Bun, an all-in-one toolkit for building, testing, debugging, and running JavaScript and TypeScript apps, has reached stable production-ready status as of September 8.

Positioned as a drop-in replacement for Node.js, Bun is a single executable intended to eliminate complexity and slowness without tossing away everything that is “great” about JavaScript, Bun’s developers said. They bill Bun as a fast JavaScript runtime that simplifies JavaScript development by eliminating the “layers and layers of tooling that have accumulated on top of each other.”

Bun makes Node.js tools including node, npx, nodemon, and dotenv or cross-env unnecessary, the Bun team said. And Bun can run .js, .ts, .cjs, .mjs, .jsx, and .tsx files, which can replace transpilers such as tsc and babel. For testing, Bun is a Jest-compatible test runner supporting snapshot testing, code coverage, and mocking. Bun also serves as a JavaScript bundler with “best-in-class” performance and an esbuild-compatible plugin API. It also is an NPM-compatible package manager.

Other features of Bun:

• A JavaScript transpiler is baked into the runtime, for running JavaScript, TypeScript, and JSX/TSX files, with no dependencies.
• ECMAScript and CommonJS module systems are supported.
• Web-standard APIs are supported such as fetch, request, and WebSocket. Bun APIs were designed to be easy to use and fast.
• Bun is faster than npm, yarn, and pnpm, the Bun team said. A global module cache is used to avoid redundant downloads from the NPM registry; the fastest system calls are used from each operating system.
• Hot reloading is enabled, to reload an application when files change.

Production-ready native builds of Bun are provided for macOS and Linux; an experimental native build of Bun for Windows also is available. Bun can be installed with the following command:

$ curl -fsSL https://bun.sh/install | bash

Upgrades can be done by running bun upgrade.