Overview

"Think globally, act locally"

Run your GitHub Actions locally! Why would you want to do this? Two reasons:

Fast Feedback - Rather than having to commit/push every time you want to test out the changes you are making to your .github/workflows/ files (or for any changes to embedded GitHub actions), you can use act to run the actions locally. The environment variables and filesystem are all configured to match what GitHub provides.
Local Task Runner - I love make. However, I also hate repeating myself. With act, you can use the GitHub Actions defined in your .github/workflows/ to replace your Makefile!

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Now Manage and Run Act Directly From VS Code!<br/>
Check out the GitHub Local Actions Visual Studio Code extension which allows you to leverage the power of act to run and test workflows locally without leaving your editor.

How Does It Work?

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. The environment variables and filesystem are all configured to match what GitHub provides.

Let's see it in action with a sample repo!

Demo