I have a IMAC from 2013 and need to install Mac Os Big Sur - why can't I do that?
I have a IMAC from 2013 and need to install Mac Os Big Sur - why can't I do that?
iMac 21.5″, macOS 10.15
Because Catalina is the last compatible macOS. See the following from Identify your iMac model - Apple Support
iMac (21.5-inch, Late 2013)
Model Identifier: iMac14,1
Part Number: ME086xx/A, ME087xx/A
Latest compatible operating system: macOS Catalina 10.15.7