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I have a Macbook with an upgraded, but previously used hard drive.

I know that Macs have an option to 'securely delete' files, which essentially copies over all the file data with random 0's and 1's.

If possible, I would like to do this with all the unused space on my hard drive to clean it up. I think this is similar to what defragmenting does, correct?

Anyway, how can this be accomplished? Is there a way to do so with Disk Utility perhaps? Any help is appreciated!

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migrated from Jan 30 '11 at 3:00

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up vote 3 down vote accepted

It's not quite what defragmentation is. Defragmenting is where fragments of files are placed contiguously so that the drive seek times are reduced, making loading files into memory a little faster.

To do a secure erase of free space on your Mac, do the following in Disk Utility:

Erasing free disk space does not erase the other files on your disk.

  1. In Disk Utility, select the disk or volume in the list with the free space you want to erase.
  2. Click Erase, then click the Erase Free Space button.
  3. Select an option, then click Erase.


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