Which macOS is installed?
1. From the Apple menu () in the upper-left corner of your screen
2. Choose About This Mac.
The window that opens might look different from the example shown here, but it always includes the macOS name followed by its version number. If you need to know the build number as well, click the version number to see it.
This example shows About This Mac on a MacBook Pro with macOS Ventura 13.0: