docker builder prune: Clear BuildKit Build Cache

Clear BuildKit build cache when it eats the runner disk.

docker builder prune removes BuildKit build cache. This page covers full vs dangling-only cleanup and keep-storage limits for CI.

What it does

docker builder prune deletes cached build layers from BuildKit. By default it removes dangling cache; -a removes all build cache. docker buildx prune is the equivalent for a buildx builder instance.

Common usage

Terminal

docker builder prune -f
docker builder prune -af                 # all build cache
docker buildx prune --keep-storage 5GB -f

Common errors in CI

Build cache often dominates "no space left on device" yet is invisible to docker images - check docker system df, then docker builder prune -af. Without -f it prompts and stalls CI. On runners you reuse, prefer --keep-storage to cap cache size rather than wiping it every run, so you keep cache hits while bounding disk.

Related guides

docker system df: See Where Docker Disk GoesHow docker system df works: showing disk used by images, containers, volumes, and build cache, with -v for pe… docker buildx build: BuildKit, Multi-Arch & CacheHow docker buildx build works: BuildKit builds, multi-platform images, --push, and the GitHub Actions cache b… docker system prune: Reclaim Disk in CIHow docker system prune works: removing stopped containers, unused networks, dangling images, and build cache… Docker "no space left on device" - Causes and FixesWhy Docker builds fail with "no space left on device" in CI, and how to reclaim space, prune layers, and stop…