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How to Securely Wipe a Hard Drive on Your Mac

During a junk room cleaning session, I came across a bunch of older hard drives that I wanted to give away… but what if they have my personal data on them? The answer is to securely wipe them, and on Mac OS X it couldn’t be simpler.

If you were running Windows, you can completely destroy your hard drive data using the boot and nuke CD, but since I’m not running Windows on this computer, I decided to use the built-in tools on OS X to get the job done.

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Using Disk Utility to Securely Wipe a Hard Drive

First you’ll want to open up Disk Utility, which you can find in the Applications / Utilities folder, but it’s much easier to just do a Spotlight search to bring it up. Once you’ve done so, you’ll see the hard drive in the list, and once you click on it, you will find an Erase tab.

The important item on this page is the Security Options button, which gives you better options than just formatting the drive, which leaves your hard drive open to people using recovery tools.

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Once you pop open the Secure Erase Options dialog, you can choose how securely you want to erase the drive. The default (fastest) is to just reformat the partition table, but you probably don’t want to do that unless you are certain you’ve never had any sensitive files on the drive. The “Most Secure” option is going to overwrite the drive 7 times to comply with government standards, but that’s also quite unnecessary since you only need to wipe a drive once to really secure the drive.

Your best bet is the second notch, which will write a single pass of zeros over the entire disk, which will be the fastest way to securely wipe your drive — although if you have a large hard drive, it will still take a very long time.

Once you’ve selected this option and moved on to the Erase button, you’ll be prompted whether you really want to erase the drive — it’s worth noting at this step that you should have clicked on the drive in the left-hand panel, not the partition. You don’t want to wipe just a partition, make sure you are wiping the whole drive.

Click the Erase button again, and you’ll be forced to sit there and wait for the erase to fully complete. It’s going to take a long time unless the drive is really small. If you change your mind in the middle, you’ll be able to click a Skip button that’ll just reformat the drive, but if you’ve had sensitive data on that drive, you should really wipe it properly.

Or get a giant hammer and smash it to bits. That’ll work too.

Lowell Heddings, better known online as the How-To Geek, spends all his free time bringing you fresh geekery on a daily basis. You can follow him on if you'd like.

  • Published 01/24/14

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