How to free up Docker disk space on a Mac

See what takes space

Run docker system df for the totals of images, containers, local volumes and build cache, and how much is reclaimable. Add -v for each item.

Prune what isn't used

docker system prune removes stopped containers, networks no container uses, dangling images and unused build cache.
docker system prune -a also removes every image no container uses, not just dangling ones. You'll pull or build them again.
docker system prune --volumes also removes anonymous volumes no container uses.
docker builder prune removes only build cache: dangling cache by default, all unused cache with -a.

Docker asks before it deletes. Space can take a few minutes to show as free on the Mac.

Careful with volumes

Volumes hold data: databases, uploads, anything a container saves. docker volume prune removes unused anonymous volumes. docker volume prune -a also removes named ones, which is where most data lives. Run docker volume ls first, and back up what you need. Nothing pruned goes to the Trash.

Docker Desktop's disk limit

In Docker Desktop > Settings > Resources > Advanced, Disk usage limit sets the most space Docker may use, and Disk image location shows where the disk image is. Lowering the limit deletes the current disk image, with every container and image in it.

The faster way: Caretaker

Caretaker's Developer view shows Docker images, containers, volumes and build cache, with npm, pip, Cargo, Gradle and Homebrew caches. The view is free, and Clean All is in Pro. Docker pruning doesn't go to the Trash, so check volumes before you clean.

Caretaker's Clean page: safe to clear, system junk and creative app caches, in dots.

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Questions

Does docker system prune delete volumes?

Not by default. With --volumes it removes anonymous volumes no container uses.

Why doesn't Docker free space after I delete files in a container?

Space is only freed when images, containers or volumes are removed, for example with docker system prune.