You’ll also want to read “ OS X: About Disk Utility‘s erase free space feature.” A note at the end starts to get to the heart of the matter. However, that Apple article skips over the nuance of completely erasing an SSD. “ What to do before you sell or give away your Mac.” Item #6 in that document launches the discussion and links to a pretty good article: “ How to reinstall macOS.” That article, by the way, has a nifty table that summarizes which versions of macOS you can install from the recovery partition. The first thing to do is read Apple support article. You’ll want to securely erase that SSD, but it’s a bit tricker than a plain hard disk. These days, because SSDs have been an option for Macs for almost a decade, it’s very likely that you have, or will soon have, a Mac for sale that boots from an SSD.

Securely erasing a hard disk isn’t hard to do, and it’s been discussed in many places. Back when I did that last, the Mac had a hard disk. It’s been awhile since I sold an old Mac.

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