Bun (software)

Bun is a JavaScriptruntime, package manager and test runner designed as a drop-in replacement for Node.js. Bun uses Safari's JavaScriptCore as its JavaScript engine, unlike Node.js and Deno, which run on the V8 engine used by Chromium.

Bun was originally developed by Jarred Sumner, with its initial release in September 2021. It was acquired by Anthropic in December 2025.