Bun JavaScript Runtime Being Rewritten in Rust

Simon Willison's Weblog· July 8, 2026 View original

Summary

The Bun JavaScript runtime is undergoing a complete rewrite using the Rust programming language.

The popular Bun JavaScript runtime is undergoing a substantial architectural shift, with its core components being re-implemented in Rust. This move typically aims to leverage Rust's performance, memory safety, and concurrency benefits. Such a rewrite represents a significant undertaking for the project's development team.

Why it matters

Rewriting a critical runtime in Rust can lead to substantial performance improvements, enhanced security, and better resource utilization, impacting developers who use Bun for their projects.

How to implement this in your domain

  1. 1Monitor Bun's development progress for updates on the Rust rewrite.
  2. 2Evaluate the potential performance and stability benefits for existing Bun-based applications.
  3. 3Consider experimenting with early versions of the Rust-based Bun once available.
  4. 4Assess the implications for developer tooling and ecosystem compatibility.

Who benefits

Software DevelopmentWeb DevelopmentCloud ComputingDevOps

Key takeaways

  • Bun is moving to Rust for core implementation.
  • This rewrite targets performance and safety improvements.
  • Developers should track this significant architectural change.

Original post by Simon Willison's Weblog

"Rewriting Bun in Rust"

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