Upgrading to a new Mac?
To protect your privacy when you sell or give away your old one, first erase your personal information and files. Even if you trust the person receiving your old Mac, there’s the risk of a later malware infection recovering your personal details.
Fortunately before you sell checklists are readily available:
- Apple suggest these steps: Backup, Signout, Erase, and reinstall MacOS in What to do before you sell, give away, or trade in your Mac
- The authoritative site, iMore echoes the above, but with screenshots and more detail, in How to reset your Mac before selling it