Bun is a single‑binary JavaScript runtime that runs JavaScript and TypeScript on JavaScriptCore, supporting Node.js APIs and existing frameworks. It bundles a package manager, test runner, and bundler, allowing developers to install, test, and build projects without switching tools. What sets Bun apart is its speed: package installation can be up to 30× faster than npm, test runs start in milliseconds, and the built‑in bundler produces single‑file executables. The toolkit also includes a formatter, SQL helper, and WebSocket server, making it a comprehensive solution for modern web development.