Wondering which versions of macOS or Mac OS X your Mac can run? Our macOS compatibility checker will show you what Macs the different versions of macOS and Mac OS X support so you can tell what macOS you should be running on your Mac.
What Mac operating systems can my Mac run?
Apple releases a new version of the Mac operating system almost every year – but the new version of the Mac operating system will not support every Mac. Each year more and more Macs fall by the wayside, unable to be updated to take advantage of the latest features.
Read more at Macworld.com