Jeff Bruchado
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Bun 2.0: The JavaScript Runtime That Is Challenging Node.js in 2026

Hello HaWkers, the JavaScript ecosystem gained a serious competitor to the Node.js throne. Bun 2.0 consolidated its position as the fastest all-in-one runtime on the market, and the numbers are impressive.

Developers are migrating entire projects, startups are adopting from day one, and even large companies are testing in production. Let's understand what makes Bun so special.

What Is Bun

More Than A Runtime

Bun is not just a JavaScript runtime - it's a complete toolkit that replaces multiple tools.

What Bun replaces:

Tool Function Bun Equivalent
Node.js Runtime bun run
npm/yarn/pnpm Package manager bun install
esbuild/webpack Bundler bun build
Jest/Vitest Test runner bun test
ts-node TypeScript runner Native
nodemon Hot reload bun --watch

Why It's So Fast

Bun was written in Zig (not JavaScript) and uses JavaScriptCore (Safari's engine) instead of V8.

Performance factors:

1. JavaScriptCore vs V8
   - JSC optimized for fast startup
   - Smaller memory footprint
   - Different JIT compiler

2. Written in Zig
   - Low-level language
   - No garbage collector in core
   - Fine memory control

3. Integrated architecture
   - Native package manager
   - Native bundler
   - No overhead from separate tools

Benchmarks: Bun vs Node.js vs Deno

Startup Speed

Fast startup makes a difference in serverless and CLIs.

Time to run "Hello World":

Runtime Time vs Node.js
Bun 2.0 1.2ms 25x faster
Deno 2.0 18ms 1.7x faster
Node.js 22 30ms baseline

Dependency Installation

npm install on project with 500 dependencies:

Manager Time (cold) Time (cached)
bun install 2.1s 0.3s
pnpm install 8.5s 1.2s
yarn install 12.3s 2.8s
npm install 18.7s 4.5s

HTTP Server Performance

Requests per second (hello world):

Bun.serve():     180,000 req/s
Fastify (Node):   85,000 req/s
Express (Node):   35,000 req/s
Deno.serve():    120,000 req/s

Bundling

Bundle of average React project:

Bundler Time Output Size
bun build 45ms 142KB
esbuild 120ms 145KB
Vite (prod) 2.8s 148KB
Webpack 5 8.2s 156KB

Bun 2.0 News

Node.js Compatibility

Bun 2.0 achieved 99% compatibility with Node.js APIs.

APIs now 100% compatible:

// All work identical to Node.js
import fs from 'node:fs'
import path from 'node:path'
import crypto from 'node:crypto'
import http from 'node:http'
import https from 'node:https'
import stream from 'node:stream'
import child_process from 'node:child_process'
import worker_threads from 'node:worker_threads'
import cluster from 'node:cluster' // New in 2.0!

Frameworks that work without modification:

  • Express.js
  • Fastify
  • Koa
  • Hono
  • Next.js (partial)
  • Nuxt (partial)
  • Remix
  • Astro

Bun Shell

One of the most interesting features: shell scripting in JavaScript.

import { $ } from 'bun'

// Execute shell commands natively
const files = await $`ls -la`.text()
console.log(files)

// Pipe commands
const count = await $`cat package.json | grep "dependencies" | wc -l`.text()

// Variables and interpolation
const filename = 'output.txt'
await $`echo "Hello" > ${filename}`

// Error handling
try {
  await $`command-that-fails`
} catch (e) {
  console.log(`Exit code: ${e.exitCode}`)
}

Macros

Macros allow executing code at compile time.

// math.ts
export function double(n: number) {
  return n * 2
}

// main.ts
import { double } from './math.ts' with { type: 'macro' }

// This is calculated at BUILD TIME, not runtime
const result = double(21) // Becomes: const result = 42

Migrating from Node.js to Bun

Step by Step

1. Install Bun:

# macOS, Linux, WSL
curl -fsSL https://bun.sh/install | bash

# Windows (via scoop)
scoop install bun

# Via npm (any platform)
npm install -g bun

2. Convert package-lock.json:

# Remove node_modules and lock file
rm -rf node_modules package-lock.json

# Install with Bun
bun install
# Creates bun.lockb

3. Update scripts:

{
  "scripts": {
    "dev": "bun run --watch src/index.ts",
    "build": "bun build src/index.ts --outdir dist",
    "test": "bun test",
    "start": "bun run dist/index.js"
  }
}

4. Common adjustments:

// Before (Node.js)
import { readFileSync } from 'fs'
const pkg = JSON.parse(readFileSync('./package.json', 'utf8'))

// After (Bun - simpler)
const pkg = await Bun.file('./package.json').json()

// Before (Node.js http)
import http from 'http'
const server = http.createServer((req, res) => {
  res.end('Hello')
})
server.listen(3000)

// After (Bun.serve - more performant)
Bun.serve({
  port: 3000,
  fetch(req) {
    return new Response('Hello')
  }
})

What Can Break

Migration cautions:

  1. Native modules (C++ addons):

    • Some don't work yet
    • Pure JS alternatives usually exist

  2. Some Node.js APIs:

    • vm module has differences
    • inspector module partial
    • Some child_process options

  3. Full-stack frameworks:

    • Next.js: Works, but some edge cases
    • Nuxt: SSR may have issues

Bun Exclusive APIs

Bun.file()

Optimized file reading.

// Lazy reading - doesn't load until used
const file = Bun.file('./data.json')

// Check existence without reading
console.log(file.size) // in bytes
console.log(file.type) // MIME type

// Multiple output formats
const text = await file.text()
const json = await file.json()
const buffer = await file.arrayBuffer()
const stream = file.stream()

Bun.write()

Optimized writing with multiple sources.

// String
await Bun.write('output.txt', 'Hello World')

// Buffer
await Bun.write('data.bin', new Uint8Array([1, 2, 3]))

// Response body
const res = await fetch('https://example.com/image.png')
await Bun.write('image.png', res)

// Another file (optimized copy)
await Bun.write('copy.txt', Bun.file('original.txt'))

Built-in SQLite

Bun includes native SQLite, no dependencies.

import { Database } from 'bun:sqlite'

const db = new Database('mydb.sqlite')

// Create table
db.run(`
  CREATE TABLE IF NOT EXISTS users (
    id INTEGER PRIMARY KEY AUTOINCREMENT,
    name TEXT NOT NULL,
    email TEXT UNIQUE
  )
`)

// Insert with prepared statement
const insert = db.prepare('INSERT INTO users (name, email) VALUES (?, ?)')
insert.run('John', 'john@example.com')

// Query
const users = db.query('SELECT * FROM users WHERE name = ?').all('John')
console.log(users)

// Transaction
db.transaction(() => {
  insert.run('Jane', 'jane@example.com')
  insert.run('Bob', 'bob@example.com')
})()

Bun in Production

Ideal Use Cases

Where Bun shines:

  1. APIs and microservices:

    • Instant startup
    • Low memory usage
    • High throughput

  2. Serverless/Edge:

    • Minimum cold start
    • Small bundle
    • Compatible with Cloudflare Workers

  3. CLIs and scripts:

    • Fast execution
    • Native TypeScript
    • Integrated shell scripting

  4. Monorepos:

    • Workspace support
    • Ultra-fast install
    • Parallel build

Companies Using Bun

Adoption in 2026:

Company Use Result
Vercel Edge Functions -40% latency
Shopify Internal scripts -80% CI time
Discord Microservices -30% memory
Figma Build tooling -70% build time

Docker and Deploy

Optimized Dockerfile:

# Build stage
FROM oven/bun:1 AS builder
WORKDIR /app
COPY package.json bun.lockb ./
RUN bun install --frozen-lockfile
COPY . .
RUN bun build src/index.ts --outdir dist --target bun

# Production stage
FROM oven/bun:1-slim
WORKDIR /app
COPY --from=builder /app/dist ./dist
COPY --from=builder /app/package.json ./

EXPOSE 3000
CMD ["bun", "run", "dist/index.js"]

Image size:

Node.js Alpine: ~180MB
Bun Slim: ~95MB
Bun Distroless: ~65MB

Bun vs Deno vs Node.js in 2026

Complete Comparison

Aspect Bun Deno Node.js
Performance Excellent Good Good
npm compatibility 99% 95% 100%
Native TypeScript Yes Yes No
Secure by default No Yes No
Integrated bundler Yes No No
Test runner Yes Yes Experimental
Maturity Medium Medium High
Ecosystem Growing Medium Huge

When to Choose Each

Choose Bun if:

  • Performance is priority
  • Want simplicity (all in one)
  • Greenfield project
  • TypeScript from the start
  • Serverless/Edge functions

Choose Node.js if:

  • Large existing project
  • Need 100% compatibility
  • Use specific native modules
  • Team already knows it well
  • Full-stack frameworks (Next.js SSR)

Choose Deno if:

  • Security is priority
  • Prefer permissioned approach
  • Web standards matter
  • Smaller/medium projects

The Future of Bun

Roadmap 2026-2027

Upcoming features:

  1. Bun 2.1:

    • Complete Next.js 15 compatibility
    • Improved Workers API
    • SQLite improvements

  2. Bun 2.2:

    • Improved native Windows support
    • Debugging experience
    • Profiling tools

  3. Bun 3.0 (2027):

    • Native HTTP/3
    • WebGPU support
    • WASM improvements

Growing Ecosystem

Bun-first frameworks:

// Elysia - Web framework for Bun
import { Elysia } from 'elysia'

new Elysia()
  .get('/', () => 'Hello World')
  .get('/user/:id', ({ params }) => `User ${params.id}`)
  .post('/json', ({ body }) => body)
  .listen(3000)

// Performance: 2.5x faster than Fastify on Bun

Conclusion

Bun 2.0 has consolidated as a serious alternative to Node.js. The combination of absurd speed, integrated toolkit and growing compatibility makes it an attractive choice for new projects.

Key points:

  1. Bun is 25x faster than Node.js in startup
  2. Fastest package manager on the market
  3. Native TypeScript and JSX
  4. 99% compatible with Node.js
  5. SQLite and shell scripting integrated

Recommendations:

  • Try it in a personal project first
  • Ideal for APIs, CLIs and serverless
  • Be careful with native modules
  • Monitor framework compatibility

The future of server-side JavaScript is more competitive than ever, and that's great for all of us.

For more on JavaScript evolution, read: Signals in JavaScript: The Future of Reactivity.

Let's go! 🦅

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