BuildKit

BuildKit is a concurrent, cache-efficient, and Dockerfile-aware container image builder that serves as the default build engine for Docker (replacing the legacy builder since Docker Engine 23.0). Developed by the Moby Project (the open-source community behind Docker), BuildKit was created to address the performance and functionality limitations of the original Docker build system, introducing significant improvements in build speed, caching, and extensibility. Key innovations include: concurrent build step execution (BuildKit can execute independent build stages in parallel, dramatically reducing total build time for multi-stage Dockerfiles), an improved caching architecture that caches build results at the instruction level rather than the layer level, allowing more granular cache hits and misses, support for multiple cache backends including inline cache, registry mirror cache, local directory cache, and remote cache exporters/importers, a new LLB (Low-Level Build) graph format that represents build steps as a directed acyclic graph (DAG) for more efficient dependency resolution and parallel execution, support for frontend extensions (custom Dockerfile syntax, build args, and secrets), built-in support for multi-platform builds (building images for linux/amd64, linux/arm64, and other architectures simultaneously using QEMU emulation or cross-compilation), SSH agent forwarding for secure credential handling during builds, secret mounting for securely passing sensitive data (like API keys and npm tokens) into build steps without exposing them in image layers or build logs, and a daemon-less mode via buildctl for integrating BuildKit into CI/CD pipelines without running a background daemon. As of 2026, BuildKit has over 8,100 GitHub stars.