H3 Has a Free Minimal HTTP Framework — Here's How to Use It

Express is dated. Fastify is Node-only. H3 is a minimal, ultrafast HTTP framework that runs on Node.js, Bun, Deno, Cloudflare Workers, and every serverless platform.

What Is H3?

H3 is a minimal HTTP framework from the UnJS ecosystem. It powers Nuxt 3 and Nitro but works standalone too. Same code runs everywhere — Node.js, edge runtimes, serverless.

Quick Start

npm install h3

import { createApp, createRouter, defineEventHandler } from 'h3';

const app = createApp();
const router = createRouter();

router.get('/hello', defineEventHandler(() => {
  return { message: 'Hello World!' };
}));

router.post('/users', defineEventHandler(async (event) => {
  const body = await readBody(event);
  return { id: 1, ...body };
}));

app.use(router);

Why H3 Over Express

Feature	H3	Express	Fastify
Runtime	Any	Node.js	Node.js
TypeScript	Native	Manual	Plugin
Bundle size	20KB	200KB	350KB
Edge support	Yes	No	No
JSON handling	Auto	Manual	Auto
Performance	Ultra-fast	Moderate	Fast

Utilities

H3 has built-in utilities for common patterns:

import {
  readBody,          // Parse request body
  getQuery,          // Parse query parameters
  getRouterParam,    // Get route params
  getHeader,         // Get request header
  setHeader,         // Set response header
  setCookie,         // Set cookie
  getCookie,         // Get cookie
  createError,       // Create HTTP error
  sendRedirect,      // Send redirect
  readMultipartFormData, // Handle file uploads
} from 'h3';

router.get('/users/:id', defineEventHandler(async (event) => {
  const id = getRouterParam(event, 'id');
  const query = getQuery(event); // { page: '1', limit: '10' }
  const token = getHeader(event, 'authorization');

  if (!token) {
    throw createError({ statusCode: 401, message: 'Unauthorized' });
  }

  return { id, ...query };
}));

Middleware

app.use(defineEventHandler((event) => {
  // Runs for every request
  console.log(`${event.method} ${event.path}`);
}));

// CORS middleware
app.use(defineEventHandler((event) => {
  setHeader(event, 'Access-Control-Allow-Origin', '*');
}));

WebSocket Support

import { defineWebSocketHandler } from 'h3';

router.get('/ws', defineWebSocketHandler({
  open(peer) {
    console.log('Connected:', peer);
  },
  message(peer, message) {
    peer.send(`Echo: ${message}`);
  },
  close(peer) {
    console.log('Disconnected:', peer);
  },
}));

Deploy Anywhere

// Node.js
import { toNodeHandler } from 'h3';
import { createServer } from 'http';
createServer(toNodeHandler(app)).listen(3000);

// Bun
export default { fetch: toWebHandler(app) };

// Cloudflare Workers
export default { fetch: toWebHandler(app) };

// Deno
Deno.serve(toWebHandler(app));

Get Started

• Documentation
• GitHub — 4K+ stars
• UnJS ecosystem

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