There are three different erasure options available to you which are Fastest, Secure, and Most Secure.

Pick the level of erasure you want and then click the Erase free space to start the overwriting process on the hard drive’s vacant spaces.

Click the Erase free space button after opening the Erase tab.If the hard drive whose free spaces you want to erase is an external hard disk then you would have to connect it to the Mac and then select it from the menu located on the left-hand side of the screen.You can use the Launchpad for launching this app as well. This app is located in the utility menu which can itself be found in the Applications menu. The initial step is to start the Disk Utility app.However, do keep in mind that this method for free space erasure is only applicable for traditional hard drive and won’t work on SSD versions that utilize flash memory. It offers you the chance to overwrite on the free space left on your hard disk so that no one can retrieve the data that was previously stored on it. You will have to use the Disk Utility app provided by your Mac OS X to erase free space on Mac hard drive. Part 1: How to Erase Free Space on Hard Drives in Mac OS X However, make sure that the erasure is done securely without damaging the hard disk. Now, if you are selling the hard drive of your Mac and don’t want the person buying it to recover the documents that you deleted then you must erase free space on Mac hard drive. However, if this free space doesn’t get overwritten, then it can be used to retrieve the previous data that it held using a data recovery tool.

This free space can be utilized for storing other data. Every time you delete any file or document on the Mac hard drive it creates free space.

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