Rewriting Bun in Rust
The article discusses the decision to rewrite the Bun runtime, originally built in Zig, using Rust instead. It explores the motivations behind this change, potential improvements in performance and ecosystem compatibility, and the challenges involved in such a significant rewrite of a major JavaScript runtime.
Background
Bun is a popular JavaScript/TypeScript runtime (like Node.js or Deno) created by Jarred Sumner. It was built in **Zig**, a low-level systems language designed for speed and safety. This article discusses the idea of rewriting Bun in **Rust** instead — another systems language known for memory safety and a large ecosystem of tools/libraries.
- Such rewrites matter because moving a major project from one language to another is a huge engineering effort; doing so would signal that Rust's ecosystem (e.g., package management, async support) is more mature than Zig's for this kind of work.
- The context: Node.js (the dominant JavaScript runtime) is written in C++, and Deno (a competitor) is written in Rust. If Bun also moved to Rust, all three major runtimes would be converging on the same language — which could unify development and tooling, or reduce the diversity of approaches.
- As of mid-2026, this is still speculative/hypothetical — no actual rewrite has been announced.