Freeing up space · Local snapshots and held space
How does Storage Studio treat purgeable space?
Short answer: Purgeable space is room macOS keeps in reserve — mostly local snapshots — and frees on demand. Storage Studio shows it as its own line and lets you release it now in Local Snapshots.
Purgeable space is room macOS is keeping in reserve — mostly local snapshots and some caches — that it frees automatically when something needs it. It can make your free space look larger or smaller than you expect.
Storage Studio names it rather than lumping it into "other": the space breakdown shows space held by automatic backups as its own line, and the Local Snapshots window lets you turn some of it into space you can use right now. Note that because Finder already counts purgeable space as free, releasing it doesn't always raise the figure Finder shows — see two free-space numbers.