Act vs imgix

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.

imgix is a developer-utilities tool that image processing and cdn service that transforms, optimizes, and delivers images via url parameters. It offers a paid pricing model.