Bun ditches Zig for Rust to boost performance

#programming #devops #webdev #tech

TL;DR

Bun was initially written in Zig and has gained significant traction with over 22 million monthly downloads.
The project's scope has also presented challenges for stability, with numerous bugs fixed in recent versions.
Rewriting Bun in Rust is a significant undertaking, with the potential to improve performance and reliability.
Bun's acquisition by Anthropic in December 2025 may influence the project's future development and direction.

Bun's journey began as a line-for-line port of esbuild's JavaScript and TypeScript transpiler from Go to Zig, with the first line of Zig written on April 16, 2021. The project's massive scope includes a JavaScript, TypeScript, and CSS transpiler, minifier, and bundler, as well as an npm-compatible package manager and Jest-like test runner. The initial version of Bun was written by a single person in just one year, a feat made possible by the use of Zig.

What the data shows

The data shows that Bun has experienced significant growth, with its CLI receiving over 22 million monthly downloads. Popular tools like Claude Code and OpenCode have also bet on Bun as their runtime, and companies like Vercel, Railway, and DigitalOcean have implemented first-party support for Bun. However, the project's scope has also presented challenges, with numerous bugs fixed in recent versions, including heap-use-after-free crashes, use-after-free crashes, and memory leaks.

What this means for tech readers

For tech readers, the rewriting of Bun in Rust is a significant development that may improve the project's performance and reliability. The use of Rust could provide better memory safety and concurrency support, addressing some of the challenges faced by the current Zig implementation. Additionally, the acquisition of Bun by Anthropic in December 2025 may bring new resources and expertise to the project, potentially accelerating its development and adoption.

What to do right now

For those interested in Bun, now is a good time to explore the project's current capabilities and limitations. The primary source article provides a detailed overview of the project's history, scope, and challenges, as well as the motivations behind the decision to rewrite it in Rust. Readers can also visit the Bun website to learn more about the project's features and use cases, and to stay up-to-date with the latest developments.

Bottom line

In summary, the rewriting of Bun in Rust is a significant undertaking that may improve the project's performance and reliability. With its massive scope and significant traction, Bun has the potential to become a major player in the tech industry. As the project continues to evolve, it will be interesting to see how the use of Rust and the acquisition by Anthropic influence its development and adoption.

Frequently asked questions

Q: What is Bun and what does it do?

Bun is a JavaScript, TypeScript, and CSS transpiler, minifier, and bundler, as well as an npm-compatible package manager and Jest-like test runner.

Q: Why was Bun initially written in Zig?

Bun was initially written in Zig because of its low-level control and care for performance, which allowed the project's creator to build a significant amount of functionality in a short amount of time.

Q: What are the challenges faced by the current Zig implementation of Bun?

The current Zig implementation of Bun has faced numerous challenges, including heap-use-after-free crashes, use-after-free crashes, and memory leaks, which have been addressed in recent versions.

Q: How may the acquisition of Bun by Anthropic influence the project's development and direction?

The acquisition of Bun by Anthropic may bring new resources and expertise to the project, potentially accelerating its development and adoption, and influencing its future direction and priorities.