upgrading mac high sierra 10.13.6 on older mac, late 2013
How do I upgrade my mac High Sierra 10.13.6 Older Mac - late 2013s
iMac 21.5″, macOS 10.13
Back up your data, check the application compatibility table, click here, and then on the download link for a more-recent OS. That iMac model's maximum one is Catalina.
Catalina and higher won't run 32-bit software; if you upgrade to one of them, use Go64 as well.
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