How to Wipe a Hard Drive on a Mac

By Contributing Writer

To protect your confidential files, take the time to properly wipe your hard drive before selling or giving away your computer. Simply deleting files and emptying your Mac's trash is not enough; this information can easily be restored using widely available software. Fortunately, you can use your Mac's Disk Utility to securely wipe all information from your hard disk.

Things You'll Need

  • Start-up disk (either Mac OS X Install CD or Software Restore CD)

Getting Started

Step 1

Insert your Mac OS X Install or Software Restore CD into your your computer's disk drive, and restart your computer, holding down the "C" button.

Step 2

Choose your preferred language and click "Continue."

Step 3

From the menu bar in the Mac OS X Installer window, choose "Disk Utility."

Step 4

On the left-hand side of the Disk Utility window, select your hard drive, and on the right, choose the "Erase" tab.

Step 5

From the "Volume Format" drop-down, choose the "Mac OS Extended (Journaled)" option.

Step 6

Type a new name for your hard drive in the "Name" field and click the "Security Options" button.

Step 7

From the Secure Erase Options, choose either the "7-Pass Erase" or the "35-Pass Erase". Both options will overwrite your data with zeroes several times, and both provide a very high level of security. Click "OK."

Step 8

Click "Erase," and confirm that you want to erase the drive. Wait while Disk Utility unmounts, erases and renames your hard drive. This will take several hours if you chose the 7-Pass option, or nearly a day if you chose the 35-Pass option.

Tips & Warnings

  • The 7-Pass option is compliant with the security standards of the U.S. Department of Defense.The 35-Pass option uses a Gutmann algorithm to obliterate files, and is suitable for the most sensitive information.
  • This procedure will erase your hard drive so that the files cannot be recovered. Make copies of any important files on another disk before you begin.