doesn't work, it can help to connect a “real” external monitor first and then try the iMac again. Using older iMacs as monitors is generally a better idea, because the color fidelity and sharpness of the displays (even if they are not yet 5K Retina displays) have already been impressive.

Update 18.03.2021/XNUMX/XNUMX: Use iMac as a PC display?

Yes, that should work too. In the comments below, I sometimes made different claims because I didn't know any better at the time, but it is correct: You can also use an iMac as a monitor for a Windows laptop or desktop computer. The prerequisites and the procedure are as described above.

Answer to Rudolf's question - Yes, it should work!

If the old iMac is one of the above models and connect it to a Thunderbolt 3 (USB-C) to Mini DisplayPort cable is used, the new Mac mini 2018 should be able to successfully transmit video and audio signals. By the way: The linked cable should be perfect for this; a customer review (in English, but at least detailed) says the following:

I am really excited about this because it was very difficult to find the right cable. I have just received the cable USB C to Mini DisplayPort to connect my Mac Book Pro 2017 with touch bar with my iMac (middle 2010) to use it as a monitor. It works perfect !!! It saved me from buying a new Monitor or a new iMac.

Apple iMac as a monitor - questions and answers on the subject

If you don't want to buy an extra screen for your new Mac, Mac mini, MacBook or another iMac because you still have an old complete computer from Cupertino, I hope that this article was able to help you. The connection can be established quickly via Thunderbolt 3, Thunderbolt 2 and Mini DisplayPort and the screen synchronization mode can be used. If you have any questions, tips or tricks on this or related topics, please leave a comment!

Do you like my blog? Then I would be happy to receive a short review on Google. Easy leave something here for a moment - that would be great, thank you!


  1. Robert says:

    Interesting topic - that's exactly how I do it: a Mac mini 2018 on an iMac 27 ″ late 2009. It works - almost - without any problems.
    It's actually just inconveniences that have to do with the brightness control in particular: when switching to the mini, the brightness on the iMac is always at its maximum, so my eyesight cells are almost blown out. Then you have to regulate the brightness down using the function keys on the iMac keyboard. There is no onscreen feedback. When switching back to the iMac, the brightness is then minimal, then I have to turn it up again.
    Well, inconvenient, but I'm happy that my iMac does this job well, because it can no longer Mojave (but remains my workstation, the mini with Mojave is only developed).
    Oh yes, one more annoyance: if the mini wakes up from sleep without motivation, the iMac screen switches automatically.

    • Sir Apfelot says:

      Hello Robert! Thanks for the info. These are of course small losses in terms of comfort ... I think you have to put up with that when you use such an old iMac as a display. : D But I honestly didn't know that there were the restrictions. So I'm glad you mentioned them here!

  2. Heinz Hügli says:

    All well and good. But how does that work with an iMac 24 inch in mid-2007.
    Help would be great….

    • Sir Apfelot says:

      Hello Heinz! Unfortunately only the 27 inch iMacs have the "Target Display Mode". Without it, it won't work as a second monitor. :(

      • Thomas says:

        Hello! I use my iMac (20 inches, mid-2007) as a display for my MacBook Air (2018) via Airserver (, approx. 17 euros, trial version for 2 weeks). The program is installed on the iMac and controlled by the MacBook via AirPlay. There are, of course, restrictions on the resolution. At least Mac OS X 10.9 is required.

  3. Wolfgang Stanik says:


    I can't find a cable anywhere, Thunderbold on sisplayport.
    Can you tell me where I can get it, right? i think wrong.
    Thanks for an info

    • Sir Apfelot says:

      Hello Wolfgang! It would be important to know which Thunderbolt version (1,2, 3 or XNUMX) and which display port (mini-DP or normal size). Can you maybe add that? Thank you!

  4. Robert says:

    I hung a USB-C to DP adapter on a DP cable. Not nice, but it works.
    At Amazon, for example (editor's note: the link was unfortunately not complete, so I added a link to a suitable adapter):

  5. chris says:


    A very interesting article. I am facing a situation similar to what you can read in the comments here. My iMac 27 “(2011) has reached the end of the macOS flagpole. I would like to continue to use this iMac in its current state, but also have the latest macOS available. I'm considering getting a Mac mini and using the iMac as a display. This seems like a viable option.

    However, I would like to be able to use the iMac's keyboard and mouse to work with the Mac mini after switching to display mode.

    Unfortunately, I was unable to find an answer to this question during my research. - So this can work this way, or do I have to use a keyboard / mouse attached to the Mac mini.

    Thanks in advance for an answer.


    • Sir Apfelot says:

      Hello Chris! So basically you can of course pair the iMac keyboard and mouse with a Mac Mini, but not at the same time. That means they will only work as an input source for the Mac Mini. If you are looking for something that you can use with both Macs at the same time, then I would give you the Satechi Slim Wireless Keyboard recommend. You can pair these with several Bluetooth devices and then switch back and forth between them at the touch of a button.

      Logitech also offers a keyboard and mouse set that can be paired with up to three devices: Logitech K375s and M720. This could also be something for you if you want to operate both Macs at the same time. I hope this answers your question and I didn't get you completely wrong. : D

      • chris says:

        Hello Sir Apfelot,

        Thank you for your answer. You got me right I just want to use the processing power of the Mac mini and keep the existing peripherals as they are. If that works, I am satisfied and would want to use this solution. - However, an optimal solution would have been if the “external” Mac could have been opened via a window and switched back and forth similar to “Parallels”. Unfortunately, you can't have everything ...

        Now I have read on other websites that you have to be logged in with an account on the external Mac in order to establish the coupling. This complete establishment of the connection is not entirely clear to me. Is there already a thread on this?

        According to my current understanding, it is not possible to switch back and forth between the two computers, because if you disconnect the connection, according to other comments, the computer that fulfills the screen function should remain dark. So keyboards and mice that can be switched over would not be a remedy. But maybe I didn't understand everything either.

        The subject is complex and if you want to explore everything before investing in hardware, it is difficult. You can't test anything.

        Alternatively, I could get a new iMac. In terms of price, you get to comparable regions. You just have to have the space on your desk to be able to place both devices.

        Conclusion: As a decision-making aid, it would be helpful for me to know how the startup procedure of the two computers has to work.

        A completely different approach would be to connect the external computer via VNC. But here, too, I am faced with the problem of how to start this configuration without having first started the system with the keyboard and mouse on the external computer.


        • Sir Apfelot says:

          Hello Chris! You started several questions in your comment. I'll try to do it one by one:

          1. Switching back and forth between the iMac and the Mac Mini does not work when the iMac is in target display mode. To do this, you would have to reboot it, which is very cumbersome.

          2. Personally, I would choose the variant and get a new iMac, because the old iMacs do not have a retina screen, which of course makes the display much worse. I haven't quite understood why you would have to have both iMacs running in parallel. What can the old iMac do that the new one can't ???

          3. A guide for pairing? You have just landed on the relevant article you are commenting on. : D

          4. The solution via VNC is possible. I would then set the iMac so that it boots without login and starts VNC directly when the system starts. Then you can access it directly from the other Mac even after restarting and you don't need a keyboard and mouse on the iMac to log in. The configuration is very simple ...

          I hope I have answered your questions!



    • Robert says:

      Hey Chris,
      I also hoped to get by with just one keyboard, so I tried a software solution (unfortunately I can't remember the name of that).
      However, all attempts did not work. When the iMac is in Target Display mode, the keyboard sharing software can't handle it. This keyboard only works as a brightness regulator and as a toggle switch.
      I made use of a second keyboard and mouse that were lying around in my pool.

      What also works (for smaller uses): Use screen sharing. This also allows you to do copy / paste between the systems

  6. Robert says:

    Maybe I hear a misunderstanding from Jens, so I'll describe my use of this combination of iMac late 2009 and mini 2018 again.

    You are completely logged in on both computers, otherwise there is no other way. It's not like Firewire Target mode, where the Mac is just a hard drive.

    I log into the iMac as normal. Then I switch the mini on using the power button, the iMac screen switches automatically, but the target display mode must have been used beforehand. I can't say exactly how it works the first time, but you always have to be logged in to the iMac first.
    Auto-login is active on my mini, but it doesn't have to be, you can also go through the login screen.

    In daily operation I use it like this:
    - The mini and iMac sleep, I wake up the iMac with the keyboard connected, normal work is possible.
    - Now I wake up the mini (e.g. via its power switch). The screen switches to the mini, with full brightness.
    - The keyboard and mouse on the iMac are "switched off", only the brightness keys (possibly together with Fn) and above all the shift combination still work (Command-Fn-F2).
    - There is no sound on the mini through the iMac speakers.
    - I use the mini with a second keyboard and mouse, both via Bluetooth.

    You can only return to the iMac using the keyboard on the iMac.

    What else is still possible: on the iMac (account) I start sharing the screen with the mini, on which I have previously approved it in the "Approvals" area. Now I can operate the mini completely with the iMac keyboard and mouse, of course with a certain loss of speed in the display. This is even possible full screen, for example on your own "desk". (Sorry, sometimes the terms may not be right, I run a lot of programs in English, because of developers and so on ;-)).

    You can also go to the iMac via screen sharing on the mini, it becomes almost pathological when the screen sharing is running again -> recursive chaos ;-)

    As far as my maybe a bit dingy explanation, please ask again.

  7. Robert says:

    Addendum: You can play sound from the mini through the iMac speakers, but not from both "accounts" at the same time. In the "Sound" settings on the mini there is a "Color LCD" output device of the "DisplayPort" type that you can switch to. Or you can use the built-in silent speaker on the mini ;-)

    • Sir Apfelot says:

      Hello Robert! Thanks for the detailed explanation. I wouldn't have known in detail because I've never used a Mac in this mode. : D

  8. chris says:

    Hello Sir Apfelot and Robert,

    I am currently on a vacation trip and have not yet been able to answer.

    Thank you for your comments, that gave me some clarity. Even if it is technically possible to operate a Mac mini via an iMac, there are many small peculiarities in operation. I agree with Sir Apfelot that it is better to get a new iMac. The savings in hardware are small and not worth it.

    "To the question, what can the old iMac do that the new one can't":

    I can't say for sure either, but it's a stable, running system. Second, I am reluctant to part with a Mac HW that I have worked with problem for many years. Maybe after I have gotten to know my new iMac and have been able to port all software without any problems, I will finally part with it. That is how long I will use both computers.

    Thank you again especially Sir Apfelot and I am glad I came across this website.


  9. chris says:

    Short correction:

    what I really mean is:

    ..with which I "problem-free" for many years ..

    but I think that came out of context.


  10. Skirt says:

    Hello, I'm a Mac layman and I'm currently stuck.
    I have an iMac late 2009 which I use with a patch ( Mojave is running stably.

    We then wanted to run a Macbook Pro (TB connection) on the iMac via a miniDP cable. According to Apple site and Internet as well as here describe possible. However, the Imac shows nothing when switching with cmd + F2. He tries to switch and briefly (less than a second) a black screen and then back the old image from the iMac. Tried everything: switch from the login screen, switch logged in, fn + cmd + F2 ..

    Strangely, the connection between Macbook Pro and a Dell monitor from TB2 to miniDP (monitor) with DP cable goes without problems.

    Also from the Imac miniDP to (monitor) with DP cable went without problems.

    Just do not stop Macbook to Imac does not want.

    I do not know whether I am making a mistake in thinking somewhere or something else I have to pay attention to.

    I would be happy to receive advice and suggestions.

    • Sir Apfelot says:

      Hello Saya!
      Thank you for your question. It should actually work if you have a 27-inch iMac. Apple's support document explicitly states the iMac late 2009 with 27 inches. Are you that size LG! Jens

      • Skirt says:

        Hello, Jens!
        Thank you for your prompt reply. Yes, this is an iMac late 2009 with 27 ″. The Macbook Pro is from 2015 (with HMDI if relevant).

        • Sir Apfelot says:

          Hello Saya! As Robert wrote, maybe it's just because you patched Mojave. This is difficult to clarify ... if you installed a macOS that is officially approved for your Mac, it could work. LG! Jens

    • Robert says:

      Hmm, since something happens at Fn + cmd + 2 at least shows that macOS recognizes something at the DP input, otherwise there is not even a short switch to black. But maybe he doesn't like the signal? Sorry, no idea, and trying to patch Mojave on my iMac late 2009 I will definitely not, because that could be the reason, right? ;-)

    • Robert says:

      Hi Saya,
      now I'm a little smarter again: it doesn't seem to be due to your Mojave patch, because I can't address the iMac screen of a 2015 MacBook Pro either. Like you, the iMac gets dark, but that's it. With my 2018 Mac mini as the source, it still works.
      Too bad, now I would have been happy about this solution, but I keep trying.

      • Skirt says:

        Hi Robert,
        that helps me a bit. Now the colleague wanted to connect his MacPro (source) to the Imac (DPmini) via an HDMI / DPmini adapter. Do not think it will work, but I'll take a look and report.

    • Robert says:

      I have just successfully displayed my new / used MacBook Pro 13 Retina from 2015 on the iMac 27 late 2009, as it should be!
      The trick: I tried the second Thunderbolt port. Plugged in and the iMac switched itself over. The iMac also switched to the other port, but only to black.
      I don't know if the two Thunderbolt ports on my MacBook are different, but it does seem so.

      • Sir Apfelot says:

        Hi Robert! Thanks for the hint. That is interesting. I think I've read that there are also differences in the charging current, depending on which USB-C port on the MacBook Pro 13 inch you plug the connector. With the 15 inch model there is probably no difference. But that might also be an explanation for your phenomenon ...

      • Skirt says:

        Hi Robert,
        did you use a Thunderbold cable or DPmini?

        • Robert says:

          I used a DP mini to DP mini cable.
          To my shame, I have to admit that I told nonsense above: one of my Thunderbolt ports was simply defective, which I only verified with a Firewire adapter. A tab in the port was bent and was causing the problem.

  11. Dear Sir,

    thanks for the detailed instructions. Do you know whether this is also possible with a docking station? Background: I have a fairly new MacBook Pro and a fairly old iMac 27 (Mid 11). The old iMac is now completely at the end. Now I would like to be able to plug in and unplug the MBP as easily as possible, i.e. use the iMac as a monitor and have a keyboard / mouse on my desk, then plug in / clamp / switch the MBP and continue working.

    Any idea?

    All good wishes

    Guido Augustin

    • Sir Apfelot says:

      Hello Guido!

      In principle, there is nothing wrong with doing it with a dock, as you say. It is only important that it is not a USB-C dock but a Thunderbolt dock, because the image transfer to the iMac does not work via USB.

      Here I picked out a few of the current TB3 docks:
      - ICY BOX Thunderbolt 3 Dock
      - Elgato TB3 Dock (Standard or Pro)
      - Belkin Thunderbolt 3 Docking Station

      What you use there is basically a matter of taste. All of them have a few bad reviews, but basically they should do the job for you.
      LG! Jens

      • Guido says:

        1.000 thanks, have the little IcyBox worried, runs flawlessly!

        • Sir Apfelot says:

          Yes, it works with that too. However, it is again one of the adapters that cannot handle 4K @ 60Hz. But if you don't play, but rather surf and use word processing, then you should only notice the 30 Hz if you move the mouse pointer quickly. But it's nice that everything works out for you! LG! Jens

      • Max says:

        Hello, Jens, that means with the ICY BOX IB-DK2102-C here ( it does not work…? But it can be read on the product description. I connected a new MacBook Pro 13,3 "to it (MacOs 10.15.4) and want to control my old iMac 27" (2011) monitor with it. With my old 15 "MacBook Pro it went wonderfully (without adapter) with cmd + F2, now with the Raidsonic adapter (MiniDisplayport on the adapter, Thunderbolt on the iMac) unfortunately not ... Does it have to be a Thunderbolt adapter?

        • Sir Apfelot says:

          Hi Mac, sorry for the late reply. To be honest, I can't assess it, but mostly such hubs between the Apple-specific connections tend to cause problems. The Apple SuperDrive also doesn't like it when a USB hub is clamped in between. Nobody knows why that is, but it doesn't work. But I don't have any experience with the Icy Box Dock.

          • Max says:

            Hello, Jens, unfortunately it really doesn't work - the dock doesn't let the protocol "through", which is necessary for the target mode - only works with a direct connection between MacBook Pro and iMac. Pity! And expensive (adapter ...; - /

          • Sir Apfelot says:

            Hi Max! I'm sorry ... but I thought so. Using the iMac as an external monitor is a very special thing.

  12. ingo says:

    Hello Sir,
    Apple says that the Thunderbolt2 on the iMac2012 also functions as a mini display port, can it also record a MiniDP signal for iMac monitor use?
    thank you greetings from Berlin

    • Sir Apfelot says:

      Hello Ingo! I'm not so sure. According to the table, your iMac from 2012 definitely supports the target display mode. However, the cable that you should use only says "Thunderbolt" and not a mini-DP cable. I would just test it in your place and, if necessary, return the cable if it doesn't work. It would be great if you would let me know so that "we" know if it works! : D

  13. Ksenia says:

    Hello Sir Apfelot,

    I have an iMac 27 ′, in mid 2011 with OS X Yosemite version 10.10.5, which I would like to use as a second monitor with a MacBook Pro Retina 15 ′, in mid 2015 with Mac OS X Mojave version 10.14.5. I have tried both a Thunderbolt to Thunderbolt cable and a Thunderbolt to HDMI cable and also with the help of the key combinations in the logged off mode. It just doesn't work.

    In the office, however, I was able to connect the MacBook to the 27 ′ iMac (2009) there without any problems.

    Do you have any idea??

    • Sir Apfelot says:

      Hello Ksenia!
      So it should actually work with the iMac in mid-2011. Could you try all the USB-C ports on the MacBook Pro? With Robert, who also commented here, surprisingly it worked on one port and not on another. Maybe that's the case with you too?

      • Ksenia says:

        I connected it to Thunderbolt. Both connections did not work. Do you think I should get a USB-C cable?
        Can it also have something to do with the operating system, for example that the operating systems are "too far apart"?

        • Sir Apfelot says:

          Hello Ksenia! Maybe I would try the USB-C Thunderbolt cable. Maybe that's the solution. The operating systems shouldn't be. It's clear that the 2011 iMac won't run Mojave ... and others will too. So it should be due to the wiring or something. Would be great if you report if it works with the other cable.

          • Ksenia says:

            I could install High Sierra on the iMac ...

            Unfortunately, I don't have a USB-C port ...

          • Sir Apfelot says:

            I might do a backup and then try High Sierra. But please make a backup beforehand ... not that anything goes wrong.

          • Ksenia says:

            It has now turned out - somewhat embarrassing - I had the wrong cable. An Apple Thunderbolt cable helped (it probably had a Mini Display Port cable before). I didn't realize there was a difference there. I also have to press cmd + F2 on myself.

            Thank you and greetings

          • Sir Apfelot says:

            Hello Ksenia! Thanks for the feedback. That’s also interesting to know. : D LG!

  14. Guido says:

    just to be on the safe side - or: before I throw myself into expense ...

    Hello Sir,
    I've looked and read a lot, but somehow I still couldn't find one thing: iMac 2011 as an extension (monitor) on the iMac 2019. The latter came today ...
    Every time I stumble upon the statement that 5K Mac's don't work as monitors. Wouldn't be the case with me…. But does "He" support this mode? In other words: can I connect my 2011 to my 2019?
    I just have to buy the TB2 / TB3 adapter and a TB2 cable.
    Thanks and best regards!

    • Sir Apfelot says:

      Hello Guido! I just discussed this with a colleague and he said it would work. The corresponding Apple support page calls the function "screen synchronization mode".

      But you need two parts for the connection:
      - TB3 to TB2 adapter (here at Amazon)
      - TB cable (TB2 connector) (here at Amazon)

      I linked the originals from Apple because I don't know if the third-party cables and adapters work properly here.

      • Guido says:

        Hello sir, supie, thank you very much!
        2 × 27 ″ looks mighty :-) Had thought for a long time about sense and nonsense, but throw it away, or sell for almost nothing ... I didn't care either. Then better invest a hunnie.
        LG Guido

    • Guido says:

      Everything great. Works without problems.
      19er connected to the adapter - since the 9er "only" has TB3. TB2 cable on and "plugged" into the 11th. Pressed wildly on the keyboard ... Tadaaaaa!
      Even if they have the same name or are labeled - there is, the small difference between "left and right of the space bar". ;-)
      What can I say ? It's brilliant. Once a huge display area and then the option to reactivate "the old one" via a key combination if necessary.
      So no wrong decision.
      Thanks again for your help.
      VG Guido

  15. Jean Schneider says:

    Hello Sir,

    Which 27 "monitors are recommended as a second monitor for the 2019 27" iMac Pro?
    I have connected an old Dell U2410, which works, but "overexposed" strongly, not controllable via its menu. It worked with a Thunderbolt to HDMI connection.

    Best regards,

    • Sir Apfelot says:

      Hi Jean! I don't think there are any official recommendations from Apple. I've never known anyone who has an iMac Pro either. Therefore, I cannot report from my own experience ...

      Basically, however, the cable can also be problematic (I've read). There was the recommendation, this one USB-C to Displayport (4K @ 60Hz) cable from Choetech.

      One monitor recommendation that I also found was that EIZO EV2785-BK, because it has a high pixel density and thus comes close to the dipsplay of the 5K iMac or the iMac Pro.

      I hope I could help you a bit with that.

  16. Romy says:

    Hi Sir Apfelot, thanks for the helpful article and replies to the comments. Do you think I have a chance to use a 27 ″ iMac (2013) as a display when both TB connections (ex works) are without function? Thanks and best regards Romy

    • Sir Apfelot says:

      Hello Romy! Sorry for the late reply. I think if the connections don't work, the image transfer won't work either. But maybe you have a friend with a Mac that you can test it on?

      • Romy says:

        Hello Sir Apfelot, thank you very much. It doesn't work with screen transfer. But very good and satisfactory with AirServer. Great tool! Sincerely, Romy

  17. Katja says:

    I did that too. However, I have to re-register the iMac as a screen every time. That means after each use of the screensaver, press the keyboard commands cmd / f2 again. For me that also means changing the keyboard every time. Isn't that easier? So that the iMac always recognizes itself as a screen as long as the MacBook and iMac are connected?
    Thanks for helping!

    • Sir Apfelot says:

      Hello Katja! I don't know how to "turn it off", but you can relocate the keyboard with a Bluetooth keyboard that can connect to multiple devices. This would be, for example "K380" from Logitech. Perhaps that will help you resolve the matter more comfortably.

  18. Nora says:

    Dear Sir Apfelot,

    Thank you for the article first, I used it to connect my old mid-2011 iMac to my beautiful new MacBook Pro 2019 spaceship. And: I am completely enthusiastic.

    Unfortunately, the old Apple wireless keyboard cannot be connected to the MacBook if I had to use it to switch and the iMac is somehow still "on". Is there perhaps a way to disconnect the bluetooth keyboard from the iMac and use it for the laptop?

    Best regards and thanks: Nora

    • Sir Apfelot says:

      Hello Nora! I'm glad it worked out with the iMac. Disconnecting and re-pairing the Bluetooth keyboard is relatively easy. At the top right, on the side is a round button. Hold this down for a few seconds until the green LED on the top of the keyboard flashes. Now go to System Preferences> Bluetooth on the MacBook Pro and pair the keyboard there, which should now be visible. LG! Jens

      • Nora says:

        Oh wow, that was a wonderful demonstration effect: according to your description, I have always tried exactly that before, without success - but now the keyboard was gracious and has connected and I'm happy.
        Thank you for the confirmation! And the help. :)

        • Sir Apfelot says:

          Well fine! Everyone knows about the demonstration effect. I always feel the same when I ask others for help. : D

          • Nora says:

            Good morning Jens, unfortunately the trick only worked once. If I stop mirroring the MacBook to the iMac and then try to connect the keyboard, I also see exactly how the iMac snaps the connection before the MacBook can. ("Keyboard connected ...")
            Is it possible to prevent that and force the desired new connection? Asks and greets: Nora

          • Sir Apfelot says:

            Hello Nora! Yes, you would have to permanently kill the connection to the keyboard on the iMac. You can do this via System Settings> Bluetooth, then select the keyboard and delete with the cross on the right. Then the keyboard should only couple with the one on their Mac.

          • Nora says:

            Thank you very much for taking the time to help strangers online! Unfortunately, I can no longer trigger the desired synchronization when the keyboard is completely disconnected. Maybe I'll have to get some old wired device to do this. Best wishes! :)

          • Sir Apfelot says:

            Yes of course! If you don't feel like having two keyboards, you can use one that can connect to multiple devices. Then you can just switch. Options here would be, for example, the brand new Logitech ergo or the 4in1 keyboard from Inline.

      • Bernhard says:

        Good afternoon Sir Apfelot,

        Thank you very much in advance for your article, thanks to which even a technician like me now knows what it takes to use an old iMac as a monitor. Before I buy an old iMac (mid 2011) to use as a monitor for my MacBook Pro (2018), I wanted to ask one more question about the keyboards:

        As I understand it, I only need the iMac's keyboard to enter the key combination to activate screen synchronization. As soon as this synchronization has taken place, everything runs via the MacBook Pro and the second keyboard connected to it. Is this assumption correct?

        It would be my wish to use two keyboards, because the wireless Magic Keyboard (2017) - which I have been using so far for input on my MacBook Pro and would like to continue using it for screen synchronization - according to the Apple website, does not work with an iMac ( mid 2011) is compatible.

        I hope to have asked my question in an understandable way and thank you for your help.

        Greetings from Switzerland,

        • Sir Apfelot says:

          Hello Bernhard! Yes that's right. You only need the keyboard for booting and for the key combination. Then you can decouple them, put them away or do something else. However, you will have to press the keyboard shortcut every time you restart your iMac. As an alternative to two keyboards, you could also use a Bluetooth keyboard that can be paired with several devices. I think this should work.

  19. michael says:

    i have an imac late 2013 and an asus zenbook (both computers have win 10). I would like to use the imac as a screen, but after a long search I didn't find any results which cable to choose for the connection. imac has thunderbolt 1 and laptop usb c. is it possible to use a normal cable usb c to display mini ( to use. Thunderbold should be backwards compatible?
    Thanks in advance.
    best regards

    • Sir Apfelot says:

      Hi Michael! This is not going to work. This connection to the iMac is not a simple cable like a monitor. The function is regulated by macOS and that would have to agree with your Asus Zenbook with Windows that it displays a monitor image. Apple certainly didn't implement that as it isn't even supported by all Macs. So: I don't see any chance there.

      • michael says:

        Many thanks for your response. Is there no possibility at all, not even by means of other cables, adapters, possibly even programs?

        • Sir Apfelot says:

          Hi Michael! I don't know of any solution. But that doesn't mean there isn't one. : D Maybe another reader has an idea ...

  20. Linda says:

    Hi all,

    I have an iMac 24 inch at the beginning of 2009 and now want to use the iMac screen as a monitor for my MacBook Pro Late 2016.

    I connected the two devices with a Thunderbolt (on the iMac) and HDMI via a multiport adapter (on the MacBook).

    When I click on monitors on the iMac, no other screen is recognized.
    Even clicking the option key and then clicking on "Detect monitors" did not help.

    The key combinations: cmd + F2 OR cmd + fn + F2 didn't work either.

    Can someone help me? What am I doing wrong?
    LG Linda

    • Sir Apfelot says:

      Hello Linda! There was never a 24-inch iMac model. I suppose that was a mistake, but your model is just probably not one of the ones that supports the feature. LG

      • Linda says:

        but it's actually a 24-inch iMac. That's what it says under "About This Mac". Well, then I'll have to live with the fact that this iMac doesn't support the function. Thank you for answering anyway.
        Lg Linda

        • Sir Apfelot says:

          Hello Linda! Yes, the ad doesn't lie and I've learned something again: there are 24-inch iMacs. : D But 24 inch models are definitely in the list of supported devices. For that reason it will unfortunately not work ... :(

  21. Keliki says:

    Great article. First of all, thank you for that!

    I have the problem that I connected my 27 “iMac from 2012 to the 27“ iMac from 2019 with the - Thunderbolt cable and the corresponding adapter on TB3.

    When I boot up both computers and then press my 2012 cmd + F2, the display goes completely black. However, I see that he takes over the screen from the 2019. However, I can't get the brightness. Does anyone have a tip for me?

    • Sir Apfelot says:

      Hello Keliki! Unfortunately, I have no idea what that could be and how to increase the brightness. But maybe another reader has a tip?

    • Daniel Meier says:

      Hello Sir Apfelot
      I have a late 2012 27 “iMac and would like to use it as a large monitor for my Windows computer with HDMi or VGA connection (thanks to Corona and home office).
      As you know, my iMac has two Thunderbolt 2 ports.
      On my first attempt using the MiniDisplayPort and HDMi adapter, my iMac made no attempt to detect any external device.
      Is there a Thunderbolt 2 to HDMi or Thunderbolt 2 to VGA adapter or do you have to take a different route?
      I look forward to your feedback

      • Sir Apfelot says:

        Hello Keliki! Unfortunately, there is only bad news. It's not a question of the cable, but of the software or hardware support of the iMac. There are few models out there that can use another Mac as an input signal, but I'm pretty sure Apple and Microsoft haven't talked about how to use an iMac as an external monitor for a Windows computer when it doesn't even work with every Mac goes. So unfortunately you won't find a solution there. But take a look here in the blog post I wrote something about cheap second monitors.

  22. Bernd Hebebrand says:

    Good day,
    I use an iMac 21 ″ privately (mid 2011) with which I am super satisfied (i7 and 16 GM RAM really okay for my needs)
    In terms of work, I have to use a Win-PC / Notebook and now I have to use the iMac as a screen for my Win-Notebook in the home office for reasons of space.
    A connection via mini display port did not work ... what can I do?

    VG Bernd

    • Sir Apfelot says:

      Hello Bernd! Unfortunately there is no way. Windows and Mac don't collapse like this. The two operating systems have to coordinate this and unfortunately Windows and macOS do not do that with regard to this coupling.

  23. Erol says:

    Good day everybody,

    Since the coronavirus, I have had my Imac 27 model at home at the end of 2015 so that I can work from home.
    I have the same model as a private home, how can I use two Imacs as a second monitor. Can someone help me there, please

    • Sir Apfelot says:

      Hello Erol! I don't know what to say. You posted your question right in the post that explains how to do it. If this doesn't work for you, you may not have the iMac models that support this feature.

  24. Rainer says:

    Hello Jens, Thank you very much for the detailed information about the screen synchronization mode. I've been using the mode for a long time with a MacBook Pro and iMac 27 "(Late 2013). What I'm missing: I would like to use the iMac's built-in camera for video conferencing. The MacBook Pro or Skype & Co. only recognize the integrated camera on the MacBook Pro, but not that of the iMac. Is there any way I can use the iMac camera when the screen sync mode is on?

    • Sir Apfelot says:

      Hello Rainer! The screen synchronization mode is unfortunately not something that Apple has actively pursued. For this reason, it only works with old iMacs. I searched but couldn't find a way to use the internal camera of the "external" iMac as a webcam. The data is simply not sent back over the connection cable. :-(

      • Rainer says:

        Hello Jens, thanks for the quick answer! Then all that remains is to clamp an external camera on the iMac and connect it to the MacBook Pro ... ;-)

  25. Tobias says:

    I would like to use my 21,5 ″ iMac late2012 with El Capitan as a second display for my MacBook Pro (Retina 13 inch, early 2015) with Sierra. According to the list, this should support you the TDM. I tried to connect it with an Apple Thunderbold cable. When I press cmtd-F2 it does not happen, only a short error signal tone sounds. Why is it that this is not working? Greetings Tobias

    • Sir Apfelot says:

      Hello, tobias! To be honest, I'm overwhelmed by that. Your iMac model should be able to. Would be interesting why he makes the error tone.

      • Tobias says:

        Whew, I still managed it. The trick was the keyboard.
        I had first connected an old Apple cable keyboard to the iMac (the white one with the plexiglass run on the outside) because my original wireless keyboard was broken. Then I bought the original Apple keyboard. And lo and behold! It works!

        • Sir Apfelot says:

          Yes, I still have this USB keyboard with the transparent plexiglass here. It has the nice nickname "crumb tray" because everything gathers so nicely in it. : D Great that it works for you now.

      • Tobias says:

        Hello again,
        do you think that with the help of the Blackmagic Ultrastudio Mini Recorder you can connect a Win PC via HDMI? In any case, the output is Thundebold 3.
        Greetings Tobias

        • Sir Apfelot says:

          Hello, tobias! I think it won't work with the Dock or Windows. It's an Apple-specific thing and has nothing to do with the normal Thunderbolt 3. Even with Max (see other comment) it didn't work out, despite using a TB3 dock and another Mac.

        • leveler says:

          The BlackMagic material is actually at home in the prosumer / professional sector, that is to say it is for people who more or less earn their money with video.
          The answer is "yes", you get the video output of a Win computer on a Mac with the recorder. But there you need a corresponding program to see what is coming from the Win computer at all. And then the whole thing has a feeling of a virtual machine.

          • Sir Apfelot says:

            Yes, you may get a picture here with gadgets, but that certainly has nothing to do with the connection that two Macs make. I strongly assume that the latency alone with the Win-to-Mac solutions with the Black Magic part would be significantly higher.

          • leveler says:

            You're right, it has absolutely nothing to do with connecting two Macs.

            The BlackMagic parts are really fast and have maybe 3-5 frames of delay. But in the end they are just boxes to get video content into a computer with a Thunderbolt connection (e.g. for any streaming stories). He could also buy a USB video grabber / capture card.

          • Sir Apfelot says:

            Then maybe I'd rather add another euro and buy an external monitor right away. : D

  26. Michael says:

    Hi, thanks for the great report, but it's not working for me. I have an iMac 27 mid 2011 and a MacBook Pro 2018. I bought the cable I use from Amazon. The term "CABLEDECONN USB-C Type c to Mini DisplayPort / Mini DP 4K 60Hz Resolution Active Cable Adapter 6FT with Aluminum Case Compatible with New MacBook Pro 2017 Samsung Galaxy S8 A0303"

  27. Alexandra says:

    Hello, thanks for the good explanation. I have a MacBook Pro (mid 2012) and would like to use my iMac 27 ″ (mid 2010) as a screen. There is a "Thunderbolt to Mini-DisplayPort" cable. Or do I need an adapter?
    Thanks for the help. LG

    • Sir Apfelot says:

      Hello Alexandra! I looked for such a cable but found nothing. For this reason, I would also recommend the solution with the Thunderbolt 2 cable and the adapter. That should actually work.

      • Alexandra says:

        Hello and thanks for the quick reply. So then I need these two cables from your comment on April 28.4th: ​​Apple Thunderbolt 3 (USB-C) to Thunderbolt 2 adapter and another Apple Thunderbolt 2 cable.
        Sorry, I just can't make out connections ... LG

        • Sir Apfelot says:

          Hello Alexandra! Sorry for my - unfortunately wrong - answer. Your old MacBook Pro doesn't have a USB-C. The iMac from mid-2010 didn't have Thunderbolt yet. For that reason, a perfectly normal Mini Displayport cable (without any adapters) would have to do the job. Here that from CableMatters for example, should go. If you have tried it, I would be happy to hear from you as to whether it worked. But should actually ...

          • Alexandra says:


            I still wanted to report back. The original question was: I have a MacBook Pro (mid-2012) and would like to use my iMac 27 ″ (mid-2010) as a screen. I have bought this cable from Gravis.

            It worked immediately, when plugged in, the iMac became the "monitor" of the MacBook, without any further shortcuts etc.
            Thanks again for the help.

          • Sir Apfelot says:

            Hello Alexandra! Thanks for the feedback. That's good to know. I didn't think a simple mini DP cable would work. But it may be that you have the "advantage" of not needing an adapter with your constellation. Your iMac and MacBook Pro share the same port. This is not the case with many others. They usually have a USB-C on one side and a mini DP port on the other.

  28. Catja says:

    Sir Apfelot, thank you very much for this great article!
    I've read through all of this, but I'm a little confused now and ask for help too!

    iMac (27-inch, late 2009)
    as an external monitor for
    MacBook Pro (13-inch, 2016, Two Thunderbolt 3 ports)

    Electric wire:
    MacBook +> USB C to HDMI / USB / USB Type-C Hub Adapter +> HDMI cable +> Mini DisplayPort Adapter to HDMI => iMac

    The wiring mentioned above does not lead to success….
    What should i replace? What do I have to buy new?

    Thank you!

    • Sir Apfelot says:

      Hello Catja! Unfortunately, I'm speaking here without any practical experience, as I don't use an iMac from the year, but I think the main problem is that the USB C HUB physically "rebuilds" the connectors, but the signal doesn't get through. You would have to Apple Thunderbolt 3 to Thunderbolt 2 adapter and Apple Thunderbolt 2 cable to get. I think it should work with that. If you give it a try, it would be great if you let me know whether it worked. Then I know that my recommendations are not nonsense. : D

      • Catja says:

        Bought cable but it doesn't work. Command + F2 / command + fn + f2 doesn't want to.
        The keys F1 / F2 etc. used as standard function keys, tried the whole thing with: both computers switched on and logged in, MacBook logged in - iMac not logged in to the user, restart the startup volume in hard disk mode but command + f2 doesn't want to either.

        Cables are new and from Apple, connectors work ... what could be the problem? what else can I try?

        • Sir Apfelot says:

          Hello Catja! Is your iMac in the list of supported models? That would be the first thing I would tap. Otherwise you can't really go wrong. :(

          • Catja says:

            hmmm, should, is an iMac 27-inch, late 2009 ... :(

          • Sir Apfelot says:

            Yes, it should actually be compatible. Unfortunately, I have no more idea what it could be. The Apple cables are 100% compatible, but maybe another reader has a tip on what to test?

          • Robert says:

            At that time, one of the Thunderbolt ports on my MacBook Pro was defective, that fooled me. But that was TB-2, so it can happen sooner (metal tab was in the way).

            Then a very stupid question: you pressed the buttons on the iMac, right?

          • Catja says:

            I have now found out that iMac Late 2009 does not have Thunderbolt, now I have to try Mini DisplayPort, there is for example
            LMP USB-C 3.1 to Mini-Displayport cable
            an idea whether such a direct cable - without an additional adapter, could work?

          • Sir Apfelot says:

            Hello Catja! With these cables, I honestly don't know for sure whether it will work. One reader has had a good experience with a mini DP cable (it says somewhere in the comments), but a direct USB-C to mini DP cable has (as far as I know) nowhere worked. The variant that is a bit more expensive, but probably has the highest compatibility, is the Apple TB 3 to TB 2 adapter and then that Apple TB 2 cable.

          • Catja says:

            Now it finally worked, my iMac switches over automatically :) :)

            iMac (27-inch, late 2009) + MacBook Pro (13-inch, 2016, Two Thunderbolt 3 ports), cable:

            LMP USB-C adapter Mini-DisplayPort
            LMP Mini-DisplayPort Cable Mini-DisplayPort

  29. Drilon says:

    I have an imac 2011 27 inch model that I want to use as a second monitor for my surface book 2. what kind of connections do i need?

    • Sir Apfelot says:

      Hello Drilon! I can't give you 100% information because I haven't tried it, but the connection sometimes fails when you connect two Macs via a Thunderbolt 3 hub because the "monitor Mac" does not recognize that another Mac is sending something . 99% of Windows devices are definitely not getting the right signal. I'll leave the 1% over because I haven't tried it myself, but as far as I know, this connection is purely an Apple thing.

  30. Leon says:

    Thank you for the great and detailed article. I even have a question now. I have a MacBook Pro (13-inch, 2018, four thunderbould 3 ports) and an iMac (Retina 4K, 21.5-inch, end of 2015) that I would like to use as the second display on the Macbook. It is now not clear to me whether this works, at apple on the website it is stated under by the end of 2 2015 inches that no longer works. but what about the 27 incher? I would appreciate a quick reply
    Greetings and stay healthy

    • Sir Apfelot says:

      Thank you for your question and your praise.
      Unfortunately, no 2015 iMac works. No matter what size. It's only the older Macs that still have this mode built in. Sorry :-(

      • Leon1 says:

        Wow thank you, the answer was really quick.
        Oh dear. that would be one of the practical things for the home office
        do you know an alternative solution? the i mac is unfortunately very slow and so no longer useful for me. I work in the design sector, I work a lot with Adobe programs and 3d software. he just doesn't take part anymore. I already reset it, but unfortunately that doesn't really help.
        Would like to have access to the bigger screen but use the more busy and processor of my Macbook.
        Greetings and thanks again for your quick reply

        • Sir Apfelot says:

          Hello Leon! Unfortunately, there is no alternative to using the iMac as a monitor. But you can pimp the iMac with an external SSD quite cheaply. I had already recommended this to a reader recently, who thanked me overjoyed for the tip because the Mac now feels like a new computer. You can do this with an external SSD such as this one from SanDisk use and then via Carbon Copy Cloner or Super Duper copy everything to the SSD. Then select the SSD in the system extensions> Startup disk and restart the Mac. The first restart could still be slow, but the second restart at the latest should be quick. And working with the iMac should feel good too.

          • Leon says:

            That sounds great is ordered directly. Thank you for the great tips. I'm really excited about your side, really strong. I'll get back to you when I've tried it and report ^^

          • Sir Apfelot says:

            That pleases me! If you have any problems with cloning, just report it. The SSD is presumably pre-formatted in ExFAT. You would have to change this to the format of your startup disk before copying. If you're using Mojave or Catalina, it's APFS, otherwise it's case-sensitive Mac OS Journaled. But as I said: just report if something is stuck somewhere.

  31. Uli says:

    have iMac (21,5 inches, mid 2011) with High Sierra 10.13.6 and want to use it as an external monitor for an Elitebook 850.
    Got it with one
    USB-C to DisplayPort tried:

    And a DisplayPort to mini DisplayPort
    But it didn't work with any cable. The cmd-F2 is not noticeable in any way.

    What is wrong there?

    Many greetings Uli

    • Sir Apfelot says:

      Hello Uli! The problem is: The Elitebook is not an Apple computer. It only works on Macs ... not between PC and iMac.

      • Uli says:

        Many Thanks. There is no clear statement on the web, for example
        [Link removed from sir]
        For me it also makes sense if there are cables for it.

        Greeting Uli

        • Sir Apfelot says:

          Hello Uli! I have now looked through various forums again and there are always people who say you have to install this and that card on your PC to make it work. The people who do it then write across the board that it didn't work out. For this reason I stick to my statement: iMac as an external monitor for a Windows PC does not work with a cable or adapter. I also removed the link in your comment because it explains how it supposedly works, but it just doesn't work - this is shown by the reports from people who have tried it and ask in forums what it is now related to.

  32. Uli says:

    Thanks for the detailed answer. I am impressed. Then I send the cable back

    • Sir Apfelot says:

      But of course. I like to be convinced otherwise if someone actually manages it in practice, but all forum posts that I've read show something else. : D So better save money and return cables.

      • Cellar says:

        Dear Sir Apfelot,
        - (I would have read earlier in your forum) -
        I can also confirm your statement: "iMac as an external monitor for a Windows PC does not work with a cable or adapter".
        Also NOT with the following setup:
        iMac 21.5 mid-2011 with Thunderbolt interface, PC mainboard with Thunderbolt header and plugged-in Thunderbolt 3 PCIe adapter card with connection for the PC graphics card (the PCIe adapter card provides the video signal from the graphics card for the TB3 interface to monitor monitors with TB3 Input), TB3 to TB2 adapter from Apple for connection to the iMac.
        DID NOT WORK!
        But maybe it's something like Fermat's last sentence: As long as the impossibility is not proven, there will be repeated attempts to see whether it might work after all. (Fermat's theorem was only proven after 300 years, so keep the thread open!)

        • Sir Apfelot says:

          Hello cave! Yes, there is something about Fermat's theorem. : D And thank you for contributing a few more variants that DO NOT work. : D

  33. Torsten says:


    First of all, thank you Sir Apfelot for this thread, great!

    Also at the risk of having missed something above, I ask for your help, as I may have gotten confused with the cables.

    I would like to use the iMac 27 ″ at the end of 2009 as a second monitor on my 2 2019 ″ as an extension.

    I tried the Apple Thunderbolt 3 to Thunderbolt 2 adapter, which is also linked at the top.

    Then I tried the Apple Thunderbolt Cable (also linked above), but unfortunately nothing works. Then I took the mini display port cable instead of the Thunderbolt cable, and no reaction either.

    Settings as described here several times: new iMac registered, old iMac 2009 in the login screen.

    Now asked really stupid ... the F2 key is brightness, isn't it? With that I only achieve an increase in brightness on the Apple keyboard (the "standard function keys" setting is deactivated), or do I just have the mega-board in front of my head in terms of keys?

    CMD + F2 only comes the nice error tone from the iMac 2009.

    Can you possibly help me?

    Thanks and Regards


    Then n

    • Sir Apfelot says:

      Hello Torsten! As far as the cables are concerned, everything should be correct. Because of the F2 key: You should have an "fn" key at the bottom left of your keyboard. You press it at the same time as the F2 key so that it does not change the brightness, but executes "F2". Does this work?

      • Torsten says:

        No, unfortunately the fn key also makes no difference, always just the monotonous error tone ????

        • Sir Apfelot says:

          Hello Torsten! This is strange ... your iMac should actually support the mode. Can you continue to update macOS on it? Unfortunately, I have no clue whether macOS is doing anything at all, but that would be my only tip as to why it could be.

        • Robert says:

          Just to be on the safe side: Command + Fn + F2 :)

  34. Torsten says:

    Hello Sir Apfelot, hello Robert,

    Thank you very much, no, unfortunately no solution either. Always just the monotonous error tone. Just checked for updates to be on the safe side, everything is up to date. High Sierra 10.13.6 on 27 ″ at the end of 2009 ... everything fits together with the Apple article on this subject.

    It's a shame ... because it should work ... and here in the thread there are really many options and it worked for many.

    Is there a system setting somewhere that can accidentally deactivate the function or something?

    Do you know anything like that?

    Thank you very much again!

  35. Torsten says:

    Hi all,

    the 3rd cable variant finally actually worked ????

    The solution was the direct MiniDisplayPort to USB-C cable. Just plug it in and the iMac Late 2009 switched over automatically.

    I didn't know THAT before ... that cables from external manufacturers work better than the original Apple adapters / cables.

    Here is the link to the corresponding cable that worked for me now:
    CableDeconn USB Type C to Displayport

    It works, wonderful! Now I first have to return various cables and adapters ????

    • Sir Apfelot says:

      Hello Torsten! Thanks for the link. I'll use it at the top of the article so that others don't have to search long. It's great that it works for you!

  36. chris says:

    Moin Sir Apfelot,

    I hope I haven't read anything above ...
    I would like to use my iMac 27 ″ in mid-2010 as a monitor for my wife's Windows computer, because I have a new iMAC and the old one can still be good for something.
    I bought a 3in1 mini display port to VGA HDMI DVI adapter from CSL.
    I have already tried it via HDMI and / or VGA with Command + F2 and / or Command - FN - F2 both in the login screen of the Mac and logged in.
    The MAC screen then jumps to a poorer resolution mode, but I can still see the Mac's desk there ... after a few seconds it jumps back to the higher resolution screen.

    Any idea?
    I'm a little desperate because it should actually work; (
    Is it possibly the cable?

    Thanks in advance and best regards

    • Sir Apfelot says:

      Hello Chris! Unfortunately, this mode, in which the Mac functions as an external monitor, does not work between Windows and Mac, but only between Macs. What happens to you is as follows: The Mac thinks that an external monitor is connected to the HDMI port on which it should display its image. Since this does not seem to support the high resolution of the iMac, it switches to a lower resolution and outputs its image via the mini DP port. So unfortunately that won't work for you - no matter which cable you use. The Mac hardware is here across the board.

  37. Jens says:

    Hello Sir Apfelot,

    I also have problems connecting my MacBook Air 2020 to my iMac 21,5 Late 2011.
    In the meantime I have tried all possible cable configurations suggested here. The most expensive Apple connection Thunderbolt 3 adapter and Thunderbolt cable does not work either. I'm so slow with my Latin at the end. Is it possible that the target display mode no longer works with macOS Catalina?


    • Sir Apfelot says:

      Hello, Jens! Unfortunately, I don't use Macs with it, but I do here Read in this thread that macOS Catalina was the solution for some people because there was a bug with the TDM under High Sierra. So actually it should work under macOS Catalina ... no idea what it depends on you. :-(

  38. Jens says:

    Hello Sir Apfelot,

    Thank you for your prompt reply. Unfortunately I cannot install Catalina on my iMac late 2011. It's really bad ... that it doesn't even work with Apple's own adapters.
    There has to be some solution?

  39. Jens says:

    As I just found out, it no longer works with catalina. Apple is annoying me extremely slowly, maybe I should turn around after 15 years of Apple.

    • Sir Apfelot says:

      Hello, Jens! The link you posted in the comment unfortunately resulted in a 404 error. Could you send it to me again? As far as I could read, it should still work under Catalina.

  40. Jens says:

    the link
    I went to an Apple dealer today and they confirmed that the Target Display Mode does not work with the MBAir2020. Probably wasn't the first to ask him this. Apple has a bug with the MBAir2020, I doubt whether this will be fixed.

    • Sir Apfelot says:

      Hello, Jens! Thank you for your hint. On the Apple side it is really clear: The target display mode no longer works with macOS Mojave and Catalina or even newer systems (such as Big Sur soon). That is actually a shame ... but it was also a little specialty that was only used by a small target group. Unfortunately, you are one of them. :-(

  41. Rudi says:

    Hello Sir Apfelot,
    A few weeks ago I bought a new MacBook Pro (13 ″ / macOS Catalina version 10.15.6) and now I want to use my old iMac (27 ″ / mid 2010 / OS X El Capitan version 10.11.6) as a screen. I bought a cable (USB-C to Mini Display Port), as has already been mentioned several times in various comments. When I plug in the cable and press the appropriate key combination, the iMac's screen goes black and stays black. Actually, all requirements that have been described should be met, but the connection does not seem to work. Do you have any idea what could be the cause? I've read through (most) of the comments, but haven't gotten any smarter.

    • Sir Apfelot says:

      It's actually a good sign that he's responding to the key combination. That means you probably only have one cable that isn't working. Maybe you will try again with another one linked here. Unfortunately, I don't have any more tips. : D

    • Jens says:

      It doesn't work with Catalina and the MacBook Pro / Air 2020. Apple has switched off the target display mode from Mojave, see my link above.
      I have the same problem and now have to buy an external monitor.

      • Sir Apfelot says:

        Thanks for the hint. I add Mojave to the article so that the other readers with Mojave or higher do not have any more hopes.

      • Robert says:

        Fortunately, this only applies to the hardware mentioned (Air 2020).
        Catalina on my MBP 13 ″ (Early 2015) still works well with my iMac, if I know anything else about Big Sur, I'll get in touch.

        • Sir Apfelot says:

          Hello Robert! Yes, then the Apple support entry probably means that the iMac that is used as a monitor must not run with Mojave. But thanks to the old hardware we have with the iMacs, that should seldom be the case. In a pinch you just have to install High Sierra on it again.

      • Robert says:

        Maybe I misunderstood you, but the limitations of the OS only apply to the iMac. If there is High Sierra running there, it’s no longer working since Mojave, right. As far as the MacBooks of 2020 are concerned, I can't check that on my "old" MBP 13 ″ 2015 as a source, even with Big Sur (beta) it still works.

  42. Melanie Bartel says:

    Hello Sir Apfelot,

    Today I took my new Mac Book Pro "15" from work to home office. At home I have an old iMac (21.5 inches, mid 2011). Now I was hoping that with "CABLEDECONN USB-C Type C to Mini DisplayPort / Mini DP" everything works ... but unfortunately nothing comes with cmd + F2 ... not even with cmd + F2 + FN ;-(

    Can that be due to the cable? What else could I try?


    • Sir Apfelot says:

      Hello Mel! We heard from another reader that it could also be due to the system running on the iMac that is supposed to act as the display. Do you happen to have Mojave or something newer on it? LG

  43. Melanie Bartel says:

    I have macOS High Sierra on my iMac. Do you think that's the problem?

    LG Mel

    • Sir Apfelot says:

      I think Target Display mode is still running under High Sierra. It only seems to have disappeared under Mojave. Then it can really only be due to the cable. But I can hardly make a recommendation here, because if I look at the comments of the other readers, then for some the one USB-C to mini-DP cable works for others, the solution with the Apple adapter and cable. But what will work for you is difficult to predict. :(

    • Jens says:

      Hi Mel,
      same constellation as mine. It no longer works with the new MacBooks. No matter what kind of system is installed.

  44. Melanie Bartel says:

    Hi Jens,

    does that mean it doesn't work at all? ;-( or should I order the Apple cable with adapter?
    Thunderbolt 2 cable from Apple (0,5 m or 2,0 m) &
    Thunderbolt 3 to Thunderbolt 2 adapter


    • Jens says:

      Hi Mel,
      even with the adapter 3/2 and Thunderbold cable it no longer works. I bought it specially. Now there are € 80 cable scrap lying around here. I've tried all the options on cables, it no longer works with the new MacBooks.
      A MacBook from 2009 with an adapter 3/2 and Thunderbold on the iMac 2011 works fine. I also tried the MiniDP on DVI (Original Apple) plus DVI on TB3. Everything does not work.
      I have now bought an Eizo monitor in order to be able to work properly at all.

  45. Sabine Omann says:

    Hello Jens,

    I have now read the entire course and see such creative and good approaches to the further use of not so up-to-date hardware. Therefore I dare to ask the following question:

    Connecting iMac and Windows works in this case?

    iMac beginning 2009 27 “with HP Envy Convertible 15

    Many say there is no chance but I don't like to take it completely;)

    Thank you for your feedback signal
    Sabine from Graz

    • Hello Sabine! So with a cable it doesn't work between Windows and iMac. The only way I could think of would be to use a remote desktop application like AnyDesk. So that you can control the PC remotely via the iMac and see its screen. But of course this is always associated with a slight delay in the display and the input of commands, which can interfere with everyday work. I would not recommend it ...

  46. Roland M. says:

    Hello, Jens!
    Thanks for your thread. This has already been helpful, but do I still have a question? I recently bought a completely new iMac 21 ″ (model A1418) Mac OS Catalina. However, I still have my old iMac (model mid 2011) Mac OS High Sierra, which I use as a second screen for my new iMac.
    The two iMacs are connected with Thunderbold.

    The key combination (cmd) + (F2) performed on the old iMac and my new iMac in use as the main screen. I performed the key combination on the old computer because it doesn't seem to work on my new iMac.

    Now to my problem:
    Everything works very well in operating mode. I'm using the keyboard from the old iMac on the new iMac.
    When I shut down my iMac, both screens close, but my old iMac goes back to operating mode and then I have to switch the keyboard again so that I can shut down the old iMac. This is very annoying because I only want to use my old iMac as a screen and no longer as a PC.

    Apparently the synchronization mode doesn't work either or I misunderstood something. Please provide specific help.

    Thanks for your feedback
    GlG Roland from Vienna

    • Jens Kleinholz says:

      Hello Roland! To prevent or make it easier to move around, you could use a keyboard like the Logitech craft that can be connected to up to three devices. I don't know of a solution via macOS now. LG

  47. Hi Jens,
    thank's for the Tipps!
    I had a working system consisting of MacBookPro from 2018 / macOS 10.14.5 and iMac late 2013 / macOS 10.10.5.
    Then I have the iMac on 10.14.5 as well. updated and now the monitor function no longer works, I had a long phone call with Apple Support, in the end they said it would go up to Mac OS 10.13 at most. High Sierra on the iMac. Unfortunately it still doesn't work.
    Do you have experience with this problem or do you know up to which OS it could work?
    (I don't want to use PS 10.15 yet because important software is then no longer available)
    Thank you very much
    Greetings from Munich, Marian

    • Jens Kleinholz says:

      Hello Marian! I think it should actually work out easily with macOS 10.10.5. Could you have recently updated the MacBook Pro when it suddenly stopped working?

      • Marian says:

        Exactly, I upgraded from working 10.10.5 to 10.13, which according to Apple should still work

        • Jens Kleinholz says:

          Ah ok! That could have been it. But unfortunately I have no idea up to which OS should work. Maybe you still have a backup of 10.10.5 so that everything works out again for the time being? Then you could try an update to 10.11 and see whether the iMac still works as a monitor.

  48. Markus says:

    Moin Apfelot, Community,
    I'm currently looking sore on the Internet and can't come to a clear statement. Can I connect my Macbook 2020 to the iMac 2013?
    Then with 2 cables. So Thunderbolt 3 to 2 adapter and then the Thunderbolt 2 cable?
    I think I read on the Apple Support website that the path no longer works for the 2020 model.
    Does anyone have the same setup and can you report from experience?
    VG, Markon1

  49. Sascha Bähr says:

    At the moment we have the problem that our iMac (27 inch 2012) no longer wants to start and we would still like to save the data.
    The report sounds really very good ????
    As I read it out, the second car has to show the login screen, which ours unfortunately no longer does.

    Do you also have a tip? We still have a 27 inch from 2010 and it works.

    Thanks and greetings from Hamburg

    • Jens Kleinholz says:

      Hey Sascha! If the Mac does not start anymore, using the iMac as a monitor will not help you, as it will still prevent you from accessing the data. So you would either have to try to boot with another hard drive or remove the hard drive. Greetings from Northern Hesse!

  50. Ralf Schraven says:

    Hi all,
    I don't know if the question has been asked here before. I have an iMac 27 ″ (late 2015) and a MacBook Air (2013). I would like to pair these two devices and use the MacBook Air display as a second display. What options do I have here? I first connected both of them with a Thunderbolt 2 cable. When pressing the key combination cmd + F2 or cmd + fn + F2 nothing happens. I have also read that this function is supported on iMac's younger than late 2014. Do I have other options for using the MacBook Air display as a second display for the iMac?

    I would be very happy to receive answers.

    • Jens Kleinholz says:

      Hello Ralf! Unfortunately it doesn't work in the "direction". The iMac can only be the display. Unfortunately, a MacBook Air can only "send" but not "receive". Unfortunately, I don't have any good news. There was once a hardware solution that could be used to connect two Macs, but unfortunately I can't remember the name. :( Was kind of a radio connection between one Mac and the other. As a result, unfortunately, a bit delayed ... but maybe still bearable.

  51. Andreas Mogg says:

    Hello Sir Apfelot,
    don't want to start all over again as this topic has been described several times but I'm already pretty confused and desperate what should work now and what shouldn't? Subject iMac as a display: There are as many reports on the net as it is easy (only not for me !!) I want to use my iMac (Mid 2011-21,5 ″ - Sierra) as a display for my new MBPro (2020 - Catalina). Original TB 3 to 2 adapter bought, original TB cable bought, tried all key combinations and previous tips: Nothing works! - The cmd + F2 key has no function! Can only play the MBPro screen on the iMac via screen sharing but not as an additional display and in a botch view. (Also goes in the other direction, by the way). What is actually about "BootCamp does not work for this function"? I am using Windows through BootCamp. I realize that it doesn't work with Windows. It's everywhere. But what does that mean? There must be no Windows on the computer which is installed via Boot Camp, or not Windows in use? I only want to use the screen for Mac OS! Would it work if Windows is only on the computer via Parallels? Am I correct in assuming that a maximum of High Sierra may be on the old iMac and not BOTH Macs? Pretty annoying the subject. According to Apple everything is very easy and now I have to pay idiot tax (approx. € 100.-) for the adapter and cable that you don't otherwise need.

    • Jens Kleinholz says:

      Hi Andreas! Unfortunately, the user reports are very, very different. There are also readers who can use the iMac as a display with a 2020 MacBook Pro. But don't ask me what's the catch. Unfortunately, I don't have a Mac available and I can't test it. I can't really imagine that it's up to you to boot camp. Bootcamp is actually like a separate partition and shouldn't affect the macOS system - but I'm not 100% sure here. I've always avoided boot camps. : D

      Maybe another reader has a tip on how to solve the matter with your MacBook Pro from 2020. The iMac shouldn't be the problem according to the compatibility list.

  52. Robert says:

    If you are interested: a new MacBook Air (Apple Silicon) from 2020 goes well with my iMac 27 “Late 2009 with High Sierra, the display target mode kicks off.
    That's what I call sustainability, the iMac runs better after 11 years than on the first day, ok, thanks to SSD ;-)

  53. Walter Stefan Fuchs says:

    Point 1: THANK YOU very much for the great efforts to offer such a support page
    Point 2: I just can't see the forest for the trees now. I have a Mac mini 2018 (MRTR2D / A). I want to use my iMac 27 “Late 2009 as a monitor. Which cable do I need now?

    Can I use hard drives attached to the iMac with the Mac mini? thanks

    • Jens Kleinholz says:

      Hello Walter Stefan! With pleasure. : D And to 2. What connections does your Mac Mini have? Even the flat USB-C sockets? That would be important to say which cable you need. The iMac Late 2009 should definitely have a mini-DP port on it, if I'm not mistaken.

    • Walter Stefan Fuchs says:

      Thanks ... ..Mac Mini has 4x Thunderbolt 3, so USB-C.

      If I'm actually only using the iMac as a monitor ..... can I somehow use the internal iMac hard drives when using the Mac mini as the main computer?

      • Jens Kleinholz says:

        Hello Walter! Unfortunately, no. This is actually just a connection for video. The iMac remains a stand-alone Mac that wants its hard drives to itself. ;-)

  54. Christian says:

    Hello Sir Apfelot,
    I hope you can also help me if necessary. I beamed my iMac 21,5 ″ (end of 2013) back to High Sierra and wired it to my newly arrived M3 Mac Mini (Big Sur) with the original Thunderbolt 2 adapter and TB1 cable. Unfortunately, none of the key combinations mentioned in the login window give access to the "old Mac". The combination cmd + fn + f2 results in only one system tone.
    Do you happen to have any idea / solution?

    • Jens Kleinholz says:

      Hello Christian! You can shut down both devices again. Then boot the Mac Mini and log in and then boot up the iMac and log in. And then try cmd + fn + f2 again. I think you have to be logged in to do this and sometimes it matters in which order you start the devices. The iMac should be the last.

    • Bernhard says:

      Hi Christian
      have the same problem. Has that worked now?
      I'm grateful for every tip.

  55. Pierre says:

    Hello Sir Apfelot
    I have an iMac 27 ″ late 2012 and a Macbook Air 2013 and cannot use the iMac as a screen. I connected both devices with tunderbolt cables and all F2 + cmd or FN key combinations do not work. Both devices shut down again and tried again that doesn't work either. Does anyone have an idea or solution?

    • Jens Kleinholz says:

      Hello Pierre! As a tip I read somewhere that you should not start the iMac until the MacBook Air has started up. Maybe you will try again. Otherwise the cable should be the right one. I don't see what it could be related to.

  56. Benjamin says:

    Hello. I read your article with excitement. With which cables is it possible to connect a Windows laptop (usb-c and hdmi) from an iMac end of 2013 (Mini DisplayPort large) to use the iMac as a monitor? Thanks for the help

    • Jens Kleinholz says:

      Hello Benjamin! Unfortunately there is no cable for this. Unfortunately, you cannot pair the iMac with a Windows computer to use it as a monitor. This only works with selected Apple computers. I'm sorry. :(

  57. Bernhard says:

    many thanks for the comments! I have now played through the whole thing in every possible way ... .. unfortunately without success :( Could it be that Big Sur and the new M1 are the problem? I have a 27 Mac from mid-2010 with High Sierra 10.13.6. Should but somehow fit. Thank you very much for your support.

    • Jens Kleinholz says:

      Hello Bernhard! Another reader had recently contacted Apple Support and they told him that Macs from 2020 (still with Intel processors) should not work either. However, there was other feedback from readers who still managed it. I can hardly tell what is right now. But I think Apple won't have a focus on it and will sooner or later remove the feature from the system. Or they have already deleted it. What should work, however, is the solution with Air Display, which I briefly mentioned in the article above.

  58. Bernhard says:

    Hello Jens Many thanks for the prompt reply. I don't think Apple supports the cause either. You mean airplay? I've already tried. Unfortunately, I have the problem that Airplay is not visible in the menu bar for me. I tried to activate it several times via System / Library / CoreServices / Menu Extras and Displays menus. This only leads to a short twitch in the menu bar and then disappears again… .what the hell. In iTunes, however, I can stream via Airplay. I then also reinstalled High Sierra. Didn't help either ... you might see a solution in the "crystal ball" Thank you for your support!

    • Jens Kleinholz says:

      Hello Bernhard! I meant "Air Display". This is not Airplay, but an app that can integrate an iPad or another Mac as an additional monitor. You can here read more about it and install the software.

  59. MC says:

    I have an iMac late 2013 with OSX 10.11.6 on it. Now I wanted to connect my new Macbook 2020 Intel to this iMac, but all I get is this Apple sound that comes when something goes wrong.
    I connected the two with a Thunderbolt 3 to Thunderbolt 2 adapter and here it continues with a Thunderbolt 2 cable to the iMac.

    I've tried registered and also in the log-in window, with the fn key and without, with the original Apple keyboard and others, but nothing works.

    Does anyone know why this doesn't work?

    Many thanks for your help.

    • Jens Kleinholz says:

      Hello MC! You could try again first booting up your MacBook and then booting up the iMac. Sometimes that helps. Otherwise, you could try another cable. There are users who have reported to me that the Apple cables and adapters did not work. I don't know why that is, but that was the feedback I got.

      • MC says:

        I just got the following answer in another forum:

        The iMac at the end of 2013 has a Thunderbolt 1 (A) port, which is why a Thunderbolt 2 connection is not possible.

        Have you ever heard of that? Is that actually a MiniDisplay Port even though it has the Thunderbolt symbol next to the slot?

        • Jens Kleinholz says:

          Hello MC! This is new to me that it could be because of it. It may be that they have different TB versions, but actually everything should be backwards compatible. And from what I've heard from a reader, it doesn't even have to be Thunderbolt. The reader had a mini-DP cable and a Thunderbolt to mini-DP adapter. No Thunderbolt protocol will go over it and still it works for him ...

  60. Horst Andresen says:

    Question about connecting two Macs and many time-consuming attempts:
    Can someone tell me which cables (possibly plus adapters) I have to order in order to be able to use two iMacs together as monitors.
    Mac 1 is main device: runs on Sierra 10.12.6, 27 ″, end of 2013.
    Mac 2 as a second monitor, Sierra, 10.13.6, 21,5 ″, late 2009.
    The attempt via Thunderbolt 2 and keyboard commands cmd and FS 2 failed. An installation via Firewire hard disk mode instead of a startup disk.
    I'm so slowly at the end of my Latin ...
    It would be great if someone had the right tip. Through the whole search I came across this page until today I can say: great page with a lot of news. As a solo entertainer you are usually left out.
    Sound Health!
    Horst Andresen

    • Jens Kleinholz says:

      Hello Horst! Unfortunately, you won't be able to do it with any cable in the world, because your iMac is 21,5 inches and it is the 27 inch model from 2009 that can be used as a monitor. Here's the problem ... not with the cable. :(

  61. Okay, thank you very much for your answer. I also have a 27 ″ from mid-2007, El Capitain, 10.11.6/XNUMX/XNUMX.

    Is that too old? Or what do you mean?

    Thank you for your help.

    • Jens Kleinholz says:

      Hello Horst! At the top of the article are the models that are compatible with the mode:

      iMac end of 2009 27 "
      iMac mid 2010 27 "
      iMac mid-2011 to mid-2014

      ... unfortunately yours from 2007 falls out ...

  62. Wolli says:


    Despite reading the posts, I still don't understand which cable or adapter to use. I have a 21,5 "iMac late 2013. It has two Thunderbolt interfaces on the back. What I can't find out is whether it's thunderbolt 1 or 2. I'll get a Mac mini M1 soon. This of course has a USB-C interface. Whether Gen1 .1 / 2 or Gen2 .1, I don't know. Anyway, I want to connect the Mini to the iMac and use it exclusively as a monitor. Do I now need a USB Gen1 .1 or USB-C Gen2 cable. 1 etc. on thunderbolt 1, or thunderbolt 2? I am very happy about every constructive answer. I'm just older.

    • Jens Kleinholz says:

      Hello! I know it's complicated and unfortunately not always the same, otherwise I would have just recommended a cable and that's it. But there is the strange case that some cables work with one and not with the next. However, I received this recommendation from my reader Robert, which I also have somewhere above in the article: JSAUX USB C to Mini DisplayPort adapter and DeLock cable Mini DisplayPort. Maybe you will try it with that?

    • Philipp Stumpp says:

      Hello Wolli! I hope you get this message here, because I am currently facing an (almost) similar problem. I have an iMac late 2013, but the 27 ″ model and I also want to buy the new MacMini with the M1 chip. Have you been able to successfully pair your iMac and if so, which cables did you use?

      Best regards,

  63. Karol Kruger says:

    I am now on the verge of despair or I misunderstood the article.
    I use an iMac Retina 5K, 27-inch, 2017 (Thunderbolt 3) to work and would like to connect my iMac 21,5, at the end of 2013 (Thunderbolt 2). I connected both devices with an original Thunderbolt 2 cable and a Thunderbolt adapter to Thunderbolt 2. The older iMac has Mac OS 10.15.7 as the current version and is in the login mask. for my user. Or may there be no user account on this iMac at all? I just can't get a connection as a second monitor, can someone help me

    • Jens Kleinholz says:

      Hello Karol! I don't think the iMac should run anything newer than macOS High Sierra. That was the statement from an Apple support representative. If you want to reinstall an old macOS on the iMac, you have to reboot it and hold down CMD + ALT + R immediately after the restart. Then the macOS with which it was delivered will be installed. And THAT it should actually work. : D

  64. Caro says:

    Hello Jens, Your site is worth its weight in gold ;-) Unfortunately, I don't understand a lot about the whole technology and can't quite keep up with the discussions. May I therefore ask you whether and how I can combine the following combination ?:
    iMac (21,5 ″, late 2013) with Catalina 10.15.7 - MacBook Air (M1, 2020) with Big Sur 11.1
    Do I have to set the iMac's operating system to High Sierra 10.12. "downgrade"? Which cables / adapters should I try? Thank you very much, Caro

    • Jens Kleinholz says:

      Hello Caro! Yes, I think you need to downgrade the iMac to High Sierra. And when it comes to cables, I would recommend the combination that my reader Robert has successfully used. You can find the two products here in the section "Update 12.12.2020/XNUMX/XNUMX: Mini-DP to USB-C solution". Good luck with it!

      • Caro says:

        Thank you very much for your tip. Unfortunately it didn't work for me. So again for the community:
        iMac late 2013, 21,5 "with High Sierra 10.13.6 and Mac Book Air 13" (M1,2020) with Big Sur 11.1 worked for me with the following adapters and cables despite different booting, taking into account the login window and pressing the cmd + Fn + F2 and cmd + F2- key combination NOT working:

        1.Apple Thunderbolt 2 cable (2,0 m)
        Thunderbolt 3 to Thunderbolt 2 adapter

        2. USB-C to mini DisplayPort cable
        CABLEDECONN USB-C Type C to Mini DisplayPort / Mini DP

        3. DeLock cable Mini DisplayPort St / St
        JSAUX USB C to Mini DisplayPort adapter

        Nevertheless, thank you very much for this great forum, keep your fingers crossed for the others that it works with their devices!

        • Markus says:

          Hello Caro, have you found a solution in the meantime? I have exactly the same setting and the same problem.
          LG Markus

  65. Jörg says:

    Hi Jens,

    Your site is really worth gold (has already helped me with a few problems). However, I now have a presumably imminent problem and would like to ask whether there is already experience on this.

    My previous constellation was: 1x iMac 2012 21,5 ″ with macOS 10.15.7 and 1x iMac 2013 21,5 ″ with macOS 10.15.7. I connected the two directly via a Thunderbolt cable (both iMacs still have the Thunderbolt 1 ports).

    Now my 2012 iMac has died a hardware death and this week I'll get a Mac mini 2018 as a replacement, which has Thunderbolt 3 ports and will probably also have macOS 11 (Big Sur) installed.

    My question: can I still use the 2013 iMac with the Thunderbolt 1 connection cable and a TB3-to-TB2 adapter that I still have as a second display in screen synchronization mode for the Mac mini? Or do I need a different adapter or even a different cable? (Or is it not possible at all?)


    • Jens Kleinholz says:

      Hello Jörg! Yes, that could work with the adapter and the TB cable. But I think you need to downgrade the iMac to macOS High Sierra. To do this, boot the iMac and hold down Shift + Option + Command + R (⇧ + ⌥ + ⌘ + R). Then it starts in the Internet Recovery and installs the system with which the iMac was delivered. That should be something older, but the mode for "use iMac as display" should already work. Please report if that worked.

  66. Alex says:

    Hello and thank you for the extensive contribution.
    I have a MacBook Pro (13 inch, 2020, four Thunderbolt 3 ports) with Catalina 10.15.7 and Intel Iris Plus Graphics 1536 MB graphics card.

    The 27 ″ iMac from the end of 2012 also runs the same Catalina version and has the NVIDIA GeForce GTX 660M 512MB.

    With a USB-C cable, starting from the MacBook, to Thunderbolt - no success.

    Even with a USB-C to HDMI cable - into an HDMI to Thunderbolt adapter - no success.

    Is there now only the € 80 option for the two Apple adapters?

    • Jens Kleinholz says:

      Hello Alex! I think the problem could be that the iMac is only allowed to run under High Sierra at the most. When that is done, the expensive Apple adapters should also work. At least that's what other readers who spoke to Apple Support told me.

  67. Andreas Mogg says:

    Update on my request already made at the beginning of December 2020:

    Imac Mid 2011 (Sierra - meanwhile High Sierra) should act as a display for my MB Pro 2020 (Catalina).
    Despite frequent attempts with the original cable TB - TB and original adapter TB 3 (USB-C) to TB 2 no success until today.
    So much for the past.

    Now my update on my latest experiences (It's getting stranger and stranger)

    I recently bought a second-hand Apple Thunderbolt Display 27. (Because I think it's optically very nice in contrast to today's displays)

    As a display with the original adapter TB 3 (USB-C) to TB 2, the Thunderbolt Display 27 works perfectly as an external screen for my MB Pro 2020. That means that the video signal comes into the display.

    Now came my plan to outsmart the system:

    With a direct connection from TB Display 27 to Imac Mid 2011 (daisy chain and therefore without an adapter from display to Imac), I wanted to use the Imac Mid 2011 as a screen, as originally planned.

    Result - also unfortunately no!
    The video signal continues to go from the MB Pro 2020 to the Thunderbolt Display 27, but unfortunately not to the I Mac Mid 2011.

    But now comes the big a-ha experience.
    Had my daughter's I Mac (End 2012) with me for a few days. I tried the same constellation.
    I Mac End 2012 (with Catalina !! - as main computer) via TB - connection to Thunderbolt Display.27 and then via TB (Daisy Chain) to I Mac Mid 2011.

    See there - works perfectly! Immediately I was able to arrange all three screens!
    In BOTH directions!
    Even if I use the older I Mac Mid 2011 as the main computer and then go to the I Mac End 27 via the TB display 2012, I can use it as a screen, even though Catalina is already running on it. (It is always said that max.High Sierra is suitable for the screen function)

    The following result and question at the same time result for me from this test arrangement:

    It can only be due to the video signal of the MB Pro 2020 or the adapter TB 3 to TB 2!

    Otherwise, why is the video signal from the MB Pro 2020 only transmitted to the Thunderbolt Display 27 and then "stuck" there, but the video signal from the I Mac at the end of 2012 was passed on from the Thunderbolt Display 27 via daisy chain to the I Mac Mid 2011?

    In any case, I'm at the end of my game! - But maybe there is someone in the forum who has an explanation for it.

    Anyway, thanks and LG.

    • Jens Kleinholz says:

      Hi Andreas! The problem with this is that it's not just a normal video signal as I understand it. The MBP sends a "you are now a display" signal to the iMac and that will probably not go through the Thunderbolt display. If you were to connect a normal monitor, a video signal would certainly also arrive there.

      • Andreas says:

        Hi Jens,

        sorry, I'm probably standing next to the shoes, but your explanatory assumption is unfortunately incomprehensible to me.
        You mean that the "You are now a display" signal gets stuck in the Thunderbolt display.
        Why can I "loop" it through the Thunderbolt display when I connect my daughter's I Mac (late 2012)?
        In your opinion, what difference would there be if I would connect a second Thunderbolt display via daisy chain instead of my I Mac in mid-2011? Does that work then? With the current LG displays that have Apple approval (with Thunderbolt 3 connection), it should work in any case.
        LG Andreas

        • Jens Kleinholz says:

          Hi Andreas! I am not a technology freak and I am not familiar with this special information transfer that Apple uses here for the "iMac is display" mode. I only understood it to mean that when the iMac is connected in series behind the Thunderbolt display, it no longer shows an image. And the only reason I can think of for this is that this particular signal is "stuck" in the TB display. A second TB-DIsplay would work in my opinion.

  68. Philipp Stumpp says:

    Hello Jens, I greet you!

    I've been following this post for days because I'm about to buy a new MacMini 2020 and use my iMac (Late 2013) as a monitor. Now I came up with a strange idea, but since I'm not an expert I am probably completely wrong. But …

    ... wouldn't it also be possible to connect the iMac to the HDMI 2.0 input of the new MacMini using a MiniDisplay cable and an HDMI adapter (optionally also a MiniDisplay cable - HDMI)?

    • Jens Kleinholz says:

      Hello Phillip! So in terms of the connectors it will probably work, but unfortunately I can't say whether the right signal will come across. You'd have to try that. There are so many imponderables with this iMac-as-monitor thing that I cannot make a definitive statement about it. But, if you try it, I would be very interested in the result! The iMac then has to run on High Sierra or lower.

      • Philipp Stumpp says:

        Greetings Jens and thanks for your quick answer! As soon as my MacMini arrives, I will of course report to the Apple community. Since I'm already doing research, I have another question about the MiniDisplay port. For the adapter you suggest above (JSAUX USB C to Mini DisplayPort Adapter), the description on Amazon says: "Please note that this C to Mini DP adapter is NOT compatible with monitors or devices with a Thunderbolt 2 connection." Now I'm confused again.

        1) Does that mean that I definitely have to use a MiniDisplayPort CABLE or

        2) that this adapter actually ONLY works with products that also have an original MiniDisplayPort? (My iMac has Thunderbolt 1)

        3) Thunderbolt 1 uses the same connector as MiniDisplayPort or not? Doesn't it matter if I use a MiniDisplayPort cable or a Thunderbolt (1 or 2) cable?

        Has anyone here already paired a Thunderbolt 1 iMac with the new MacMini? I read all the comments again. It's a mess, but the cables from Apple are so expensive * aaaaarrgh *

        Kind regards and Jens, you are doing a great job here, keep it up!

        • Jens Kleinholz says:

          Hello Phillip! Yes, Apple cables are extremely expensive and unfortunately not necessarily the best choice in this case. I've already had readers where the Apple cable + Apple adapter didn't work, but the JSAUX adapter did. But to your questions: 1. I don't think you can use a simple cable because the signal for the target display mode is "more" than just the pure video signal. But unfortunately I'm only reading the crystal ball here. 2. The JSAUX adapter is USB C and comes in a USB-C port, which is Thunderbolt 3 (as far as I know). But maybe there are also devices with TB 2 in the form of USB C. It should work there too. 3. You have to test that. In this case I would rather try a Thunderbolt cable, as more is transmitted here than with a mini DP cable.

          I know there are many "maybe" and "actually" in this matter. Unfortunately, this is the case with this connection ... I keep getting very different responses and cannot see any real pattern. With the JSAUX adapter, however, I received the message that it works with a current Mac.

  69. Michael Scherer says:

    Hi all,

    Since I didn't want to throw my iMac 27 ″ in the bin in 2010, the topic was of course very interesting for me. Therefore, I would like to give you a brief feedback on what works for me:

    Mac Mini Late 2018 I5

    Monitor 1:
    Imac 27 "2010 over JSAUX USB C to Mini DisplayPort adapter and Delock Cable DisplayPort mini male / male in target display mode

    Monitor 2:
    Philips 272B8QJEB / 00 68,58 cm (27 inch) monitor via HDMI

    Both in the resolution 2560 x 1440, I'm super happy with the solution, the iMac now serves as a monitor and hard drive (in the network).

    Maybe it will help some, greetings and, despite the current situation, nice Easter days.


    • Jens Kleinholz says:

      Hi Michael! Thanks for your report. I'm sure this will help some readers choose. I have also linked your product names directly - I hope for the right products. LG, Jens

  70. Lisa says:

    Hi Jens,

    I have an old iMac early 2008 that was put on Linux Mint.

    Could I connect my Windows 10 laptop to it and use the iMac 08 as a screen?

    I saw that it was not listed in the "prerequisites", I just wondered if it might be worth a try and inquired about your assessment.

    Best regards,

  71. Jim says:

    Hi all,

    I have a follow-up question about the update from 18.03.2021/XNUMX/XNUMX, with which you, as a layperson, might be able to kindly help me.

    I would like to use my iMac (end of 2009 27 inch) as an external monitor for my Lenovo Thinkpad X1 Yoga. Since the Lenovo laptop is my work computer, only a connection via a connection cable (and no network transmission or similar) is possible.
    In the update of March 18.03.2021, XNUMX you write that a transfer should be possible in principle, according to the procedure you described.
    Unfortunately nothing happens when I connect a mini-dp (iMac) / Thunderbolt C (Lenovo) and click cmd + F2.
    Does anyone have any idea why this might be? I have also tried other "cable combinations", such as mini-dp to HDMI or VGA, to no avail.
    Is there possibly a matter of attitude, for example with the resolution

    I would be very grateful for any tips!


    • Jens Kleinholz says:

      Hello jim Unfortunately, I am overwhelmed with Windows PCs because I don't know which ports are transmitting what. What system is installed on your iMac? A maximum of macOS High Sierra can run here.

      • Jim says:

        Hi Jens,

        I have OS X El Captain installed. In my understanding, that should be the operating system before Sierra and thus also High Sierra, so that it won't be the show stopper here?

        My Windows computer has a Thunderbolt C connection, so the basic technical requirements should be met, which in turn means that the transmission should work. So it would only be a matter of attitude, right?


        • Jens Kleinholz says:

          In theory you are right about the statements, but the problem is that there is not much to adjust. :(
          But it shouldn't be due to macOS. I can't say anything about the Windows computer ...

  72. Robert says:

    Hi Jens,
    I found your instructions here over a year ago and at the time I established a super stable connection between my old iMac and my MacBook Air, which enabled me to use the old iMac as a monitor. Now I've bought a new MacBook Pro (2017), which of course only has USB-3 ports. So I bought an adapter for my old Thunderburd cable so that I can continue to use the construction. So far so well that worked for almost a month. But now there is a problem: My iMac suddenly no longer wants to recognize the MacBook. Switching off, restarting, reconnecting the cable, etc. all does not work. If you wait a few days (!), The first connection works again, but after a break the old problem comes back. The cables are totally functional and also originals from Apple. Maybe you have an idea what else I could do? But renew the cable again? I also looked for a USB-3 to Thunderbird cable to connect directly without an adapter, but I couldn't find that anywhere ... Thanks for all the ideas!

    • Jens Kleinholz says:

      Hello Robert! Hmmm ... that sounds strange. How could a break have such an effect ??? I can't explain it to myself technically at all. As a test, you could again create a new user and start from this and try to see whether a connection is established. Or did you maybe change something in the time when it stopped working? New software installed or something? The iMac should still have a maximum of High Sierra.
      Otherwise you could try the other cable-adapter combination again, which also works with some: JSAUX USB C to Mini DisplayPort adapter and Delock Cable DisplayPort mini male / male. Maybe it works with that? Otherwise I'll really run out of ideas ... :(

  73. Rui says:


    I've read so much that I don't even know what I need. ;-))

    Maybe one of you can help me, would be very grateful.

    My setup:

    Macbook Pro 13 ′ at the beginning of 2011 is to be connected to an Imac at the end of 2012.

    Is that possible and if so, which cable do I need. ;-))

    Thank you

  74. Nina says:

    Hi Jens,

    I was so excited when I read your post !! My old iMac still has uses. So I immediately ordered cables and adapters from Amazon. Today it arrives and the result is unfortunately ... nothing happens !!

    Here with setup:

    MacBook Pro 13 ″ M1 2020
    iMac 27 ″ in mid-2011

    Cable Delock cable Mini DisplayPort M / M black but only 1 meter long
    Adapter JSAUX USB C to Mini DisplayPort adapter

    I had macOS 10.13 (High Sierra) on the iMac. After 2 keyboards (Apple Keyboard Bluetooth and Apple Keyboard with cable) did not work with this macOS, I reset the iMac to its original macOS, so it is now macOS 10.7.5 (Lion) on the iMac. And yet it doesn't work.

    It's not the problem with the MacBook Pro with the M1 chip or Big Sur?!?!

    I hope you can help!

    Greetings from Hamburg

    • Jens Kleinholz says:

      Hello Nina! Yes, unfortunately you cannot predict the result. I have no other reader who recommended the cable and adapter to me because that is exactly what they do. I'm sorry it didn't work out for you. If I remember correctly, he has a Mac Mini M1. So actually Big Sur and M1 may not be the problem. I'm starting to get the feeling that it is pure coincidence whether it works with a combination of devices or not. I know, unfortunately that doesn't help you now, but I can't say any more ...: /

  75. bm says:

    thanks for the great article!
    I have a question, too:
    I want to use an iMac (late 2012) as an external monitor for a new iMac (with Thunderbolt3). Is that possible and which is the right cable?
    Thanks in advance

  76. Leonie says:

    Dear Jens, thank you very much for your great article!

    Since the last time I just ordered some kind of cable and unfortunately it didn't work, I prefer to ask again this time:
    I would like one
    - MacBook Air (Retina, 13-inch, 2020) with macOS Big Sur with one
    - iMac (27 ″, end of 2013) with macOS Catalina
    . connect
    I would then install macOS High Sierra on the iMac.
    Could you help me which cables to buy?

    Thank you for your help!!

  77. Ole says:

    Hi Jens,
    The problem is also for me - on the one hand iMac 27 ″ late 2009 with High Sierra and on the other hand my MacBook Pro from 2016 with Big Sur and the question can both devices be connected? On the Apple support page ( says: “The other Mac you want to connect to must be from 2019 or earlier. In addition, macOS Catalina or older should be installed on it. “Are there any experiences with this whether a connection is also possible under Big Sur? LG Ole

    • Jens Kleinholz says:

      Hello Ole! Unfortunately, I don't have any experience to offer, but I've heard from other readers that Apple Support even says something about macOS High Sierra at most. I think Big Sur falls flat with it when they point it out. But maybe someone else has an experience report ready.

      • Small says:

        I was able to realize the following connections. My iMac is from 2011 (macOS High Sierra). I can use a MBP 13 ″ from 2012 with MacOS Catalina via Thunderbolt. A 2014 MBA with BigSur was also recognized. The iMac reliably fulfilled the function of the second screen.

        Sincerely, Mic

  78. Small says:

    Maybe I skipped it, I'm interested in whether it will still work with the new M1 MacBooks? So for example iMac from 2011 and new MB-Air with M1?

    Sincerely, Mic

    • Jens Kleinholz says:

      Hello Mic! Unfortunately, I cannot make a binding statement on this. But I think that a reader with the Mac Mini M1 wrote to me that it still works for him.

  79. Timo says:

    Moin moin Jens, first of all I would like to thank you for the great article! I also like other of your articles very much and cannot be found anywhere else.

    I have an iMac from mid-2011 and would like to use it as a monitor for a Windows PC with an HDMI output; In other words, HDMI (male) to Thunderbolt (female / better: male, since an additional Thunderbolt cable is very expensive). Unfortunately, I only ever find variants to Mini Displayport:
    FOINNEX Hdmi to Mini DisplayPort Adapter, Gold-Plated 1080P Active HDMI to Mini dp Video Converter Male to Female for Apple Cinema Display (24/27/30 inch), iMac 2009/2010, Dell MDP Monitor, Projector

    Can you or the community help me? I think it would be a shame to give the iMac away ...

    Kind regards

  80. Bachmann Anna says:

    Hi Jens,
    Thank you for such an informative article. I also have a question about the connecting cables. I would like to connect my iMac 27 to a new MacBook Pro with M2011 in mid-1 and use the iMac as a monitor.
    -What kind of connection cable do I need then?
    -And is it still possible to use the iMac despite a defective hard drive? However, it continues to work via an external hard drive with High Sierra.


    • Jens Kleinholz says:

      Hello Anna! Yes, you can also use the iMac if you boot it from an external hard drive. It doesn't matter - the main thing is that it is still running. I can't say for sure whether the thing with the M1 MBP works. One reader said he could still do it, but a few others wrote that it didn't work. Ultimately, you'll have to test it out. With your constellation, you need the two products that I see under the paragraph "Update 12.12.2020/XNUMX/XNUMX: Mini-DP to USB-C solution". I would be super happy if you could give me feedback as to whether it works for you. A few empirical values ​​would help the article here - and certainly many other readers too. Thanks to you!

      • Bachmann Anna says:

        Hi Jens,
        Thank you very much for your quick response. I don't want to give up the hope that it will work with M1 :) Of course I will report whether it works for me, I just need time :)

        Thanks again

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