Bun vs Node.js vs Deno: JavaScript Runtime Comparison 2026

The JavaScript runtime landscape has transformed dramatically. For years, Node.js was the only serious server-side option. Then Deno arrived in 2018 with security-first promises and built-in TypeScript. Then Bun exploded onto the scene — and benchmarks went wild.

In 2026, all three runtimes are mature, production-tested, and backed by real companies. The question is no longer “which one exists?” but “which one is right for your workload?” This guide cuts through the hype with real benchmarks, compatibility tables, and honest trade-off analysis.

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The Three Runtimes at a Glance

Feature	Node.js 22	Deno 2.x	Bun 1.x
Engine	V8	V8	JavaScriptCore
Created by	Ryan Dahl (OpenJS)	Ryan Dahl (Deno Land)	Jarred Sumner (Oven)
Language	C++	Rust	Zig
TypeScript	Via transpiler	Native (built-in)	Native (built-in)
npm compatible	Yes (native)	Yes (via npm: specifier)	Yes (full compatibility)
Package manager	npm/yarn/pnpm	deno add / jsr	Bun built-in
Web APIs	Partial	Extensive	Extensive
Stable since	2009	2020	2023
License	MIT	MIT	MIT

Each runtime makes fundamentally different bets about what matters most. Understanding those bets helps you pick the right tool instead of fighting abstractions.

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Startup Time Benchmarks

Startup latency matters most for serverless functions, CLI tools, and any scenario where processes start and stop frequently.

Cold Start Comparison

These results are representative benchmarks from the runtimes’ own test suites and community benchmarks (results vary by hardware):

Hello World script startup:
- Bun:    ~5ms
- Deno:   ~30ms
- Node:   ~50ms

HTTP server first-request latency:
- Bun:    ~10ms
- Deno:   ~45ms
- Node:   ~70ms

Bun’s use of JavaScriptCore (WebKit’s engine, not V8) gives it a significant startup advantage. JavaScriptCore was built for browsers where startup speed matters; V8 was optimized for long-running processes.

Takeaway: If you’re writing Lambda functions or CLI tools that spawn frequently, Bun’s startup advantage compounds quickly.

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HTTP Server Performance

Throughput comparison matters for long-running API servers. Here’s a simplified HTTP server in each runtime, plus performance notes:

Node.js HTTP Server

// server.js
const http = require('http');

const server = http.createServer((req, res) => {
  res.writeHead(200, { 'Content-Type': 'text/plain' });
  res.end('Hello from Node.js\n');
});

server.listen(3000, () => {
  console.log('Node.js server on :3000');
});

Run: node server.js

Node’s raw HTTP module is fast, but most production apps add Express or Fastify on top, which adds overhead. Node.js shines when workloads are I/O-bound — it’s been battle-tested on millions of production systems.

Deno HTTP Server

// server.ts
Deno.serve({ port: 3000 }, (req) => {
  return new Response('Hello from Deno\n', {
    headers: { 'Content-Type': 'text/plain' },
  });
});

console.log('Deno server on :3000');

Run: deno run --allow-net server.ts

Deno’s Deno.serve() API wraps the native HTTP/2-capable hyper server. The --allow-net flag is mandatory — Deno’s permission system prevents silent network access.

Bun HTTP Server

// server.ts
const server = Bun.serve({
  port: 3000,
  fetch(req) {
    return new Response('Hello from Bun\n', {
      headers: { 'Content-Type': 'text/plain' },
    });
  },
});

console.log(`Bun server on :${server.port}`);

Run: bun server.ts

No flag needed. Bun’s Bun.serve() uses a custom HTTP implementation that bypasses some Node.js compatibility overhead. Benchmarks consistently show Bun serving 2–3× more requests per second than Node for simple handlers.

Throughput Numbers (Approximate, wrk 10s benchmark)

Simple JSON API (req/sec):
- Bun:    ~250,000 req/s
- Deno:   ~130,000 req/s
- Node:   ~90,000 req/s (bare http)
- Node:   ~45,000 req/s (Express)
- Node:   ~75,000 req/s (Fastify)

Important caveat: Raw throughput rarely determines production performance. Database latency, business logic, and connection pooling dominate real-world benchmarks. Don’t choose a runtime purely on “hello world” numbers.

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Memory Usage

Memory footprint affects hosting costs and vertical scaling ceilings.

Idle process memory:
- Node.js:  ~30–50 MB
- Deno:     ~20–35 MB
- Bun:      ~15–25 MB

Under load (100 concurrent connections):
- Node.js:  ~80–120 MB
- Deno:     ~60–100 MB
- Bun:      ~45–80 MB

Bun and Deno both benefit from more modern memory management than Node.js’s C++ core. However, Node.js’s memory characteristics are extremely well-understood — there are years of production telemetry, profiling tools, and leak-detection strategies for it.

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TypeScript Support

This is where the runtimes diverge philosophically.

Node.js: TypeScript via External Tools

Node.js doesn’t run TypeScript natively. You need a compile step:

# Option 1: ts-node (development)
npx ts-node server.ts

# Option 2: tsc + node (production)
npx tsc && node dist/server.js

# Option 3: tsx (fast transpilation, no type checking)
npx tsx server.ts

# Option 4: Node 22+ --experimental-strip-types
node --experimental-strip-types server.ts

Node.js 22 introduced --experimental-strip-types which strips TypeScript syntax without type-checking — a middle ground. But for full type-checking, you still need tsc.

Verdict: Extra setup, but maximum ecosystem flexibility. Most Node.js TypeScript setups are mature and battle-tested.

Deno: TypeScript as First-Class Citizen

# Just run it — no config needed
deno run server.ts

# With type checking
deno check server.ts

Deno compiles TypeScript natively. No tsconfig.json required for basic usage (though you can provide one). The type-checker is integrated, not bolted on.

Verdict: Best TypeScript developer experience out of the box. Excellent for projects where you want strong types without a build step.

Bun: TypeScript via JavaScriptCore Transpilation

# Just run it
bun server.ts

# Type checking (Bun transpiles but doesn't type-check)
bun run tsc --noEmit

Bun transpiles TypeScript using its own transpiler (not tsc). This is fast — faster than ts-node — but Bun doesn’t type-check at runtime. You need to run tsc --noEmit separately for type safety.

Verdict: Fastest TypeScript execution, but be aware that runtime errors from type mistakes are possible if you skip tsc.

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npm Compatibility

npm compatibility is a practical dealbreaker for most teams.

Node.js: Full npm Compatibility (Native)

Node.js invented npm. Everything works. If a package exists on npm, it runs on Node.js.

npm install express
node -e "require('express')" # Works

Deno: npm via Specifiers

Deno 2.x added solid npm support:

// Use npm packages with npm: prefix
import express from "npm:express";
import { z } from "npm:zod";

// Or use deno.json to manage deps

// deno.json
{
  "imports": {
    "express": "npm:express@^4.18.0",
    "zod": "npm:zod@^3.22.0"
  }
}

About 95% of npm packages work in Deno 2.x. Exceptions include packages that rely on Node.js-specific internals (native addons, certain process APIs). The node: compatibility layer covers most standard modules.

Bun: Full npm Compatibility by Design

Bun was built to be a drop-in Node.js replacement:

bun install  # Reads package.json, installs deps
bun add express
bun run server.ts  # Works exactly like node

Bun installs packages 10–25× faster than npm because it downloads binary packages in parallel and stores them in a global cache. It’s compatible with package.json, lock files, and workspaces.

Compatibility edge cases: Some packages that use native Node.js C++ addons (.node files) may not work in Bun. This affects packages like sharp (image processing) and certain database drivers on older versions.

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Web API Support

Modern runtimes aim to align with browser Web APIs, enabling code sharing between client and server.

Web API	Node.js 22	Deno 2.x	Bun 1.x
fetch	✅ (stable)	✅	✅
Request / Response	✅	✅	✅
ReadableStream	✅	✅	✅
WebSocket (server)	✅ (via ws)	✅ (native)	✅ (native)
Crypto (Web Crypto)	✅	✅	✅
URL / URLSearchParams	✅	✅	✅
FormData	✅	✅	✅
AbortController	✅	✅	✅
TextEncoder/Decoder	✅	✅	✅
localStorage	❌	✅	❌

All three runtimes now support the WinterCG (Web-interoperable Runtimes Community Group) minimum API surface, which means code targeting WinterCG APIs is increasingly portable across runtimes.

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Security Model

This is Deno’s flagship differentiator.

Deno: Explicit Permissions

# Deny all by default — must grant explicit permissions
deno run --allow-net server.ts
deno run --allow-read=./data --allow-net=api.example.com scraper.ts
deno run --allow-all script.ts  # Full access (not recommended)

Deno requires explicit permission flags for:

• Network access (--allow-net)
• File system reads (--allow-read)
• File system writes (--allow-write)
• Environment variables (--allow-env)
• Running subprocesses (--allow-run)

This creates an audit trail and prevents dependency supply-chain attacks from silently exfiltrating data.

Node.js: Opt-in Permissions (Experimental)

Node.js 22 introduced an experimental --permission flag, but it’s not widely used:

node --experimental-permission --allow-fs-read=./data server.js

The default is still “full access,” meaning a compromised dependency can read your filesystem.

Bun: No Permission System

Bun scripts have full access by default. There’s no permission model. For untrusted code execution, you’d need OS-level sandboxing (containers, VMs).

Verdict: If you’re running third-party scripts or operating in security-sensitive environments, Deno’s permission model is a genuine advantage. For trusted internal code, it adds boilerplate without benefit.

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Ecosystem and Tooling

Bundled Tooling Comparison

Tool	Node.js	Deno	Bun
Package manager	npm (separate)	deno add / JSR	bun install (built-in)
Test runner	Jest/Vitest (separate)	deno test (built-in)	bun test (built-in)
Bundler	Webpack/esbuild (separate)	deno bundle (deprecated)	bun build (built-in)
Linter	ESLint (separate)	deno lint (built-in)	—
Formatter	Prettier (separate)	deno fmt (built-in)	—
Watch mode	nodemon (separate)	--watch (built-in)	--watch (built-in)

Bun and Deno both ship with batteries-included tooling. Node.js’s ecosystem is larger and more mature, but requires assembling your own tool chain.

Package Registry

• Node.js: npm (2+ million packages — the largest)
• Bun: npm (full compatibility)
• Deno: npm + JSR (JavaScript Registry) — Deno’s own modern registry

JSR is worth watching. It enforces TypeScript-first packages and automatic documentation generation. Some popular packages are publishing JSR-native versions.

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Real-World Use Cases

When to Choose Node.js

• Enterprise applications where stability and ecosystem maturity trump performance
• Large existing codebases already running on Node.js
• Teams with strong Node.js expertise who don’t want retraining costs
• Packages that require native addons (.node bindings, certain drivers)
• Any project where the specific npm package you need hasn’t been tested on Bun/Deno

Node.js has 15+ years of production battle-hardening. When in doubt, Node.js will work.

When to Choose Deno

• Security-sensitive workloads where dependency isolation matters (fintech, healthcare)
• TypeScript-first teams who want zero-config type safety
• Serverless functions where cold starts and attack surface matter
• Script automation where you want granular permission control
• Fresh projects where you can use modern standards (ES modules, Web APIs) throughout
• Teams that want built-in linting/formatting without configuring the tool chain

When to Choose Bun

• CLI tools where startup speed is the primary metric
• Test-heavy projects — Bun’s test runner is significantly faster than Jest
• Package management — bun install is dramatically faster than npm/yarn
• Existing Node.js projects wanting a drop-in performance upgrade
• Monorepos where install speed compounds across many packages
• Edge functions where lightweight footprint matters

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Migration Considerations

Moving from Node.js to Bun

Bun is designed as a drop-in replacement. Most migrations are:

# Replace npm with bun
npm install → bun install
npm run dev → bun run dev
node server.js → bun server.js

Watch out for: Native addons, __dirname/__filename in ESM (use import.meta.dirname instead), some obscure process.* APIs.

Moving from Node.js to Deno

More migration work required:

// Old (CommonJS)
const fs = require('fs');

// New (Deno)
import { readFile } from 'node:fs/promises';
// or use Deno's built-in APIs
const content = await Deno.readTextFile('./file.txt');

Permission flags must be added everywhere. Import paths need review. But Deno’s node: compatibility layer handles most standard library modules.

Running Bun in Production

Bun 1.x is production-ready. Discord, Vercel edge functions, and many startups run Bun in production. Container setup is straightforward:

FROM oven/bun:1 as base
WORKDIR /app
COPY package.json bun.lockb ./
RUN bun install --frozen-lockfile
COPY . .
EXPOSE 3000
CMD ["bun", "run", "start"]

Use the npm package size checker to audit dependencies before migrating to ensure compatibility.

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Performance Summary

The performance story in 2026 is nuanced:

Bun wins at:

• Startup time (3–10× faster than Node.js)
• Package install speed (10–25× faster)
• Raw HTTP throughput (2–3× faster simple handlers)
• Test execution speed (5–10× faster than Jest)

Node.js wins at:

• Ecosystem depth
• Production stability
• Tooling maturity
• Native addon support

Deno wins at:

• Security model
• TypeScript integration
• Web standards compliance
• Built-in tooling quality

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The Verdict: Which Runtime in 2026?

New greenfield project, TypeScript-first, small team?
→ Bun or Deno

Existing Node.js app, want faster tests and installs?
→ Bun (drop-in upgrade)

Security-sensitive or script automation?
→ Deno

Enterprise, large team, stability required?
→ Node.js

CLI tool where startup speed matters?
→ Bun

Serverless functions (Lambda, Cloudflare Workers)?
→ Bun or Deno (check platform support)

The honest answer: all three are excellent in 2026. The days of “just use Node.js by default” are over — Bun and Deno have earned serious consideration. But Node.js’s ecosystem moat is still wide. For most teams, the best strategy is to use Bun for tooling (package installs, test runner) even while running Node.js in production — you get the performance wins with zero risk.

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Tools to Help You Decide

Before committing to a runtime, audit your dependencies:

• npm Package Size Checker — see if your deps are Bun/Deno-compatible
• npm Package Compare — compare package stats before switching
• Package.json Validator — ensure your config is valid before migrating
• Semantic Version Bumper — manage version constraints during migration

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Further Reading

• Node.js 22 Release Notes
• Bun 1.x Documentation
• Deno 2.x Documentation
• WinterCG Specifications