Why You Probably Can't Use Your Old iMac As a Display

Can you use an old iMac as a display for a new Mac or extra display for a MacBook? Let's take a look.

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Now I'm often asked this question. Can you use an old iMac as a display for say a new Mac Mini that you've just bought or maybe a second display for a MacBook Air or MacBook Pro? The answer, I'll just tell you right off, is probably not. Let me explain why. 

So first if you recall there being a feature like this, there was and it will still work under certain circumstances. This feature is called Target Display Mode. You can read about it here at this Apple Support Page. It even shows a nice picture of a MacBook and an iMac and about how one can be used as a display for the other. But if you look further you're going to find immediately that there are two problems. 

First, the iMac that you're trying to use as a display needs to have been produced between 2009 and 2014. So pretty old iMac models. Then, on top of that, they have to be running macOS High Sierra or earlier. This was only supported up to that version of macOS. So if you're past that it won't support it at all. Now even if your Mac does fit as one of those it still is not going to work if your newer Mac is newer than 2019. That Mac has to have an older version of macOS. It has to have macOS Catalina or earlier. Certainly Macs from 2019 can run versions all the way up to, and including, macOS Ventura. So, you have to stick with an older version of macOS on your new Mac and on your old Mac you have to have an older version of macOC. So that really narrows it down to only a few configurations that would actually work. Furthermore, you probably don't want to restrict yourself to using macOS Catalina or earlier just so that you can use your old iMac as a display. 

Now there is something you should know about those iMacs from 2009 to 2014.  I'm assuming that you're only thinking of the 27" iMacs for this. A 27" iMac might make a nice display. However, the screens on those iMacs were before Apple introduced retina displays. So those screens were actually 2560 by 1440 and the screens after it were double the width and double the height. So four times the number of pixels. Those newer iMacs have brilliant displays and are much higher quality than these old iMacs. In fact, if you just wanted to get a display that is 2560 by 1440 you can easily find one now. As a matter of fact they are higher quality, lighter weight, and use less power. They usually run somewhere between $100 and $200. But I often try to discourage people from trying to use 1440 screens with their newer Macs anyway because using it at full resolution the interface elements, like the Menu Bar and Buttons and such, are too small and using it as a  retina display makes everything way too large. 

So now that you found out that you probably can't use your old iMac as a display I would recommend getting a 4K Screen, at least. Not a 1440 one for a new external display. 

Now there is something else that you can do. You can use AirPlay. So AirPlay is the way that you can send audio or video from an Apple device to something else, like say a TV for instance. It does it wirelessly and it works really well. Starting a couple of years ago Mac's support AirPlay. So you can actually AirPlay from a device, like an iPhone, to a Mac and then see your iPhone screen on your Mac. You can also AirPlay from Mac to Mac. So technically you could have a newer Mac and then use the older Mac as an AirPlay device. Thus, wirelessly extending your screen to the second display. 

The problem with that is the Mac has to be pretty new to do that. You can see a list here of all of the different Macs that support it and you could see that it has got to be a 2019 or later iMac or maybe the 2017 iMac Pro in order to do that. But two problems with this. One is you're going to have a much slower connection. Now if you're just looking at spreadsheets, maybe that is fine. But for doing anything where you actually need to screen quickly, and I don't mean just playing games or watching video, it could just be editing photos or working with apps with lots of interface elements, AirPlay may not be ideal. Plus, if you've got an iMac that can support this chances are you could resell it right now for much more than what it would cost to get yourself a nice 4K display that you can plug directly into your newer Mac. So while AirPlay can be useful to use here and there I wouldn't use it as a regular solution for having a second display. 

Instead I would spend $300 or so to get a 4K display and resell that Mac to recoup the costs. I probably should also mention you could do screen sharing as well. But that is difficult to setup. You have to use the old Mac to connect to the newer Mac and setup Screen Sharing and you really can't set that up as a secondary display. It's going to be mirroring the first display and it is going to be even slower than AirPlay and probably isn't going to produce good results. It might be nice as a temporary solution or to occasionally use your old iMac screen, keyboard, mouse or trackpad to connect to, say, another Mac like a Mac Mini that you've got. But I wouldn't use it as something you would work with everyday. 

So while it seems like a great idea to use an old iMac as a display for a new Mac, it really doesn't workout well. Either practically or economically to do so. Hope you found this useful. Thanks for watching.