Bun v0.6.12

Jarred Sumner · June 30, 2023

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We've been releasing a lot of changes to Bun recently, here's a recap in case you missed it:

  • v0.6.0 - Introducing bun build, Bun's new JavaScript bundler.
  • v0.6.2 - Performance boosts: 20% faster JSON.parse, up to 2x faster Proxy and arguments.
  • v0.6.3 - Implemented node:vm, lots of fixes to node:http and node:tls.
  • v0.6.4 - Implemented require.cache, process.env.TZ, and 80% faster bun test.
  • v0.6.5 - Native support for CommonJS modules (previously, Bun did CJS to ESM transpilation),
  • v0.6.6 - bun test improvements, including Github Actions support, test.only(), test.if(), describe.skip(), and 15+ more expect() matchers; also streaming file uploads using fetch().
  • v0.6.7 - Node.js compatibility improvements to unblock Discord.js, Prisma, and Puppeteer
  • v0.6.8 - Introduced Bun.password, mocking in bun test, and toMatchObject()
  • v0.6.9 - Less memory usage and support for non-ascii filenames
  • v0.6.10 - fs.watch(), bun install bug fixes, bun test features, and improved CommonJS support
  • v0.6.11 - address a release build issue from v0.6.10

This release makes it easier to read runtime errors, improves Node.js compatiblity, adds await Bun.file(path).exists(), fixes bundler bugs and slightly reduces minifier output size.

To install Bun:

curl -fsSL https://bun.sh/install | bash
npm install -g bun
brew tap oven-sh/bun
brew install bun
docker pull oven/bun
docker run --rm --init --ulimit memlock=-1:-1 oven/bun

To upgrade Bun:

bun upgrade

Better runtime errors

We've made several improvements to runtime errors in Bun:

  • Patched JavaScriptCore to allow Bun to print Error.prototype.stack in the same style as V8.
  • Stack traces show fewer internal builtin functions
  • console.error(error) now includes indirect function names, such as let foo = function() {} will now show foo instead of anonymous
  • Error.captureStackTrace(err)'s err.stack property is no longer marked as read-only (this was incorrect)
  • Error.prototype.stack is now automatically sourcemapped.

Bun transpiles every file in the runtime. Before this release, error.stack would show the stack for the transpiled source, which was not very useful. Now, error.stack shows the stack for the original source, following an internal sourcemap generated for each file.

The output of console.log(error.stack) after:

Error: hello!
    at hey (error.js:1:29)
    at module code (error.js:4:16)

The output of console.log(error.stack) before:

module code@error.js:4:16
evaluate@[native code]
moduleEvaluation@[native code]
moduleEvaluation@[native code]
@[native code]
asyncFunctionResume@[native code]
promiseReactionJobWithoutPromise@[native code]
promiseReactionJob@[native code]


function hey() {
  return new Error("hello!").stack;

Improvements to CommonJS <> ES Module interop

When using require to load an ES Module at runtime, Bun now inserts the __esModule annotation which many npm packages transpiled with Babel need in order to work correctly. This fixed a bug with using @mui/styled-engine with bun test.

package.json "module" field is no longer used in Bun's runtime

Bundlers use the "module" field in package.json with a higher priority over the "main" field when bundling ES Modules, but Node.js does not use the "module" field at all.

Previously, Bun used the "module" at runtime (when package.json "exports" wasn't in use) similar to how bundlers use it, but this caused some packages to load the browser version of their code in Bun and Node.js versions in Node.

Bun's bundler continues to support the "module" field when building for browsers, but to improve Node.js compatibility, Bun's runtime no longer uses the "module" field.

SQLite3 Full-text search is enabled


Bun.file(path).exists() is a new method that returns a boolean indicating whether a file exists at the given path.

import { file, write } from "bun";

console.log(await file("hello.txt").exists()); // false
await write("hello.txt", "hello world");
console.log(await file("hello.txt").exists()); // true

Node.js compatibility improvements

Several bugfixes to node:http and node:stream have landed

Google Maps works

The @googlemaps/google-maps-services-js package now works in Bun, thanks to @dylan-conway fixing a bug in our node:http implmenetation where properties were marked as read only that shouldn't have been marked as read-only.

import { Client } from "@googlemaps/google-maps-services-js";

const client = new Client({});

    params: {
      locations: [{ lat: 45, lng: -110 }],
      key: "asdf",
    timeout: 1000, // milliseconds
  .then((r) => {
  .catch((e) => {

ytdl-core now works

The ytdl-core package now works in Bun, thanks to @paperdave fixing a couple bugs in our node:http and node:stream implementations:

import { createWriteStream } from "fs";
import ytdl from "ytdl-core";


Minifier improvements

Bun's minifier now minifies obj["a"] into obj.a and obj["a"] = 1 into obj.a = 1.


bun build --minify ./input.js`


const obj = {};
obj["a"] = 1;


const obj = {};
obj.a = 1;


const obj = {};
obj["a"] = 1;

This yields a 0.02% reduction in bundle size for vue and potentially a little faster at runtime (engines implement computed property accesses differently than regular property accesses).

Bundler bugfixes

A bug where two consecutive files that re-export another file using CommonJS module.exports = require() would produce invalid code has been fixed

// a.js
module.exports = require("./b");

// b.js
module.exports = require("./c");

// c.js
module.exports = {};
  • In certain cases, Bun's CommonJS -> ES Module transform in the bundler would inject exports.foo = undefined and that caused some packages which used Object prototype methods to throw an error and it bloated the code. This has been fixed.

More bugfixes

  • A regression breaking macros has been fixed
  • The resolve6 export in dns/promises was missing
  • The errorMonitor export in node:events was missing


See the changelog on GitHub