Deno vs Bun: Key Differences and When to Use Each

Both Deno and Bun are modern JavaScript runtimes designed to improve developer experience beyond Node.js. Deno focuses on security, TypeScript support, and a built-in standard library, while Bun emphasizes speed, native bundling, and compatibility with Node.js APIs.

Quick Comparison

This table summarizes the main differences between Deno and Bun across key factors.

Feature	Deno	Bun
Primary Focus	Security and modern APIs	Performance and Node.js compatibility
TypeScript Support	Built-in, first-class	Built-in, fast transpilation
Package Manager	Uses URL imports, no centralized registry	Includes fast native bun install compatible with npm
Performance	Good, but slower than Bun in benchmarks	Very fast startup and execution
Compatibility	Limited Node.js API support	High Node.js API compatibility
Standard Library	Includes a secure, audited std library	Minimal std library, focuses on speed

Key Differences

Deno was created to fix problems seen in Node.js by offering a secure runtime with permissions and a built-in TypeScript compiler. It uses URL-based imports instead of a centralized package manager, which means you import modules directly from the web. This design improves security and simplicity but can feel unfamiliar to developers used to npm.

Bun, on the other hand, is built with performance as the top priority. It includes a native bundler, transpiler, and package manager all in one, making it very fast for starting projects and running code. Bun aims to be highly compatible with existing Node.js projects, so many npm packages work out of the box.

While Deno emphasizes security and a fresh approach to module management, Bun focuses on speed and compatibility, making it easier to switch from Node.js. Both support TypeScript natively, but Bun's transpilation is optimized for speed. Your choice depends on whether you value security and modern design (Deno) or speed and compatibility (Bun).

Code Comparison

Here is a simple example showing how to create a basic HTTP server in Deno.

typescript

import { serve } from "https://deno.land/std@0.203.0/http/server.ts";

serve((_req) => new Response("Hello from Deno!"), { port: 8000 });
console.log("Server running on http://localhost:8000/");

Output

Server running on http://localhost:8000/

Bun Equivalent

The same HTTP server implemented in Bun is even simpler and faster to start.

javascript

import { serve } from "bun";

serve({
  port: 8000,
  fetch(request) {
    return new Response("Hello from Bun!");
  },
});

console.log("Server running on http://localhost:8000/");

Output

Server running on http://localhost:8000/

When to Use Which

Choose Deno when you want a secure runtime with built-in TypeScript support and prefer a modern, permission-based approach to running code. It is great for new projects where security and simplicity matter more than legacy compatibility.

Choose Bun when you need blazing fast startup and execution times, want to use many existing Node.js packages without changes, and prefer an all-in-one toolchain including bundling and package management.

In short, Deno is ideal for secure, modern apps, while Bun excels in speed and compatibility with the Node.js ecosystem.

Key Takeaways

Deno prioritizes security, modern APIs, and built-in TypeScript with URL imports.

Bun focuses on speed, native bundling, and high Node.js compatibility.

Deno uses a permission system and a secure standard library.

Bun includes a fast package manager and supports most npm packages.

Choose Deno for security and modern design; choose Bun for performance and compatibility.