OJBs Web Site: Tip

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Secure Erase SSD

To secure erase an SSD (Ensure its contents cannot be recovered)

The usual secure erase isn't available in Disk Utility.
The old technique is not recommended for SSDs.
Alternative is to decrypt, then re-encrypt the whole drive.

Go to Settings > Security and Privacy > Turn off Filevault
Wait for a long time while the drive is decrypted
Re-enable Filevault and set a new key
Wait for along time again while the drive re-encrypts

A Better Way?

Boot from recovery mode, internet, or external disk
Erase the disk as encrypted HFS or APFS
Supply a complex key
Fill the disk with zeros, using mkfile
Terminal command is mkfile SIZE FILENAME
For example: mkfile 100G File100G
Erase the disk again, without encryption