When files are deleted they are moved to the Trash, and when the Trash is emptied the space they occupied is made free again.
However, the files are still on the disk and could be recovered. This is a security worry if you have any personal files or private documents. So how do you delete files permanently?
OS X had an option to securely empty the Trash, which overwrote files before deleting them, but it was removed in El Capitan. Why? The problem is that securely deleting files only works on mechanical disk drives and not on SSDs, which the newest MacBooks use.
We’ll show how to securely delete files for those with iMacs and MacBooks with mechanical disk drives.
1 Enter Terminal
Click Go>Utilities and double-click Terminal to open it. This is used to enter advanced system commands. Type ‘srm -v ’ with a space after the v (srm = secure remove).
2 Open the Trash
Click the Trash icon in the Dock to open the window and locate a file you want to securely delete. Using this method only one file at a time can be erased, but see the boxout.
3 Drag and drop
Click and hold on the file you want to remove and drag it to the end of the command in the Terminal window. Drop it and the path to the file is automatically entered.
4 Erase the file
Press Enter and you will see a progress counter that runs from 0% to 100%. Delete more files the same way: enter ‘srm -v ’ and drag the file over and drop it, one at a time.