How do I securely erase all data off my Mac?

WARNING

Triple-check that you have everything you need from your Mac before erasing it. We recommend creating a complete clone of your hard drive to insure you have absolutely everything off the computer.

You'll need a Mac operating system disc to securely erase all the information from your Mac. You can use the grey disc that came with your Mac or any OS X upgrade disc that you've purchased since. Secure erasure can take hours, so leave yourself plenty of time or set this up to run overnight.

1. Insert the operating system disc into your Mac and then restart the computer. While the Mac is starting up, hold down the "c" key to tell the Mac to startup from the disc. (This can take a few minutes longer than starting up your computer normally, so be patient.)
2. After you select your language do NOT proceed to install or upgrade Mac OS X. Instead go to the Utilities menu and select Disk Utility. If you don't see a Utilities menu, check under the Installer menu for Open Disk Utility.
3. In Disk Utility's left bar you'll see all the hard drives installed or attached to your Mac. Make sure to select the correct hard drive you want to erase. Your hard drive will be listed twice, first by its technical name (e.g. 74.5GB Toshiba MK80..) and under that you'll see the name that appears on your desktop (e.g. Macintosh HD). Select the top listing with the technical name of the hard drive, as shown in the screen shot below.
4. Select the Erase pane from the upper center options.
5. In the lower right, press the Security Options... or Options... button.
6. Select the level of security you would like to erase the computer with. Selecting Zero Out Data will prevent anyone but a data recovery expert from accessing your data. For additional security, use one of the multiple pass erasure options to prevent any chance of your data being recovered. Keep in mind that a 7-Pass Erase will take 7 times as long.
7. Press the Erase... button in the lower right corner. It will warn you that your data is going to be completely erased, click Erase to confirm.

After the erasure is finished your Mac will be completely blank (you won't be able to use it.) Check out our instructions for reinstalling Mac OS X if you are giving away or selling the Mac. 

Published April 29, 2009 5:41 PM
Last modified on June 16, 2009 5:15 PM