Which macOS is good for my Late 2015 iMac?

I'm currently on macOS Sierra 10.12.6 and I would like to upgrade to a newer OS. But which one would be better for these specs?


iMac (Retina 5K, 27", Late 2015)

Processor 4 Ghz Intel Core i7

Memory 8 GB 1867 Mhz DDR3

Graphics AMD Radeon R9 M390 2048 MB


Thank you


iMac 27″, macOS 10.12

Posted on Nov 16, 2023 2:28 AM

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Posted on Nov 16, 2023 8:08 AM

8GB RAM is adequate, but 16-24GB would be better. I'm running Monterey flawlessly on 20GB (2018 Mac mini) but so far haven't ever actually needed more than 16GB.


Three OS versions you should consider:

a) Mojave (10.14) - Last version with 32-bit app support. If you are still on Sierra you might have legacy applications that are still important... or not.

b) Big Sur (11) - I usually consider the penultimate supported OS to provide optimal performance.

c) Monterey (12) - Slightly more resource intensive than Big Sur which can be noticeable on older hardware (16GB+ RAM recommended), but it is also the oldest that supports Apple iWork (Pages, Numbers, etc) updates so installing this will offer better modern software support.


Big Sur and Monterey also prefer to run on SSDs. If you have a 1TB Fusion drive and wish to run Big Sur or newer I would suggest buying a high capacity external USB 3.0 SSD and installing MacOS onto that.

10 replies
Question marked as Top-ranking reply

Nov 16, 2023 8:08 AM in response to mihaigagiu

8GB RAM is adequate, but 16-24GB would be better. I'm running Monterey flawlessly on 20GB (2018 Mac mini) but so far haven't ever actually needed more than 16GB.


Three OS versions you should consider:

a) Mojave (10.14) - Last version with 32-bit app support. If you are still on Sierra you might have legacy applications that are still important... or not.

b) Big Sur (11) - I usually consider the penultimate supported OS to provide optimal performance.

c) Monterey (12) - Slightly more resource intensive than Big Sur which can be noticeable on older hardware (16GB+ RAM recommended), but it is also the oldest that supports Apple iWork (Pages, Numbers, etc) updates so installing this will offer better modern software support.


Big Sur and Monterey also prefer to run on SSDs. If you have a 1TB Fusion drive and wish to run Big Sur or newer I would suggest buying a high capacity external USB 3.0 SSD and installing MacOS onto that.

Nov 16, 2023 8:34 AM in response to padams35

padams35 wrote:

Supported as in the OS supports the hardware, not supported as in still receiving Apple updates.
(Although Big Sur did just receive a security update last September)

Personally, I wouldn't recommend a version of macOS that is no longer supported. Not to mention that there are current versions of software that require supported versions of macOS.


I guess I did mention it. 😎

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Which macOS is good for my Late 2015 iMac?

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