Act vs DevContainers

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.

DevContainers Open specification for defining reproducible development environments using Docker containers, supported by VS Code and GitHub Codespaces.