act

Run the default workflow

$ act

$ act -l

$ act -W [.github/workflows/ci.yml]

$ act -j [build]

$ act --secret-file [.secrets]

act [-W workflow] [-j job] [-e event] [--secret-file file] [options]

act allows you to run GitHub Actions workflows locally using Docker containers. It parses workflow YAML files and executes jobs in containers that simulate the GitHub Actions environment, enabling rapid iteration and debugging without pushing to GitHub.
The tool supports most GitHub Actions features including matrix builds, secrets, environment variables, and artifacts. It downloads and caches action repositories automatically.

-W file, --workflows file

Path to workflow file(s) (default: .github/workflows/)

Run a specific job

Path to event JSON file

Load secrets from file (KEY=VALUE format)

Set a secret (KEY=VALUE)

Load environment variables from file

Custom Docker image for platform (e.g., ubuntu-latest=nektos/act-environments-ubuntu:18.04)

List available workflows and jobs

Show what would be run without executing

Reuse containers between runs

Bind working directory instead of copying

Container architecture (amd64, arm64)

~/.actrc

User-level default flags applied to every act invocation. Each line contains a single command-line flag (e.g., `-P ubuntu-latest=catthehacker/ubuntu:act-latest`).

Project-level defaults, same format as the user-level file. Overrides user-level settings when present.

Not all GitHub Actions features are supported; some hosted runner features like service containers have limitations. Large workflow images can be slow to download initially. Some actions may behave differently locally than on GitHub. Docker must be running.

act was created by Casey Lee (nektos) and first released in 2019. It was developed to address the slow feedback loop of GitHub Actions by enabling local execution. The project quickly gained popularity in the CI/CD community.

docker(1), gh(1), make(1)