nektos/act
★ 72,381 stars
Covered in week 2026-W34 · the 2026-08 report
Run your GitHub Actions locally 🚀
What act is
When you run act it reads in your GitHub Actions from .github/workflows/ and determines the set of actions that need to be run. It uses the Docker API to either pull or build the necessary images, as defined in your workflow files and finally determines the execution path based on the dependencies that were defined. Once it has the execution path, it then uses the Docker API to run containers for each action based on the images prepared earlier.
From the repository README · read it on GitHub →
Transcript
act runs GitHub Actions locally using Docker containers that replicate the GitHub runner environment including tools and environment variables. This Go binary pulls.github/workflows, builds or pulls required Docker images, and executes each job step-by-step. Test workflow changes before pushing, debug CI failures on your hardware, and replace complex Makefiles with GitHub Actions. Windows and macOS workflows only run on their respective operating systems due to Docker platform constraints. You now catch CI failures before committing.