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

Three Runtimes, One Language, Very Different Trade-offs

JavaScript runtimes used to be simple: you installed Node.js and moved on. In 2026, you have three production-viable options -- Node.js, Deno, and Bun -- each with distinct philosophies, performance characteristics, and ecosystem compatibility. I've shipped production code on all three over the past two years, and the "which one should I use?" question doesn't have a one-line answer.

Node.js is the battle-tested incumbent with the largest ecosystem. Deno is the security-first runtime from Node's original creator, now with excellent npm compatibility. Bun is the speed-obsessed newcomer written in Zig that bundles a package manager, test runner, and bundler into a single binary. Each makes real trade-offs, and this guide lays them out with actual benchmarks and practical recommendations.

What Are JavaScript Runtimes?

Definition: A JavaScript runtime is the execution environment that runs your JavaScript (and TypeScript) code outside the browser. It provides the event loop, system APIs (file I/O, networking, child processes), and module resolution. The runtime determines your cold start speed, maximum throughput, available APIs, and how you manage dependencies. Node.js uses V8, Deno uses V8, and Bun uses JavaScriptCore (the engine behind Safari).

Your runtime choice affects everything downstream: deployment size, startup latency, available npm packages, TypeScript workflow, and how your team writes tests. Let's start with the numbers.

Performance Benchmarks (2026)

I ran these benchmarks on an AMD Ryzen 9 7950X with 64 GB DDR5 RAM, running Ubuntu 24.04. Each test was repeated 10 times and averaged. Versions tested: Node.js 22.14, Deno 2.2, Bun 1.2.

HTTP Throughput (Requests/Second)

Using each runtime's built-in HTTP server with a simple JSON response of ~200 bytes. Measured with bombardier at 256 concurrent connections for 30 seconds.

Runtime	Requests/sec	Avg Latency	P99 Latency	Memory Usage
Bun 1.2	312,000	0.82 ms	2.1 ms	38 MB
Deno 2.2	178,000	1.43 ms	3.8 ms	52 MB
Node.js 22	142,000	1.80 ms	5.2 ms	68 MB

Bun's HTTP server is dramatically faster -- roughly 2.2x Node.js and 1.75x Deno. This is largely because Bun's HTTP stack is written in Zig and bypasses much of the JavaScript overhead. However, these are synthetic benchmarks with minimal middleware. In real-world Express/Hono/Fastify apps, the gap narrows considerably because most latency comes from your business logic, database queries, and serialization.

File I/O (Sequential Read/Write)

Reading and writing a 100 MB file 50 times each.

Runtime	Read (MB/s)	Write (MB/s)	Notes
Bun 1.2	4,200	3,800	Uses io_uring on Linux
Node.js 22	2,100	1,900	libuv thread pool
Deno 2.2	1,850	1,700	Tokio async runtime

Bun's file I/O advantage is its most consistent win. The io_uring integration on Linux gives it roughly 2x the throughput of both Node.js and Deno for disk-heavy workloads. On macOS, the gap shrinks to about 1.5x because io_uring isn't available.

SQLite Performance

All three runtimes now ship built-in SQLite support. Inserting 100,000 rows in a single transaction, then querying 10,000 rows by indexed column.

Runtime	Insert (rows/sec)	Query (rows/sec)	API
Bun 1.2	890,000	1,200,000	bun:sqlite
Deno 2.2	620,000	850,000	@db/sqlite
Node.js 22	580,000	780,000	node:sqlite (experimental)

Bun's SQLite implementation is the most mature and fastest. Node.js added node:sqlite as an experimental module in v22.5 -- it works but the API is still evolving. If SQLite is central to your architecture (and it's becoming central to more architectures in 2026), Bun has a real edge.

Cold Start Time

Time from process start to first HTTP response. Measured with hyperfine over 100 runs on a minimal "hello world" server.

Runtime	Cold Start	With TypeScript
Bun 1.2	12 ms	14 ms
Deno 2.2	22 ms	25 ms
Node.js 22	35 ms	280 ms (tsx)

Cold start is where Bun excels the most. Node.js with a TypeScript transpiler like tsx is an order of magnitude slower. Node.js 22's experimental --experimental-strip-types flag gets it down to around 45 ms, but it strips types without checking them. Both Bun and Deno handle TypeScript natively without a separate build step.

npm Compatibility: The Ecosystem Question

npm compatibility is the single most important factor for runtime adoption. Here's where each runtime stands in 2026.

Feature	Node.js 22	Deno 2.2	Bun 1.2
npm registry access	Native	Native (npm: specifiers)	Native
node_modules	Default	Optional (--node-modules-dir)	Default
package.json	Required	Optional	Required
Native addons (N-API)	Full support	Partial (improving)	Partial
Compatibility with top 1000 npm packages	100%	~95%	~93%

Node.js is the reference implementation -- 100% compatibility by definition. Deno 2.x made massive strides with its npm compatibility layer. Most mainstream packages (Express, Prisma, Drizzle, React, Next.js) work out of the box. The remaining 5% failures are usually packages that depend on obscure Node.js internals or native addons using older addon APIs.

Bun's compatibility is slightly behind Deno's. Packages using node:vm, some node:worker_threads edge cases, and certain native addons still fail. The Bun team ships compatibility fixes weekly, so this gap is closing fast.

TypeScript Support Compared

TypeScript handling is one of the starkest differences between the three runtimes.

// This file works in all three runtimes -- but HOW it works differs

interface User {
  id: number;
  name: string;
  email: string;
}

function greet(user: User): string {
  return `Hello, ${user.name}`;
}

// Node.js 22: requires --experimental-strip-types or external tool (tsx, ts-node)
// Deno 2.2: runs natively, type-checks with deno check
// Bun 1.2: runs natively, strips types (no type checking at runtime)
console.log(greet({ id: 1, name: 'Alice', email: 'alice@example.com' }));

Feature	Node.js 22	Deno 2.2	Bun 1.2
Run .ts files directly	Experimental (--experimental-strip-types)	Yes	Yes
Type checking at runtime	No	Yes (deno check)	No
tsconfig.json support	Yes (via tooling)	Yes (with overrides)	Yes
JSX/TSX support	No (needs transpiler)	Yes	Yes
Path aliases	Via tsconfig paths	Via import maps	Via tsconfig paths

Deno is the only runtime that can both run and type-check your TypeScript. Bun and Node.js (with strip-types) simply remove the type annotations before execution -- you still need tsc or a similar tool in your CI pipeline for actual type safety.

Package Management: Three Different Approaches

Each runtime has a distinct philosophy about dependency management.

Node.js: npm, pnpm, or yarn

# Node.js -- choose your package manager
npm install express
pnpm add express
yarn add express

# Lock files: package-lock.json, pnpm-lock.yaml, yarn.lock

Deno: URL Imports + npm Specifiers

// Deno -- multiple import styles
import { Hono } from 'npm:hono';               // npm specifier
import { serve } from 'jsr:@std/http';          // JSR registry
import { z } from 'https://deno.land/x/zod/mod.ts'; // URL import (legacy)

// Lock file: deno.lock (auto-generated)

Bun: Built-in Package Manager

# Bun -- fastest install times
bun add express        # ~5x faster than npm install
bun install            # installs from package.json

# Lock file: bun.lockb (binary format, fast to parse)

Bun's package manager is consistently the fastest. Installing a fresh node_modules for a medium-sized project (200+ dependencies) takes roughly 1.2 seconds with Bun, 5.8 seconds with pnpm, and 12+ seconds with npm. The binary lockfile is controversial -- you can't review it in pull requests -- but bun install --yarn generates a readable yarn.lock if you need one.

Bundler and Test Runner Comparison

Bun and Deno both ship integrated tooling. Node.js relies on the ecosystem.

Tool	Node.js 22	Deno 2.2	Bun 1.2
Test runner	node --test (built-in)	deno test	bun test
Bundler	None (use Vite, esbuild, Rollup)	deno bundle (deprecated, use esbuild)	bun build
Formatter	None (use Prettier, Biome)	deno fmt	None (use Prettier, Biome)
Linter	None (use ESLint, Biome)	deno lint	None (use ESLint, Biome)
Benchmarking	None	deno bench	None

Deno provides the most complete built-in toolchain. deno fmt, deno lint, deno test, and deno bench mean you can start a project with zero config and zero dev dependencies. Bun's test runner is Jest-compatible -- your existing .test.ts files usually work without changes, and it runs 10-20x faster than Jest. Node.js 22's built-in test runner has matured significantly but still lacks the ergonomics of bun test or deno test.

// Test file that works across all three runtimes
// bun test / deno test / node --test

import { describe, it, expect } from 'bun:test'; // Bun
// import { assertEquals } from '@std/assert';    // Deno
// import { describe, it } from 'node:test';      // Node.js

describe('math', () => {
  it('adds numbers', () => {
    expect(1 + 1).toBe(2);
  });
});

Security Model

This is Deno's killer feature and the area where Node.js and Bun trail badly.

Capability	Node.js 22	Deno 2.2	Bun 1.2
Network access	Unrestricted	Requires --allow-net	Unrestricted
File system access	Unrestricted	Requires --allow-read/--allow-write	Unrestricted
Environment variables	Unrestricted	Requires --allow-env	Unrestricted
Subprocess execution	Unrestricted	Requires --allow-run	Unrestricted
Permission granularity	None	Per-domain, per-path	None

Deno's permission system means a compromised npm package can't silently exfiltrate data or write to your filesystem. You explicitly grant --allow-net=api.example.com or --allow-read=./data. In a world where supply chain attacks are increasingly common, this is a genuine security advantage. Node.js has an experimental permissions model (--experimental-permission), but it's nowhere near as mature or ergonomic as Deno's.

Stability and Enterprise Readiness

Production stability matters more than benchmark numbers. Here's an honest assessment based on running all three in production environments.

Node.js: The Safe Choice

Node.js is the only runtime with a formal LTS (Long Term Support) schedule. Node 22 is the current LTS with support through April 2027. Every Fortune 500 company using JavaScript on the server runs Node.js. The ecosystem tooling -- PM2, clinic.js, 0x, APM integrations -- is unmatched. If your organization requires SOC 2 compliance documentation or vendor support contracts, Node.js is your only realistic option.

Deno: Ready for Production

Deno 2.x was a turning point. The npm compatibility layer, package.json support, and Node.js API polyfills made migration practical. Deno Deploy offers a serverless edge platform. Companies like Netlify (Edge Functions) and Supabase (Edge Functions) run Deno in production at scale. It's ready -- but your team needs to accept that some niche npm packages won't work, and community resources are thinner than Node.js.

Bun: Fast but Evolving

Bun has been stable enough for production since 1.0 (September 2023), and version 1.2 fixed many of the early rough edges. However, edge cases still surface. I've hit unexpected behavior in node:cluster emulation and occasional segfaults in long-running worker thread scenarios. Bun is excellent for dev tooling (scripts, tests, builds), API servers with moderate complexity, and greenfield projects. I wouldn't migrate a critical, complex Node.js monolith to Bun today -- but I'd absolutely start a new microservice on it.

When to Use Each Runtime

After two years of using all three in production, here's my practical decision framework:

1. Choose Node.js when you need maximum ecosystem compatibility, LTS guarantees, enterprise support, or your team already has deep Node.js expertise. It's the safe default and there's nothing wrong with safe.
2. Choose Deno when security is a priority, you want an all-in-one toolchain (formatter, linter, tester), you're deploying to the edge, or you're starting a new project and want modern defaults without legacy baggage.
3. Choose Bun when raw performance matters (high-throughput APIs, file-heavy workloads), you want the fastest dev experience (instant installs, fast tests), or you're building tooling and scripts where startup time is critical.

The good news: all three run the same language and increasingly share the same package ecosystem. Switching between them is getting easier every month. Write standard JavaScript/TypeScript, avoid runtime-specific APIs where possible, and you'll have options.

Frequently Asked Questions

Can I use Express.js with Bun and Deno?

Yes. Express runs on all three runtimes. Bun and Deno both implement enough of the Node.js http module to support Express. However, for best performance on Bun and Deno, consider using Hono -- a lightweight framework designed to be runtime-agnostic with optimized adapters for each.

Is Bun ready for production in 2026?

For most workloads, yes. Bun 1.2 resolved the majority of stability issues from earlier versions. It's being used in production by thousands of companies for API servers, build tooling, and background workers. The main risk areas are complex node:cluster setups and certain native addon edge cases. Test thoroughly before migrating a large existing codebase.

Does Deno still require permission flags for everything?

Yes, by default. Deno runs with no permissions -- you must explicitly grant network, file system, and environment access. You can use deno run -A to allow everything (equivalent to Node.js/Bun behavior), or define granular permissions in a deno.json config file so you don't have to type flags every time. The permission model is a feature, not a limitation.

Which runtime has the best TypeScript support?

Deno has the most complete TypeScript integration -- it runs, type-checks, and formats TypeScript natively. Bun runs TypeScript natively but doesn't type-check (it strips types). Node.js 22 has experimental type stripping but still relies on external tools for a complete TypeScript workflow. For day-to-day development, Bun and Deno are equally convenient; Deno edges ahead if you want built-in type checking.

How do I migrate a Node.js project to Bun?

Start by running bun install instead of npm install -- this alone gives you faster installs. Then try bun run your-script.ts. Most projects work immediately. Common migration issues include: packages using node:vm (limited support in Bun), native addons not yet ported, and node:diagnostics_channel edge cases. Run your test suite with bun test and fix failures incrementally.

What about Windows support?

Node.js has the best Windows support -- it's a first-class platform. Deno works well on Windows with full feature parity. Bun added Windows support in version 1.0.3 and it's functional but less battle-tested than Linux or macOS. If Windows is your primary development or deployment OS, Node.js is the safest choice. For production servers, all three target Linux primarily.

Can I use all three runtimes in the same project?

Yes, and many teams do. A common pattern is using Bun for local development (fast installs, fast tests), Node.js for production deployment (LTS stability), and Deno for edge functions or security-sensitive scripts. As long as you avoid runtime-specific APIs in shared code, this works well. Use conditional imports or adapter patterns for runtime-specific features.