About This Mac shows the version and build of your Mac operating system.
Is your Mac operating system up to date? Does it meet the system requirements of an app or device that you want to use with your Mac? Which macOS versions are earlier or later than the version you're using? To help answer these questions, you need to know which macOS version you're using now.
Check About This Mac
From the Apple () menu in the corner of your screen, choose About This Mac. The version of your operating system appears beneath “macOS” or “OS X” in the window that opens. To see the build, click the version. This example shows macOS High Sierra version 10.13, build 17A365:
The following tables show the version and build of each Mac operating system made available from the Mac App Store,* starting with the most recent. If you're not using the latest compatible version, learn how to update the software on your Mac.