Why your Mac still says the disk is full after you delete files
Because the space is usually held by Time Machine local snapshots, not by the files you deleted. macOS snapshots your disk hourly even with no backup drive attached, and a snapshot pins every block that existed when it was taken.
- macos
- storage
- troubleshooting
You delete 20 GB. You empty the Trash. Finder still says the disk is full. Nothing you remove seems to change the number.
This is not a bug, and the files really are gone. The space is being held by something else.
The short answer
Time Machine local snapshots. macOS takes hourly snapshots of your disk on the disk itself, even when no backup drive is attached. A snapshot pins every block that existed at the moment it was taken. Delete a file afterwards and the file disappears from your view, but the blocks stay allocated because a snapshot still refers to them.
macOS expires these on its own within roughly 24 hours, or sooner when free space runs low. That is why the space sometimes "comes back by itself" overnight.
The three usual causes
1. Local snapshots
List them:
tmutil listlocalsnapshots /
Each line is a snapshot holding space. macOS removes them automatically, and you can remove one immediately with tmutil deletelocalsnapshots <date>. Your real Time Machine backups on an external disk are not affected.
2. Purgeable space
macOS reports two different numbers. Finder counts space as used; About This Mac counts some of it as available. The gap is "purgeable" — space the system will release on demand, held by snapshots, cached iCloud files and other content it can drop.
You cannot delete purgeable space directly, and you do not need to. It is released when something actually needs the room. It does, however, make every storage figure look wrong until you know it exists.
3. A Docker disk image
Docker keeps every image, container and volume inside one virtual disk file. That file grows as you use Docker and never shrinks on its own. Deleting images inside Docker frees space in the VM and leaves the file exactly as large on your Mac.
docker system prune -a --volumes
Then let Docker Desktop reclaim the file.
Why Finder cannot tell you this
Finder shows you a filesystem tree. None of these three things is a file in that tree: a snapshot is filesystem metadata, purgeable space is an accounting policy, and the Docker image is one opaque file whose size has nothing to do with its contents.
So the honest answer to "what is taking my space" often is not a folder at all — which is why deleting folders does not fix it.
Checking all three at once
Reclaim has a doctor command that reports exactly these:
reclaim doctor
It prints total, actually-free and available-including-purgeable, then lists any snapshots, the purgeable pool and any oversized VM disk images, with what each one is and whether removing it helps.
