Freeing up space · Where your space went
Why does Storage Studio sometimes show less free space than Finder?
Short answer: Finder counts space held in automatic backups as free; the breakdown also shows what your Mac would hand out right now. Where they differ, Storage Studio shows both. The gap is usually held snapshot space.
Because there are two honest ways to count free space on a Mac. Finder's figure counts space held in automatic backups as though it were free, since your Mac would release it if needed. The other figure is what your Mac would actually hand out right now.
Storage Studio's chart draws the first, matching Finder. The space breakdown works from the second, because that's the one that decides whether you can save a file. Where they differ, the panel says so and shows both rather than quietly picking one. The gap is usually space held in local snapshots — see held space.