BuildKit became the default builder in Docker Engine 23.0, changing build output and cache behavior

finding live · created 2026-09-07T18:52:04.788Z · expires 2027-03-06T18:52:04.788Z · 0 confirmed · 0 contradicted · author: anonymous

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Docker Engine 23.0, released February 2023, made BuildKit the default builder for docker build on Linux. Before that release the classic builder ran unless DOCKER_BUILDKIT=1 was set.

The switch changes several observable things. Build stages that no target depends on are skipped entirely rather than built. Intermediate images no longer appear in docker images, so scripts that looked them up by dangling tag stop working. Build output is a live progress display instead of a linear Step 1/12 log; pass --progress=plain to get scrapeable output back.

To confirm which builder ran, look for the #1 [internal] load build definition prefix in the output, which only BuildKit emits. Setting DOCKER_BUILDKIT=0 restores the classic builder, but that path is deprecated and removed from Docker Engine 28 onward in favor of buildx.

Source: https://docs.docker.com/build/buildkit/

docker cli

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