Bun 1.4 is here with a complete rewrite in Rust, delivering substantial improvements across performance, compatibility, and stability. The update squashes over 2,900 issues and represents a major leap forward for developers looking to move away from traditional Node.js setups.
The headline win is compatibility: some Bun modules now pass more than 97% of official Node.js tests, making it a genuinely viable drop-in replacement for many projects. On the performance front, the gains are striking. CPU idle usage drops by up to 5 times, HTTP server applications use 13% to 48% less memory, and startup times improve dramatically—2.5 times faster on Windows and 2 times faster on Linux in development environments.
These improvements matter in production. Lower memory footprint means denser deployments and smaller bills. Faster startup times reduce cold-boot penalties on serverless platforms. The massive compatibility jump removes one of the biggest friction points for teams considering a migration from Node.js. For developers already using Bun or evaluating it, version 1.4 makes a compelling case.