Side by side

Node.jsvsBun

Q: Can I use Bun in an existing Node.js project?

Often, yes. Start with bun install or bun test while the app keeps running on Node.js, then try bun run once the tests pass, since a few packages may still behave differently.

What is the difference between Node.js and Bun?

Updated October 6, 20263 min read8 differences

In short

Node.js is the long-standing JavaScript runtime built on V8; Bun is a faster-starting runtime on JavaScriptCore that also installs, tests and bundles code.

Backend & APIsp. 35

Node.js

Node.js is an open-source JavaScript runtime that runs JavaScript outside the browser, most often to build web servers, APIs, and command-line tools.

Read the page on Node.js

Backend & APIsp. 9

Bun

Bun is a fast JavaScript and TypeScript runtime that is also a package manager, bundler and test runner, designed as a drop-in replacement for Node.js.

Read the page on Bun

Node.js and Bun compared

Aspect	Node.js	Bun
Engine and core	V8 (Chrome's engine), core in C++	JavaScriptCore (Safari's engine), core in Zig
Released	2009	Version 1.0 in 2023
Package manager	npm, installed alongside Node.js	`bun install`, built in and npm-compatible
TypeScript and JSX	Strips types from many `.ts` files; JSX needs a build tool	Runs both directly, with no configuration
Testing and bundling	`node --test` built in; bundling needs a separate tool	`bun test` (Jest-compatible) and `bun build` built in
Speed	The baseline for startup and installs	Faster startup; much faster installs
Compatibility	The reference that npm packages are written for	Implements most Node.js APIs; some packages behave differently
Governance	An OpenJS Foundation project	Owned by Anthropic since December 2025; MIT-licensed

The difference, explained

Node.js and Bun both run JavaScript and TypeScript outside the browser, on servers and developer machines. Node.js, released in 2009, is built on Chrome's V8 engine, ships with npm and is the runtime most packages, frameworks and hosts are built for. Bun, started by Jarred Sumner and stable since version 1.0 in 2023, uses JavaScriptCore, the engine behind Safari, is written in Zig and comes as a single bun executable that is also a package manager, test runner and bundler.

Bun is designed as a drop-in replacement: it implements Node.js built-in modules such as node:fs and node:http, reads package.json and node_modules and runs most npm packages unchanged. So the differences are speed and tooling. Bun starts faster, installs dependencies much faster with bun install, runs TypeScript and JSX directly, and includes a Jest-compatible test runner and a bundler; a Node.js project usually pairs the runtime with npm, a bundler such as Vite or esbuild and a test framework, although Node.js has added its own test runner and can strip types from many .ts files.

They also work together. Many teams adopt Bun piece by piece, using bun install or bun test in a Node.js project while production stays on Node.js, and try bun run once the tests pass. Bun's own APIs, such as Bun.serve and bun:sqlite, cover common jobs without extra packages but tie code to Bun. Node.js is governed by the OpenJS Foundation; Bun has been owned by Anthropic since December 2025 and remains open source under the MIT license.

A common misconception is that switching to Bun makes every app much faster. Its biggest gains are in startup, installs and tests; a typical web app spends much of its time waiting on databases and networks, so measure your own workload. Compatibility is also high but not complete: packages that depend on Node.js internals or native add-ons can behave differently, and Node.js has a far longer record in production.

Which one should you use?

Choose Node.js when…

You need the widest compatibility with npm packages, native add-ons and hosts.
A long production record matters more than install or startup speed.
Your team's npm, bundler and test setup already works well.

Choose Bun when…

Slow installs and test runs hold up daily work or CI.
You want TypeScript, testing and bundling from one tool with no configuration.
You are starting a new server or command-line tool and can check compatibility early.
Fast startup matters, as in scripts and short-lived processes.

The everyday toolchain in Node.js and Bun

Node.jsbash

# Node.js: the runtime, with npm and other tools beside it
npm install            # install dependencies (package-lock.json)
node server.ts         # run TypeScript by stripping types
node --test            # run tests with the built-in runner
npx cowsay "Hello"     # run a package's command once

# Bundling needs a separate tool, such as esbuild
npx esbuild src/index.ts --bundle --outdir=dist

Bunbash

# Bun: one executable for all of it
bun install            # install dependencies (bun.lock)
bun run server.ts      # run TypeScript or JSX directly
bun test               # run Jest-compatible tests
bunx cowsay "Hello"    # run a package's command once

# Bundling is built in
bun build src/index.ts --outdir dist

Readers ask

Is Bun faster than Node.js?

It usually starts faster and installs packages much faster. For a running web app the gap is smaller, since much of the time goes to databases and networks, so benchmark your own workload.

Can I use Bun in an existing Node.js project?

Often, yes. Start with bun install or bun test while the app keeps running on Node.js, then try bun run once the tests pass, since a few packages may still behave differently.

Is Bun ready for production?

Bun has had stable releases since version 1.0 in 2023, and many teams run it in production. Run your test suite on it first, because compatibility with every Node.js API and package is not guaranteed.