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 and native bundling with a built-in package manager.

Quick Comparison

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

Factor	Deno	Bun
Primary Focus	Secure runtime with built-in TypeScript support	High-performance runtime with fast bundling and native package manager
Language Support	JavaScript and TypeScript out of the box	JavaScript, TypeScript, and JSX support
Package Management	No centralized package manager; uses URL imports	Built-in fast package manager compatible with npm
Performance	Good startup time, slower than Bun in benchmarks	Very fast startup and execution, optimized for speed
Standard Library	Comprehensive built-in standard library	Smaller standard library, relies more on npm ecosystem
Security Model	Secure by default with explicit permissions	Less strict security model, focused on speed

Key Differences

Deno was created to fix Node.js issues by providing a secure runtime that requires explicit permission for file, network, and environment access. It has first-class TypeScript support without extra setup and includes a rich standard library for common tasks. This makes Deno great for projects where security and simplicity matter.

Bun, on the other hand, is built for speed. It uses a JavaScriptCore engine and includes a native bundler and package manager, making it very fast for running scripts and managing dependencies. Bun supports JSX and is designed to replace multiple tools in the JavaScript ecosystem with one fast runtime.

While Deno emphasizes security and a stable API, Bun focuses on performance and developer productivity with built-in tools. Your choice depends on whether you prioritize security and built-in features (Deno) or speed and integrated tooling (Bun).

Code Comparison

Here is a simple example showing how to create an 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 in Bun is 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 need a secure runtime with built-in TypeScript support and a rich standard library, especially for projects where security and stability are priorities.

Choose Bun when you want the fastest startup and execution times, integrated bundling, and package management, making it ideal for rapid development and performance-critical applications.

Both are modern and evolving, so consider your project needs and ecosystem preferences before deciding.

Key Takeaways

Deno prioritizes security and built-in TypeScript support with a comprehensive standard library.

Bun focuses on speed with a native bundler and package manager for fast development.

Deno requires explicit permissions for file and network access, enhancing safety.

Bun offers faster startup and execution, ideal for performance-sensitive projects.

Choose based on whether you value security and features (Deno) or speed and tooling (Bun).