How does CCleaner erase free space?

Open CCleaner, select ‘Tools’ and go to ‘Drive Wiper’. It will take you to a window that asks you to choose ‘Free Space Only’ or ‘Entire Drive’ on the ‘Wipe’ tab. Select ‘Free Space Only’ and then tick the number of drives you want to clean. It will highlight the tab ‘Wipe’ at the bottom.
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