upgrading from High Seirra
how to upgrade from High Sierra OS
iMac Line (2012 and Later)
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Back up your data, check your applications for compatibility, and depending on which iMac model you have, click on Mojave, Catalina, Big Sur, or Monterey. If you get a Mac App Store preview page, change the https at the beginning of its address to macappstore.
Catalina and newer won't run 32-bit software; download and use Go64 to scan for it. To look up other programs, click here.
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