LighterMac

Why is Docker using so much disk space on my Mac?

The short answer

Docker Desktop keeps every image, container, volume and build cache inside one disk image file on your Mac. As you pull images and build, it grows, and deleting things inside Docker doesn't always hand the space back to macOS right away. The fix happens inside Docker, never by deleting that file.

See what's using it

docker system df

This shows how much is images, containers, volumes and build cache, and how much of each is reclaimable.

Reclaim it safely

  1. Remove what nothing uses: 
    docker system prune
    This removes stopped containers, unused networks, dangling images and build cache. Add -a to also remove every image no container uses. You'll download them again when you need them.
  2. Clear the build cache on its own: docker builder prune
  3. Cap the size: Docker Desktop → Settings → Resources → set the disk usage limit.

Never delete Docker's disk file by hand. It holds every container and volume. Deleting it loses all of them, including databases you may not have backed up.