I have a Late-2015 Apple iMac with 1 TB HDD.

Since it's not being used, was thinking of selling it.

Did some reading online and seems that there are many ways the data can be recovered.

How can we ensure the data is completely gone and unrecoverable? So that the new owner cannot access.

  • If you are using FileVault already, then your data is encrypted and can't be recovered, so there's no need to do multiple erases (which may stress an ageing HD). Also, buying old Macs in the hope that you can recover some data that might be profitable is not .... well, profitable.
    – benwiggy
    Feb 10 at 12:14

1 Answer 1


Disk Utility has a secure erase function.

  1. Open Disk Utility
  2. Select the disk that you wish to erase
  3. Select the Erase tab
  4. Click on the Security Options... button
  5. Move the slider to Most Secure
  6. Click the OK button

This screen shot is for Disk Utility, version 13 (517), that comes with Mavericks (OS X 10.9.5), later versions may vary in appearance:

Secure Erase dialog

This will securely erase the disk. As you have selected the most secure option, this may take a while.

This option states:

This option meets the US Department of Defense (DOD) 5220-22M standard for securely erasing magnetic media. It erases the information used to access your files and writes over the data 7 times.

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