Can I really not use my mid 2010 27" iMac as an external monitor for my new 2018 Macbook Pro 15"???

Question

Can I really not use my mid 2010 27" iMac as an external monitor for my new 2018 Macbook Pro 15"???

I have a mid 2010 27” iMac that I have been using as an external monitor for my mid 2013 Macbook Pro 15” via a Thunderbolt 2 cable. Works famously. Just bought a new 2018 Macbook Pro 15”, purchased the Thunderbolt 3 to 2 adapter, plugged it in and nothing. The new Macbook does not recognize the external device. Apple has given me varying explanations but nothing substantive. After exhaustive trouble shooting there is no issue with ports, software, cables or adapters. It seems so strange to me that my 27” monitor won't work with a current Macbook? Is this really a thing? Is there a work around? Any help would be greatly appreciated. Alternatively I am looking for a replacement external monitor should there prove no solution to this. Looking at LG 34WK95C-W and BenQ EX3501R as possible targets. Thoughts there would also be appreciated. Thanks y'all.

MacBook Pro 15”, macOS 10.15

Posted on Apr 23, 2020 12:21 PM

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Answer 1

Apr 27, 2020 11:47 AM in response to Malcolm J. Rayfield

@Malcolm J. Rayfield, THANK YOU!!! I was using the correct Mini-DisplayPort cable, I had just purchased the wrong adapter not realizing there is a difference between Thurnderbolt 2 and Mini-DisplayPort as they use the same port. Somehow Apple does not know this is a thing so there are a bazillion people out there buying new monitors because they don't think their 27" iMac will work with new MacBooks. Yikes. Thank you Malcolm.

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Answer 2

Apr 23, 2020 4:38 PM in response to Speedracerjvb

It will still work, but not with a Thunderbolt adapter.

Use your iMac as a display with target display mode - Apple Support

Target Disply Mode uses Mini DisplayPort for the 27" 2009 and 2010 iMacs, and Thunderbolt for 2011-2014 iMacs.

To get Mini DisplayPort from a Thunderbolt 3/USB-C port on your MacBook Pro you need a USB-C to Mini DisplayPort cable or adapter, such as:

https://www.startech.com/AV/display-and-video-adapters/usb-c-video-adapters/usb-c-mini-displayport-cable~CDP2MDPMM6B

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Answer 3

Apr 24, 2020 7:01 PM in response to Speedracerjvb

Are you sure the cable you were using is Thunderbolt (lightning bolt icon on the plugs)? The 2019 iMac uses Mini DisplayPort, and shouldn't work with a Thunderbolt cable, even though the plug will fit.

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