GitHub Actions - Do you test workflows locally with act?

Pushing small GitHub Actions changes just to see whether a workflow works is slow, noisy, and burns hosted runner minutes unnecessarily.

act solves a lot of that pain by running your GitHub Action workflows locally. It shortens the feedback loop when you are iterating on workflow logic, shell steps, environment variables, or basic job wiring.

❌ Figure: Bad example - Bad example - Using hosted runners as your first feedback loop

✅ Figure: Good example - Good example - Use act to tighten the workflow feedback loop

Why act is useful

• Faster iteration - Catch broken paths, missing environment variables, and shell mistakes without waiting on GitHub
• Cheaper experimentation - Avoid burning hosted runner minutes for every small workflow tweak
• Less noisy history - Reduce the stream of tiny "fix workflow" commits made purely to test YAML changes

act gets you closer to your final workflow much earlier, but it is still not identical to running on GitHub's hosted runners. Some workflows behave differently depending on the runner image, available tools, service containers, or platform-specific behaviour.

That means act should improve your inner loop, not replace your real CI run. You can read more about act via the act documentation.