Bun JavaScript Runtime Successfully Rewritten in Rust
Original: Rewrite Bun in Rust has been merged
Why This Matters
Major runtime rewrite demonstrates Rust's growing adoption for system-level tools
Bun has completed a major rewrite of its JavaScript runtime from JavaScript to Rust, with the pull request merged on May 14, 2026. The rewrite reduced binary size by 3-8 MB while maintaining performance.
Bun creator Jarred-Sumner announced the completion of a massive rewrite effort, converting the JavaScript runtime from its original implementation to Rust. The 6,755-commit pull request was merged after passing all existing test suites across platforms. Key improvements include binary size reduction of 3-8 MB, neutral to improved benchmark performance, and elimination of several memory leaks and flaky tests. The rewrite provides compiler-assisted memory safety tools to prevent bugs that previously consumed significant development time. Despite the language change, Bun maintains its core architecture, data structures, and minimal third-party dependencies approach.