Bun vs Node vs Deno: Picking Your JS Runtime

For 15 years, Node.js was the only game in town for server-side JavaScript. Now we have choices: Deno (from Node's original creator) and Bun (the new kid focused on speed).

I've built projects with all three. Here's my honest comparison.

The Quick Summary

Node.js: The incumbent. Massive ecosystem, proven at scale, slower than alternatives but battle-tested.

Deno: Security-first, TypeScript-native, modern APIs. More opinionated, smaller ecosystem.

Bun: Speed-obsessed. Fastest runtime, built-in bundler/test runner/package manager. Newest, still maturing.

Node.js: The Incumbent

Node has been around since 2009. It's what JavaScript servers run on. Every major company uses it.

Strengths:

• Ecosystem: 2+ million npm packages
• Stability: Production-proven at any scale
• Documentation: Every problem has a Stack Overflow answer
• Tooling: Excellent debugger, profiler, diagnostics

Weaknesses:

• Performance: Slower than Bun/Deno for many operations
• Legacy baggage: CommonJS, callback patterns, old APIs
• Security: No permission system (any code can do anything)
• Tooling fragmentation: Need separate tools for everything

When to use: Production applications, enterprise environments, when ecosystem compatibility matters most, when you need stability over speed.

// Node.js - the familiar
const http = require('http');
const fs = require('fs/promises');

const server = http.createServer(async (req, res) => {
  const data = await fs.readFile('./data.json', 'utf8');
  res.setHeader('Content-Type', 'application/json');
  res.end(data);
});

server.listen(3000);

Deno: The Rethink

Deno is Node's creator (Ryan Dahl) asking "what if I did it again, knowing what I know now?"

Strengths:

• Security by default: Explicit permissions for file/network/env access
• TypeScript native: No setup, just works
• Modern APIs: Web standard APIs (fetch, WebSocket, etc.)
• All-in-one: Built-in formatter, linter, test runner
• URL imports: Import directly from URLs

Weaknesses:

• Smaller ecosystem: Not all npm packages work
• Learning curve: Different patterns than Node
• Adoption: Less hiring demand, fewer tutorials
• npm compatibility: Better than before, still not 100%

When to use: New projects prioritizing security, TypeScript-first workflows, when you want modern DX without tool configuration.

// Deno - secure by default, TypeScript native
const server = Deno.serve({ port: 3000 }, async (req) => {
  const data = await Deno.readTextFile('./data.json');
  return new Response(data, {
    headers: { 'Content-Type': 'application/json' },
  });
});

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

Those flags are security permissions. Without --allow-net, the server can't listen. Without --allow-read, it can't read files.

Bun: The Speed Demon

Bun launched in 2022 with a focus: be fast. It's written in Zig (low-level, fast) and uses JavaScriptCore (Safari's engine) instead of V8.

Strengths:

• Speed: 3-4x faster than Node for many operations
• All-in-one: Runtime + bundler + test runner + package manager
• Node compatibility: Most npm packages work
• DX: Fast installs, fast startup, fast everything
• TypeScript/JSX: Built-in, no config

Weaknesses:

• Maturity: Youngest runtime, more bugs/edge cases
• Windows support: Recently added, less stable
• Ecosystem gaps: Some Node APIs not fully implemented
• Track record: Less production validation

When to use: New projects where speed matters, tooling simplification, when you want bleeding-edge DX.

// Bun - Node compatible, just faster
const server = Bun.serve({
  port: 3000,
  async fetch(req) {
    const file = Bun.file('./data.json');
    return new Response(file, {
      headers: { 'Content-Type': 'application/json' },
    });
  },
});

console.log(`Listening on http://localhost:${server.port}`);

Benchmarks (Real-World)

Everyone shows microbenchmarks. Here's a more realistic test: a REST API that reads from SQLite and returns JSON.

Bun is significantly faster. But note: these numbers matter less than you think. For most apps, the database is the bottleneck, not the runtime.

Where speed differences actually matter:

• Startup time (serverless cold starts)
• Build/bundle times (developer experience)
• Package installation (developer experience)

# Installing dependencies (same project, fresh install)
npm install:  34.2 seconds
pnpm install: 12.1 seconds
bun install:   1.8 seconds

Bun's package manager is absurdly fast.

Package Compatibility

Node: Everything works. It's the standard.

Deno: Excellent npm compatibility now:

import express from 'npm:express';
import chalk from 'npm:chalk';

Most packages work. Some with native modules don't.

Bun: Most npm packages work. Claims Node.js compatibility as a goal. Gaps exist:

• Some native modules (need recompilation)
• Some Node-specific APIs (partial implementation)
• Edge cases in older packages

Check before committing. For mainstream packages (Express, Prisma, React, etc.), all three work.

The Tooling Story

Node's ecosystem:

Runtime: Node.js
Package manager: npm / pnpm / yarn
Bundler: webpack / Vite / esbuild
Test runner: Jest / Vitest
Linter: ESLint
Formatter: Prettier
TypeScript: tsc / ts-node

Deno's all-in-one:

Runtime: deno
Package manager: deno (URL imports or npm: specifiers)
Bundler: deno bundle (deprecated) or esbuild
Test runner: deno test
Linter: deno lint
Formatter: deno fmt
TypeScript: built-in

Bun's all-in-one:

Runtime: bun
Package manager: bun
Bundler: bun build
Test runner: bun test
TypeScript/JSX: built-in
Linter: ESLint (external)
Formatter: Prettier (external)

Deno and Bun reduce tool sprawl. Whether that matters depends on how much you hate configuring tools (I hate it a lot).

My Actual Usage

For work (ON24): Node.js. Stability, ecosystem, team familiarity. No reason to change.

For side projects: Bun. The speed is addictive. bun install taking 2 seconds instead of 30 changes how I prototype.

For security-sensitive scripts: Deno. The permission system is genuinely useful for running untrusted code.

Migration Difficulty

Node → Deno:

• Replace CommonJS with ESM imports
• Update Node-specific APIs to Deno/Web APIs
• Add permission flags
• Medium difficulty, some packages won't work

Node → Bun:

• Usually just works
• Run bun install instead of npm install
• Run bun instead of node
• Low difficulty for most projects

Deno ↔ Bun:

• Deno's URL imports need adjustment
• Permission model differs
• Medium difficulty

Recommendations

Starting a new project today?

Have an existing Node.js project?

Don't migrate unless you have a specific reason:

• Slow builds → Try Bun
• Security requirements → Consider Deno
• Working fine → Stay on Node

Worried about Bun's maturity?

Valid concern. For mission-critical production, Node is safer. But Bun at 1.0+ is stable enough for most use cases. I've been using it without issues.

The Future

All three will coexist. Node isn't going anywhere—too much infrastructure depends on it. Deno has carved out a niche with its security model and Deno Deploy edge platform. Bun is capturing developers who prioritize speed and DX.

Competition is making everyone better. Node is getting faster. Deno improved npm compatibility. Bun is stabilizing.

The best part? Your JavaScript skills transfer across all of them. Learn one, you can use all three.

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I'd recommend trying all three for small projects. Experience beats reading comparisons. `bun init`, `deno init`, and `npm init` all take 30 seconds.