If you are selling your MacBook or Mac, trading it in, or just passing it on to friends or family – you would be wise to wipe the Mac and restore it to factory settings first. This is partly so that your data stays safe, but it will also avoid any issues at a later date that could come about if you don’t disconnect that Mac from various services and software you might use. It also means the new user can restart the Mac as if it was brand new.
Just remember that if someone is going to be using the Mac after you, removing personal information alone isn’t enough – you also need to make sure there’s a working version of macOS installed afterwards. Read our guide to selling a Mac.
Another reason why you might want to wipe your Mac is to perform a clean install of macOS – which can be a good way to fix issues with your Mac if it’s starting to behave oddly or you are worried you might have a virus. Wiping a faulty Mac will allow you to set it up like a new Mac – which will hopefully fix any software-related issues you are having.
Read more at Macworld.com