
Choose Apple menu > System Settings > General > Storage.Keep in mind that the latter two options take longer to complete, because they are performing the same overwrite task either 3 times or 7 times.Also Read: How to Free Up Space on Mac How to Check System Data Storage on Macīefore understanding what System Data storage is, let's check how much space it is using on your Mac. Most Secure – The most secure option that also takes the longest, this writes data over the free space a total of 7 times.Ĭhoose whichever option is most appropriate for your needs, but it's generally recommended to use the "secure" or "most secure" option if you intend on transferring ownership of a hard drive, or if you suspect a hard drive that once contained important data has the chance of being stolen or misused.


Erasing Free Space on Hard Drives in Mac OS X This option is not available for flash-memory based SSD models (like those bundled within the MacBook Air, Retina MacBook Pro) because those drives use the TRIM function to quickly remove and recover blocks instead, which has the side effect of automatically preventing file recovery fairly quickly – often within 10 minutes of emptying the Trash. This only works on traditional hard drives of the spinning platter variety, which is typical for MacBook Pro, Mac Mini, and iMac models, and is the case with most external hard drives used for backups. The Mac OS X Disk Utility app provides an ability to erase free space on traditional hard drives, which overwrites vacant disk space on the drive to prevent any potential recovery of deleted files (that is, files that have been removed traditionally, rather than through secure methods).
