Freeing up space · Stopping, undoing and apps in the way
What happens if my Mac shuts down in the middle of a clear-up?
Short answer: It's resolved at the next launch: anything whose copy completed goes into the Recycle Vault, and anything unfinished is undone with the original left in place. Nothing is reported removed while still on disk.
Storage Studio sorts it out at the next launch. It checks what was in progress: anything whose recoverable copy completed is added to the Recycle Vault so you can find it, and anything whose copy didn't finish is undone, leaving the original where it was.
Nothing is ever reported as removed while it's still on your disk. Moves work the same way: if you quit or restart mid-move, Storage Studio re-attaches to it, and an incomplete copy is cleaned off the fast drive rather than the original. See what happens if a move fails partway.