Act vs Biome

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.

Biome is a fast, unified web toolchain written in Rust that combines linting, formatting, and code analysis for JavaScript, TypeScript, JSON, and CSS. It is the community successor to Rome and aims to replace ESLint and Prettier.