Upgrade From Catalina?
I have a 2013 Mac running Catalina. Can I upgrade any further on my IOS?
iMac Line (2012 and Later)
Question marked as
Macs run macOS and iOS is for iPhones. If your 2013 Mac is an iMac, then it cannot upgrade beyond Catalina. If it is a Late 2013 MacBook Pro, mid-2013 MacBook Air, or Late-2013 Mac Pro, then it can upgrade to Big Sur.
See macOS Big Sur is compatible with these computers - Apple Support