Act vs Chromatic

act is an open-source command-line tool that runs GitHub Actions workflows locally using Docker containers. It reads workflow files from .github/workflows/ and executes them with environment variables and filesystem configurations matching GitHub's hosted runners. The tool enables fast local feedback on workflow changes without requiring commits and pushes to a remote repository.

Chromatic is a visual testing and review platform for UI components built on Storybook. It provides automated visual regression testing, component documentation, and a review workflow for design systems.