This is the biggest release of Bun yet.

Bun now has a built-in JavaScript and TypeScript bundler and minifier. Use it to bundle frontend apps or bundle your code into a standalone executable.

We've also been busy improving performance and fixing bugs as-per usual: writeFile() gets up to 20% faster on Linux, lots of bug fixes to Node.js compatiblity and Web API compatiblity, support for TypeScript 5.0 syntax, and various fixes to bun install.

Bun's new JavaScript bundler & minifier

The focus of this release is Bun's new JavaScript bundler, but the bundler is just the beginning of a larger project. In the next couple months, we'll be announcing Bun.App — a "super-API" that stitches together Bun's native-speed bundler, HTTP server, and file system router into a cohesive whole.

It can be used using the bun build CLI command or the new Bun.build() JavaScript API.

Bun.build({
 entrypoints: ["./src/index.tsx"],
 outdir: "./build",
 minify: true,
 // ...
});

bun build ./src/index.tsx --outdir ./build --minify

To learn more, check out our blog post introducing the Bun bundler.

Standalone executables

You can now create standalone executables with bun build.

bun build --compile ./foo.ts

This lets you distribute your app as a single executable file, without requiring users to install Bun.

You can also minify it to improve startup performance for large apps:

bun build --minify --compile ./three.ts
 [32ms] minify -123 KB (estimate)
 [50ms] bundle 456 modules
 [107ms] compile three

This is powered by Bun's new JavaScript bundler and minifier.

import.meta.main

You can now use import.meta.main to check if the current file is the entry point that started bun. This is useful for CLIs to determine if the current file is what started the app.

For example, if you have a file called index.ts:

console.log(import.meta.main);

And you run it:

But if you import it:

And run it:

Improvements to bun test

• bun test now reports time taken to run tests

• describe.skip has been implemented (thanks to _yogr)

• expect().toBeEven() and expect().toBeOdd() has been implemented (thanks to will-richards-ii)

Faster fs.writeFile on Linux

Transpiler improvements

This release also introduces many improvements to the transpiler. Here are some of the highlights:

• Parser support for TypeScript 5.0.
• Parser support for import attributes.
• Some npm packages threw "ReferenceError: Cannot access uninitialized variable" errors on import due to a bug with cyclical imports in Bun's transpiler. This has been fixed.
• Support for // @jsx, // @jsxImportSource, and // @jsxFragment comments.
• Dead code elimination for unused global constructor function calls like new Set().
• String template literal concatenation like foo${1}${"2"}${'3'} -> foo123.
• Parser bugfixes for the deprecated ES5 with statement.

A big thanks to @kzc for many helpful bug reports.

Node.js compatibility

• tls.Server has basic support (previously, not implemented)
• fs.promises.constants is now exported correctly (previously, it was missing)
• node:http's server module now (correctly) accepts a callback argument
• Timer.refresh() now works as expected
• Fixed mkdtemp and mkdtempSync errors

Web API compatibility

• new Request("http://example.com", otherRequest).url would previously return the url of otherRequest instead of "http://example.com". This has been fixed.
• Bun.file(path).lastModified has been added, which is similar to the File API's lastModified property
• Supported redirect: "error" in fetch()
• Fixed fetch.bind, fetch.call, and fetch.apply not working

Changelog

Contributors

And finally, thank you to all the contributors from the community that helped improve Bun this release: @privatenumber, @Lawlzer, @jakeboone02, @zhongweiy, @xHyroM, @rmorey, @marktani, @Kruithne, @will-richards-ii, @simon04, @alexlamsl, @flakey5, @MaanuVazquez, @Plecra, @silversquirl, @beeburrt, @aquapi, @blackmann