Zero-Format (Secure Erase)

I personally do not trust any shipped Hard Drive including ones shipped with brand new CPU. Zero-formatting (low-level format for SCSI) Hard Drive will map out bad sector, and will save steps of troubleshooting down the load.

  1. Go to Application Folder > Utilities Folder
  2. Launch Disk Utility Application
    Alternatively, open Spotlight with Cmd+Space then start type Disk U... then Disk Utility will be listed for your to open there.
  3. Click on [Erase] Tab
  4. Select the drive you with to format
  5. Choose Format type to Mac OS Extended (Journaled)
  6. Click on the Security Options button
  7. Select Zero Out Data option

IMPORTANT: Do not zero-format if SSD and/or Fusion Drive. Zero-formatting could damage the drive or shorten the life of the drive.

El Capitan

El Capitan Disk Utility removed zero-formatting option probably due to the increase of SSD and Fusion Drive out there. You can still run zero-formatting from terminal by running the command as follows:

diskutil secureErase freespace 1 /dev/{your target disk ID}

As you can see, you will need to find out what is the disk ID you want to run zero-formatting (now called Secure Erase). Run this command to find out:

diskutil list