Mac storage basics · Checking your storage
Why does Finder show a different amount of free space than Storage settings or Disk Utility?
Short answer: Finder and Storage settings count purgeable space (snapshots, cached cloud files) as available; Disk Utility's Free figure and df count only space that is free right now.
They count different things. Finder and Storage settings usually report available space, which includes space macOS could free on its own (purgeable space: local snapshots, cached cloud files and caches). Disk Utility can show both Available and Free, and command-line tools such as df show only what is free right now.
So a Mac can say "120 GB available" in Finder while only 70 GB is genuinely free this second — the other 50 GB is held by things macOS will release when it needs room.
This matters when an installer or a big copy checks the real free figure and refuses even though Finder looks fine. Storage Studio works from the figure your Mac will actually hand out and, where the two differ, shows both. See purgeable space.