Bun vs Node.js vs Deno: JavaScript Runtime Comparison

Bun vs Node.js vs Deno: JavaScript Runtime Comparison

The JavaScript runtime landscape has gone from a Node.js monopoly to a three-way competition. Bun, Node.js, and Deno each take a different stance on performance, compatibility, and developer experience. Here's an honest comparison based on real-world usage, not benchmarks-game numbers.

The Quick Summary

Performance: What Actually Matters

Bun wins synthetic benchmarks by a wide margin. Its HTTP server handles more requests per second, its startup time is faster, and bun install is dramatically quicker than npm install. Some of this comes from JavaScriptCore (WebKit's engine), some from aggressive optimization in Zig.

But synthetic benchmarks rarely reflect real workloads. In a typical web application, your bottleneck is database queries, network I/O, and business logic -- not runtime overhead. The places where Bun's speed genuinely matters in practice:

• Package installation: bun install is 5-10x faster than npm install. This adds up in CI pipelines. If you're running dozens of builds per day, switching to Bun just for installation saves meaningful time.
• Startup time: Bun starts scripts noticeably faster than Node.js. For CLI tools, serverless cold starts, and development scripts, this is tangible.
• Test execution: bun test runs test suites faster than Jest or Vitest due to lower startup overhead and native TypeScript support.

Node.js and Deno have roughly comparable runtime performance since they both use V8. Node.js has had years of optimization for specific patterns (streams, HTTP, Buffer), so it can actually outperform Bun in some I/O-heavy scenarios.

Package Management

Node.js Ecosystem (npm/yarn/pnpm)

The npm registry is the largest package ecosystem in any language. Node.js gives you choice: npm (default), yarn (workspaces pioneer), or pnpm (disk-efficient, strict). pnpm is the best choice for most teams today -- it's fast, correct about dependency hoisting, and has excellent workspace support.

Bun

bun install is compatible with package.json and node_modules. It reads your existing lockfile and generates a bun.lockb (binary lockfile) or bun.lock (text, as of Bun 1.2). It supports workspaces and handles most npm packages correctly.

The main pain point: some packages with native addons compiled for Node.js don't work with Bun. The compatibility gap has narrowed significantly, but you'll occasionally hit a package that assumes Node.js internals.

Deno

Deno originally used URL-based imports without a package manager. That was... not popular. Deno 2.0 course-corrected with full npm compatibility via npm: specifiers and a deno add command that manages a deno.json import map. You can also use a package.json directly.

// Deno with npm packages
import express from "npm:express@4";

This works, but the ecosystem friction hasn't fully disappeared. Some packages assume Node.js globals or APIs that Deno's compatibility layer doesn't cover.

TypeScript Support

Bun and Deno both run TypeScript natively -- no build step, no configuration. This is a genuine quality-of-life improvement over Node.js, where you've historically needed tsx, ts-node, or a compilation step.

Node.js added --experimental-strip-types in v22 and made it stable for .ts files in v23.6. It strips types but doesn't handle TypeScript-specific syntax like enum or namespace. For most modern TypeScript code, this works fine.

Important caveat: none of these runtimes type-check at execution time. They all strip types and run JavaScript. You still need tsc --noEmit or an editor for actual type safety.

Compatibility and Ecosystem

Node.js has the deepest ecosystem compatibility by far. Every npm package is built for Node.js. Every deployment platform supports it. Every tutorial assumes it. This matters more than benchmarks for production applications.

Bun targets Node.js API compatibility and achieves it for most packages. The node: built-in modules are largely implemented. But "largely" is the key word -- if your application depends on less common Node.js APIs (vm module edge cases, specific crypto behaviors, native addon ABIs), you may hit gaps.

Deno's compatibility has improved enormously with Deno 2.0. The npm: specifier system works for most packages. But the experience can still feel like using a compatibility layer rather than native support, especially for packages that rely on Node.js-specific patterns.

Built-in Tooling Comparison

Testing

# Node.js (built-in, minimal)
node --test src/**/*.test.ts

# Bun (Jest-compatible API)
bun test

# Deno (built-in, permissions-aware)
deno test

Bun's test runner uses a Jest-compatible API (describe, it, expect), making migration from Jest straightforward. Deno's test runner uses its own API. Node.js's built-in test runner works but lacks the ergonomics of either.

Formatting and Linting

Deno ships deno fmt and deno lint built-in. This is convenient but less configurable than Biome or ESLint. Bun and Node.js rely on external tools.

Bundling

Bun includes a bundler (bun build) that handles JSX, TypeScript, and tree-shaking. It's fast but less mature than esbuild, Vite, or Rollup. For production bundling, you'll likely still want a dedicated tool.

Security Model

Deno's permission system requires explicit grants for file system, network, and environment access:

deno run --allow-net --allow-read=./data src/server.ts

This is genuinely useful for running untrusted code or enforcing least-privilege in production. Neither Node.js nor Bun offers an equivalent. Node.js has an experimental permission model, but it's not widely adopted.

The trade-off: permissions add friction during development. You'll spend time figuring out which permissions a dependency needs, especially for complex packages.

When to Choose Each

Choose Node.js When:

• You need maximum ecosystem compatibility (every package, every platform)
• Your team knows Node.js and switching cost isn't justified
• You depend on native addons (N-API)
• You're deploying to platforms that only support Node.js
• You need battle-tested production stability

Choose Bun When:

• You want the fastest development experience (install, startup, testing)
• You're building a new project and can accept some compatibility risk
• CI pipeline speed matters (faster installs, faster tests)
• You're writing TypeScript and want zero-config execution
• Your dependencies are all pure JavaScript/TypeScript (no native addons)

Choose Deno When:

• Security permissions matter for your use case
• You want built-in formatting, linting, and testing without external tools
• You're building edge/serverless functions (Deno Deploy is compelling)
• You prefer web-standard APIs over Node.js-specific ones
• You're starting a new project and value a "batteries included" runtime

The Practical Recommendation

For most teams in 2026, Node.js remains the safe default for production services. The ecosystem depth, deployment support, and institutional knowledge are unmatched.

Bun is the strongest choice for development tooling -- use it for running scripts, installing packages, and running tests even if your production runtime is Node.js. The speed improvements are real and daily.

Deno is excellent for specific niches: edge functions (Deno Deploy), security-sensitive scripts, and standalone tools. Its "batteries included" philosophy means less configuration for small projects.

The runtimes are converging on compatibility. Bun and Deno both invest heavily in Node.js API support. Node.js is adopting features that Bun and Deno pioneered (native TypeScript, built-in testing, permission model). The long-term trend is toward runtime portability, which benefits everyone.