act Cheatsheet

Q: What Docker image does act use?

act uses `catthehacker/ubuntu:act-latest` by default. You can customize per platform with `-P ubuntu-latest=myimage:tag`. For arm64 hosts, use `--container-architecture linux/arm64`.

Q: How do I pass secrets to act?

Use `-s MY_SECRET=value` for inline secrets, or `--secret-file .secrets` for a file with one KEY=value per line. For GitHub Actions variables (not secrets), use `--var MY_VAR=value`.

Q: How do I speed up repeated act runs?

Use `--reuse` to keep containers between runs, `--pull=false` to skip pulling new images. You can also specify a custom runner image with `-P` that includes your dependencies.

act runs GitHub Actions workflows locally without pushing to GitHub. Validate your CI/CD pipelines instantly, debug faster with local Docker-based execution. It supports all common event types.

Updated: 2026-07-20·22 commands

Quick Start

bash
act                          # Run all workflows (push event)
act -l                       # List all workflows
act -j build                 # Run a specific job
act pull_request             # Simulate PR event
act --secret-file .secrets   # Load secrets from file
act --reuse                  # Reuse containers for speed

Install & Setup(3)

Command	Level	Example
`act --help` Show act help	Basic	`act --help`
`act --version` Show act version	Basic	`act --version`
`.actrc` Default act config file (project root or ~/.actrc)	Intermediate	`# ~/.actrc -P ubuntu-latest=catthehacker/ubuntu:act-latest --pull=false`

Basic Usage(7)

Command	Level	Example
`act` Run all workflows (default trigger: push)	Basic	`act`
`act -l` List all available workflows and their events	Basic	`act -l`
`act -g` Display workflow structure as a graph	Basic	`act -g`
`act -j` Run a specific job (not the entire workflow)	Basic	`act -j test`
`act -W` Specify a workflow file or directory	Basic	`act -W .github/workflows/ci.yml`
`act --defaultbranch` Specify the default branch name (default: main)	Intermediate	`act --defaultbranch master`
`act --container-architecture` Specify container architecture (e.g., linux/amd64, linux/arm64)	Intermediate	`act --container-architecture linux/amd64`

Event Triggers(4)

Command	Level	Example
`act pull_request` Run workflows simulating a pull_request event	Basic	`act pull_request`
`act push` Run workflows simulating a push event	Basic	`act push`
`act schedule` Run workflows simulating a schedule event	Intermediate	`act schedule`
`act workflow_dispatch` Run workflows simulating a workflow_dispatch event	Intermediate	`act workflow_dispatch`

Secrets & Env(4)

Command	Level	Example
`act -s` Set a secret (multiple -s flags allowed)	Intermediate	`act -s MY_SECRET=value`
`act --secret-file` Load secrets from a file (one KEY=value per line)	Intermediate	`act --secret-file .secrets`
`act --env-file` Load environment variables from a file	Intermediate	`act --env-file .env`
`act --var` Set GitHub Actions variables	Intermediate	`act --var MY_VAR=value`

Advanced(4)

Command	Level	Example
`act -P` Custom platform-to-image mapping (for newer versions)	Expert	`act -P ubuntu-latest=catthehacker/ubuntu:act-latest`
`act --pull=false` Disable pulling new Docker images (use cached)	Intermediate	`act --pull=false`
`act --reuse` Reuse containers from the previous run (faster debugging)	Intermediate	`act --reuse`
`act --bind` Bind mount the working directory into the container (instead of copy)	Expert	`act --bind`

FAQ

What Docker image does act use?

How do I pass secrets to act?

How do I speed up repeated act runs?

This cheatsheet is compiled from official tool documentation. Last updated: 2026-07-20.