Bun (software)

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Bun
Original authorJarred Sumner
DeveloperAnthropic
Initial releaseSeptember 14, 2021; 4 years ago (2021-09-14)[1]
Stable release
1.3.5[2] Edit this on Wikidata / 17 December 2025; 7 days ago (17 December 2025)
Repositorygithub.com/oven-sh/bun
Written inZig, C++ (JSC bindings), C (WebSocket bindings), TypeScript, JavaScript
Operating systemLinux, macOS, Windows
TypeRuntime environment
LicenseMIT license[3]
Websitebun.com

Bun is a JavaScript runtime, package manager and test runner designed as a drop-in replacement for Node.js.[4][5] Bun uses Safari's JavaScriptCore as its JavaScript engine ,[6] unlike Node.js and Deno, which run on the V8 engine used by the Chromium project. It is currently owned by Anthropic PBC, having formerly been its own company, Oven.

Overview

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Bun supports bundling, minifying, server-side rendering (Svelte, Nuxt.js, Vite). Bundling refers to the process of combining multiple files and assets like JavaScript, CSS, and HTML files into a smaller number of files, to reduce the number of server requests and enhance performance.[7] Minifying is a technique of compressing files by removing unnecessary characters (like whitespace, comments, etc.) without affecting their functionality, further optimizing website load times. Bun provides an API to decide whether to preserve some readability by e.g. keeping whitespace.[7]

The runtime supports foreign function interface (FFI), SQLite3, TLS 1.3, and DNS resolution. It also comes bundled in with common tools like file editing, HTTP servers, WebSocket, and hashing.[8]

History

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The first stable release of Bun, 1.0, was released on September 8, 2023.[9]

Bun 1.1 added support for Windows 10 and Windows 11.[10][11] It also introduced a cross-platform Bun Shell for running some Bash commands without extra dependencies.[10][11]

With version 1.3, Bun added hot module replacement (HMR) to its local development server, which updates pages as code changes automatically.[12]

On December 2, 2025, Bun announced that the project has been acquired by Anthropic. This acquisition allows the company to use Bun to support Claude Code and the Claude Agent SDK.[13]

Funding

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On August 24, 2022, Oven, the company behind Bun, announced it had raised $7 million in funding. The round was led by Kleiner Perkins, with participation from Guillermo Rauch, Y Combinator, and others.[14]

Acquisition

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On December 2, 2025, Jarred Sumner, creator of Bun, announced that Bun is joining Anthropic on a blog post. He put emphasis on the fact that Bun will stay open-sourced and under the MIT License, and mentioned that the funding will allow them to hire more engineers, dramatically speeding up the development cycle and helping to release new feature updates quicker. Additionally, it is said that they will help make tools like Claude Code and Claude Agent SDK, which are owned by Anthropic.[13] The cost of this acquisition has not been publicly disclosed.

References

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  1. ^ "Releases, oven-sh/bun, Github". GitHub. Retrieved 14 September 2021.
  2. ^ "Release 1.3.5". 17 December 2025. Retrieved 19 December 2025.
  3. ^ Sumner, Jarred (2023-07-02). "License". Bun Docs. Archived from the original on 2023-07-06. Retrieved 2023-07-07.
  4. ^ "What is Bun? | Bun Docs". Bun. Archived from the original on 2023-12-11. Retrieved 2024-04-01.
  5. ^ Tyson, Matthew (February 23, 2023). "Explore Bun.js: The all-in-one JavaScript runtime". InfoWorld. Archived from the original on October 4, 2023. Retrieved October 11, 2023.
  6. ^ Omolana, Timilehin (2022-08-02). "What Is Bun.js and Why Is the JavaScript Community Excited About It?". makeuseof.com. Archived from the original on 2023-05-30. Retrieved 2023-05-30.
  7. ^ a b "The Bun Bundler". Bun. 2023-05-16. Archived from the original on 2024-04-03. Retrieved 2024-04-03.
  8. ^ "Bun APIs". Bun Docs. Archived from the original on September 27, 2023. Retrieved September 11, 2023.
  9. ^ "Bun 1.0". bun.sh. Archived from the original on 2024-04-30. Retrieved 2024-04-30.
  10. ^ a b "Bun 1.1". Bun. 2024-04-01. Archived from the original on 2024-06-07. Retrieved 2024-04-03.
  11. ^ a b Anderson, Tim (2024-04-02). "Bun 1.1 released with Windows support, stable WebSocket client and more • DEVCLASS". DEVCLASS. Archived from the original on 2024-04-03. Retrieved 2024-04-03.
  12. ^ "Bun 1.3". Bun. 2025-10-10. Retrieved 2025-11-07.
  13. ^ a b "Bun is joining Anthropic". Bun. 2025-12-02. Retrieved 2025-12-02.
  14. ^ Bun [@bunjavascript] (2022-08-24). "Introducing Oven: the company behind Bun. Oven has raised $7m led by @buckymoore at Kleiner Perkins with participation from @rauchg @ycombinator and more https://t.co/HG2TUCQWbL" (Tweet) – via Twitter.
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