Bun v0.6.14

Ashcon Partovi · July 12, 2023

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As a reminder: Bun is an incredibly fast JavaScript runtime, bundler, transpiler, and package manager — all in one.

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 - Addressed a release build issue from v0.6.10.
  • 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.

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 support for process

Bun has improved support for the Node.js process object.

Memory usage

You can now use process.memoryUsage() to get the memory usage of Bun's process.

// {
//  rss: 4935680,
//  heapTotal: 1826816,
//  heapUsed: 650472,
//  external: 49879,
//  arrayBuffers: 9386
// }

CPU usage

You can also get the current CPU usage from Bun using process.cpuUsage().

// {
//  user: 38579,
//  system: 6986
// }

Signal events

You can now use process.on() to listen and run code when the process receives a signal event.

process.on("SIGINT", () => {
  console.log("Interrupt from keyboard");

Exit events

If you don't know which signal to listen for, you can also listen for a generic exit or beforeExit event.

process.on("beforeExit", (code) => {
  console.log("Event loop is empty and no work is left to schedule.", code);

process.on("exit", (code) => {
  console.log("Exiting with code:", code);


You can now use process.kill(pid, signal), which kills a process by pid.

process.kill(123, "SIGTERM");

getuid, geteuid, getgid, getegid, getgroups

The following methods have been added:

  • process.getegid()
  • process.geteuid()
  • process.getgid()
  • process.getgroups()
  • process.getuid()


process.assert() is a deprecated alternative to require("assert"). Bun adds this deprecated function for compatibility with existing npm packages.

process.assert(false, "PleAsE don't Use THIs It IS dEpReCATED");


process.reallyExit() is used by some npm packages to exit without triggering the "exit" event handler. This is an undocumented function which Bun now implements for ecosystem compatibility reasons.

process.reallyExit(); // probably just use process.exit() though

Class constructors in console.log

Previously, when a value was printed to console.log, a class would was mis-categorized as a function. This has now been fixed and shows that the value is a class.

console.log(class A {});
// Previous: [Function: A]
// Now: [class A]

Fixed TypeScript decorator bug

Previously, Bun had a bug where decorators were not evaluated when used on an anonymous default export. This has been fixed.

function decorator(target: unknown, propertyKey: unknown) {
  // ...

export default class {
  method() {
    // ...

Fixed fetch in URLs without slash

Previously, Bun would throw an error when a URL used in fetch() did not have a slash. This has been fixed.

await fetch("http://example.com?a=b");
// Previous: <throw>
// Now: Response { ... }

Fixed 2 crashes in Error.captureStackTrace

We've added a small stress test for Error.captureStackTrace and that led to fixing two crashes:

  • When the sourceURL of a stack frame was empty and Error.captureStackTrace() was called, incorrectly initialized memory could sometimes be passed to the stack trace sourcemapper. This has been fixed.
  • Creating the array of CallSite objects could sometimes cause a crash due to creating an Array using the fast path which prohbits additional GC-owned memory allocations until the Array has been fully initialized. Since the CallSite objects are each a GC-owned allocation, this could cause a crash when GC happens while creating these (suhc as when called repeatedly in a loop). This has been fixed.

Implemented throwIfNoEntry

Implemented support for the throwIfNoEntry option for stat and lstat in node:fs. If set to false and the file does not exist, it will return undefined instead of throwing an error.

import { statSync } from "node:fs";

statSync("./does-not-exist.txt"); // <throws>
statSync("./does-not-exist.txt", { throwIfNoEntry: false }); // undefined

Other changes

  • Implemented getCurves() in node:crypto

  • Added support for obscure HTTP methods.

  • Fixed a bug that caused bun build to non-deterministically rename symbols.

  • Fixed an off-by-one error that could cause stack traces show the wrong preview.

  • Fixed a bug where the readable event was being emitted after a stream was destroyed.

  • Fixed a bug where digest("binary") was not implemented properly.

  • Fixed bad coercion from large numbers and BigInt in node:fs.

  • Fixed the connection event from being emitted when it shouldn't.

  • Fixed a bug in HTMLRewriter where element.attributes used the wrong encoding.

  • Fixed a bug where the JIT from Buffer.isBuffer() would become invalid.

  • Fixed a regression for React support where the bundle size was larger than in previous releases.

  • Fixed a bug where ref() and unref() did not return the Timer object.

  • Fixed a bug where the metadata bits from randomUUID() were incorrect.

  • Fixed a crash from invalid utf-8 data in node:string_decoder.

  • Fixed a bug where Set-Cookie was not present in express-session because of a monkey-patch. (Thanks to @Hanaasagi for fixing those last three bugs!)


See the changelog on GitHub