Updating software

Back up your data, check your applications for compatibility, and depending on which iMac model you have, download High Sierra or Catalina.

(182788)

Depends on the computer.

Backup your data regardless.

This guide tells you what you can upgrade to depending on your machine's age*:

http://www.macmaps.com/docs/DOC-13695/

*Links to my pages may give me compensation.