All good Macs must come to an end, and one day, unless you hoard them away, go to someone else. That someone else could be a close relative, a purchaser, or the fate of recycling. The last thing that you want to do is simply shut down one day and send your Mac away, even if it is just for scrapping. This article explains what you need to do to prepare a Mac which is running Catalina before parting with it. If yours is still running an older version of macOS, then you should find this article more helpful.
If your Mac has multiple user accounts, you’ll need to repeat account-specific items for each of the user accounts for which they are relevant: that applies particularly to iTunes accounts, iCloud, and Messages.
Backup (twice)
Before going any further, ensure that you have a full backup, and preferably another complete copy of your internal storage. When you’ve made your farewells to the Mac that has seen you through the last few years, run one last backup to Time Machine, then turn Time Machine off.
I like then to make a full clone of the boot volume using Carbon Copy Cloner or SuperDuper. If in the next few weeks I discover that something important is missing from my new Mac, I can then go straight to that clone and rescue it. I still have the option of accessing its Time Machine backups too.
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