Act vs regex101

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.

regex101 is Online regex tester and debugger with real-time explanation, match highlighting, and a community library.. It is available under a free model. This tool falls under the developer utilities category.