Upgrade

Back up your data, check your applications for compatibility, and depending on which MacBook model you have, click on High Sierra, Mojave, or Catalina. Unless you have a specific reason to run an older OS or your computer can't be upgraded past it, get Mojave if you depend on 32-bit software and Catalina otherwise.

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Use Time Machine or set up a bootable clone, and click on those words above.

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