Bun v0.7.2

Jarred Sumner · August 3, 2023

Bun v0.7.2 adds support for node:worker_threads, node:diagnostics_channel, BroadcastChannel, improves compatibility with Node.js, and fixes a couple nasty memory leaks.

We're hiring C/C++ and Zig engineers to build the future of JavaScript! Join our team →

Bun is an incredibly fast JavaScript runtime, bundler, transpiler, and package manager — all in one. Over the past couple months, we've been releasing a lot of changes to Bun recently, here's a recap in case you missed it:

  • v0.6.12 - Sourcemap support in Error.stack, Bun.file().exists(), and Node.js bug fixes.
  • v0.6.13 - Implemented mock Date, faster base64 encoding, and fixes for WebSocket and node:tls.
  • v0.6.14 - process.memoryUsage(), process.cpuUsage(), process.on('beforeExit', cb), process.on('exit', cb) and crash fixes
  • v0.7.0 - Web Workers, --smol, structuredClone(), WebSocket reliability improvements, node:tls fixes, and more.
  • v0.7.1 - ES Modules load 30% - 250% faster, fs.watch fixes, and lots of node:fs compatibility improvements.

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

Node.js worker_threads

You can now use the node:worker_threads module in Bun. Worker remains a global variable, but you can now use packages & frameworks that depend on node:worker_threads in Bun.

import { Worker } from "node:worker_threads";

const worker = new Worker("./worker.js");

bun . - run the main file

You can now run a project in Bun with bun . when you don't want to type out a path to a file. It is equivalent to doing import '.'

bun .


The BroadcastChannel API is now available in Bun. It allows you to publish-subscribe to messages across multiple Worker threads and the main thread. This is a new global variable, so you can use it without importing anything just like in web browsers.

const channel = new BroadcastChannel("my-channel");
const message = { hello: "world" };

channel.onmessage = (event) => {
  console.log(event.data); // { hello: "world" }

Thanks to @dylan-conway for getting this working in Bun and the WebKit/Safari team for the original implementation.

postMessage() now supports Error

You can now use postMessage and structuredClone() to clone Error objects.

const error = new Error("hello world");
const clone = structuredClone(error);
console.log(clone.message); // "hello world"

Node.js node:diagnostics_channel support

You can now use the node:diagnostics_channel module in Bun. The node:diagnostics_channel module provides an API to create named channels to report arbitrary message data for diagnostics purposes.

Creating new TypedArray gets up to 40x faster

Module resolution change: browser and module exports conditions

Bun no longer respects the "browser" or "module" package.json "exports" conditions. This addresses bugs impacting Astro CLI, axios, and more.

  • Bun is not a web browser, so Bun should not use the "browser" package.json exports condition.
  • The "module" exports condition is used by older versions of tslib and that breaks packages which rely on tslib. We still support this in bun build, but not at runtime.

The list of package.json "exports" conditions Bun respects at runtime is now as follows:

  • "bun"
  • "worker"
  • "node"
  • "default"

When coming from an ES module, "import" is used and when coming from a CommonJS module, "require" is used as well.

This is technically a breaking change, but it will usually be more of a "fixing" change.

2 memory leaks fixed

A memory leak in strong references held by native code in Bun has been fixed. This is a leak of about 16 bytes, however it quickly adds up in long-running processes.

A memory leak in response.clone() has been fixed. The headers object was cloned twice.


We also fixed some bugs

PrintingErrorWriteFailed bug fixed

A regression from the async transpiler changes caused some imports to fail with PrintingErrorWriteFailed. This has been fixed.

file loader bug fix

A regression from the async transpiler changes caused file loader imports to fail to load unless explicitly passed via --loader. This has been fixed.

require('node:module') is now a Module constructor

require('node:module') is now a Module constructor, as it is in Node.js.

bun install --production with workspaces

A bug causing packages to not be updated in the lockfile when --production was used in a workspace has been fixed.

node:http file upload bug has been fixed

A bug where binary file uploads via node:http would produce incorrectly-encoded data has been fixed by @Hanaasagi. Thanks @Hanaasagi!

Internals changes

We migrated our JavaScript builtins from ES modules to CommonJS, which improves start time for "crypto" by about 30% and fixed a crash when importing "astro".


View the complete changelog