Freeing up space · Free Up Space wizard and button
Does freeing space by moving a folder keep a second copy on my Mac?
Short answer: No. It's a move, not a copy: after the copy is verified, the data lives only on your fast drive and links stay in its place. Back up that drive like any drive holding your only copy.
No. Moving a folder is a move, not a copy — that's the whole reason the space comes back. Once the move is verified, the original on your built-in drive is replaced with links and the only copy of the data lives on your fast drive.
That's why it's worth having your own backup of the fast drive, the same as you would for any drive that holds the only copy of something. Storage Studio's backup features and Time Machine can both help — see the Backups FAQ.
If you want the folder back on your Mac, use Move back in What's Using Space.