Bun - The JavaScript Runtime used by All (Cool Cats)

Bun is a fast JavaScript runtime. It's website is bun.sh (where the suffix sh denotes a St Helena domain). Bun is built from scratch to "serve the modern JavaScript ecosystem".

A major selling point of Bun is it starts fast and runs fast. It extends the performance-minded JS engine built for Safari known as JavaScriptCore. Fast start times leads to fast apps like Claude Code CLI.

Bun also boasts "cohesive DX" (developer experience) with a package manager, test runner and bundler all included.

Design-wise it has been designed to be a drop-in replacement for Node.js. Thousands of Node.js and Web APIs have been implemented in Bun like fs, path and Buffer.

Bun's ambition is to run most of the world's server-side JavaScript.