What is BuildKit?

BuildKit is a modern build engine for Docker that speeds up image creation, makes builds more efficient, and adds new features like parallel processing and better caching. It works behind the scenes to turn your Dockerfile instructions into a runnable container image.

Let's break it down

  • Build engine: the part of Docker that reads a Dockerfile and actually does the work of creating an image.
  • Docker: a platform that packages software into containers, which are lightweight, portable units.
  • Speeds up image creation: it finishes the build faster than the older Docker builder.
  • More efficient: uses resources (CPU, disk, network) smarter, so you waste less time and money.
  • Parallel processing: runs independent steps at the same time instead of one after another.
  • Better caching: remembers results of previous steps so it can skip work that hasn’t changed.

Why does it matter?

Faster builds mean developers spend less time waiting and can ship updates quicker. Efficient builds lower cloud costs and make continuous-integration pipelines smoother. Better caching also reduces network traffic and storage use, which is good for both small teams and large enterprises.

Where is it used?

  • CI/CD pipelines (e.g., GitHub Actions, GitLab CI) to compile and push Docker images rapidly.
  • Large microservice architectures where many services are built daily and need quick turnaround.
  • Edge or IoT device builds that run on limited hardware, benefiting from the reduced resource footprint.
  • Development environments like VS Code Remote Containers, where instant rebuilds improve the coding experience.

Good things about it

  • Significantly faster builds thanks to parallel execution.
  • Advanced caching that can reuse layers across different builds and even different machines.
  • Lower memory and CPU usage compared to the classic builder.
  • Supports new Dockerfile syntax (e.g., RUN --mount=type=cache) for more control.
  • Easy to enable with a single environment variable (DOCKER_BUILDKIT=1).

Not-so-good things

  • Some older Docker versions or third-party tools may not fully support BuildKit yet.
  • Debugging build failures can be harder because the output is more compact and parallelized.
  • Certain legacy Dockerfile patterns need to be rewritten to take full advantage of the new features.
  • Enabling BuildKit may expose new security considerations, such as handling of secret mounts, which require careful configuration.