BuildKit is an improved backend to replace the legacy builder. BuildKit is the default builder for users on Docker Desktop, and Docker Engine as of version 23.0.

BuildKit provides new functionality and improves your builds' performance. It also introduces support for handling more complex scenarios:

  • Detect and skip executing unused build stages
  • Parallelize building independent build stages
  • Incrementally transfer only the changed files in your build context between builds
  • Detect and skip transferring unused files in your build context
  • Use Dockerfile frontend implementations with many new features
  • Avoid side effects with rest of the API (intermediate images and containers)
  • Prioritize your build cache for automatic pruning

Apart from many new features, the main areas BuildKit improves on the current experience are performance, storage management, and extensibility. From the performance side, a significant update is a new fully concurrent build graph solver. It can run build steps in parallel when possible and optimize out commands that don't have an impact on the final result. We have also optimized the access to the local source files. By tracking only the updates made to these files between repeated build invocations, there is no need to wait for local files to be read or uploaded before the work can begin.


At the core of BuildKit is a Low-Level Build (LLB) definition format. LLB is an intermediate binary format that allows developers to extend BuildKit. LLB defines a content-addressable dependency graph that can be used to put together very complex build definitions. It also supports features not exposed in Dockerfiles, like direct data mounting and nested invocation.

Everything about execution and caching of your builds is defined in LLB. The caching model is entirely rewritten compared to the legacy builder. Rather than using heuristics to compare images, LLB directly tracks the checksums of build graphs and content mounted to specific operations. This makes it much faster, more precise, and portable. The build cache can even be exported to a registry, where it can be pulled on-demand by subsequent invocations on any host.

LLB can be generated directly using a golang client package that allows defining the relationships between your build operations using Go language primitives. This gives you full power to run anything you can imagine, but will probably not be how most people will define their builds. Instead, most users would use a frontend component, or LLB nested invocation, to run a prepared set of build steps.


A frontend is a component that takes a human-readable build format and converts it to LLB so BuildKit can execute it. Frontends can be distributed as images, and the user can target a specific version of a frontend that is guaranteed to work for the features used by their definition.

For example, to build a Dockerfile with BuildKit, you would use an external Dockerfile frontend.

Getting started

BuildKit is the default builder for users on Docker Desktop and Docker Engine v23.0 and later.

If you have installed Docker Desktop, you don't need to enable BuildKit. If you are running a version of Docker Engine version earlier than 23.0, you can enable BuildKit either by setting an environment variable, or by making BuildKit the default setting in the daemon configuration.

To set the BuildKit environment variable when running the docker build command, run:

$ DOCKER_BUILDKIT=1 docker build .


Buildx always uses BuildKit.

To use Docker BuildKit by default, edit the Docker daemon configuration in /etc/docker/daemon.json as follows, and restart the daemon.

  "features": {
    "buildkit": true

If the /etc/docker/daemon.json file doesn't exist, create new file called daemon.json and then add the following to the file. And restart the Docker daemon.


BuildKit only fully supports building Linux containers. Experimental Windows container support is tracked in moby/buildkit#616