software update on Browser Safari
have older MacOS high sierra
need to do software update on browser Safari
iMac 21.5″, macOS 10.13
Question marked as
Assuming you have the macOS 10.13 version listed in your Tag Line, the most up to date version of Safari it can run is Safari 13.1.2. It be updated to a newer Safari version than that.
If you have a different version of macOS, the check your Software Update section in the Apple Menu, or the App Store App for potential updates to Safari.