How can I erase my hard drive and be sure that there is no hidden files or anything that can compromise my personal security?
[Re-Titled by Moderator]
Original Title: Selling my iMac
iMac (2017 – 2020)
Follow the directions at > What to do before you sell, give away, trade in, or recycle your Mac - Apple Support
Follow the directions at > What to do before you sell, give away, trade in, or recycle your Mac - Apple Support
What to do before you sell, give away, trade in, or recycle your Mac - Apple Support is all you need to do.
For magnetic media the longer answer is to use Filevault, or physically destroy the drive. There are no other options.
"Secure Empty Trash" was deprecated about a decade ago, for sound reasons that existed even before then. The NIST publication Guidelines for Media Sanitization explains.
If your iMac has a Hard Drive or a Fusion Drive instead of just an SSD, then Apple's instructions fall short of securely erasing all your data from a Hard Drive. A Hard Drive requires that every part must be overwritten with a "secure erase" option in Disk Utility.
Or you first need to enable Filevault on the Hard Drive or Fusion Drive. Once the Filevault encryption process has completed....it may take several days with the iMac running 24/7 before the encryption process completes depending on the size & health of the Hard Drive. After the Hard Drive is encrypted, then the instructions provided in the Apple article linked by @den.thed will be sufficient.
If your iMac only has an SSD for internal storage, then the Apple instructions @den.thed provided is sufficient since SSDs work differently than a Hard Drive (or Fusion Drive).
It is unfortunate Apple has such a glaring oversight.
If you have
How do I securely erase my iMac's hard drive before selling it?
