Express.js Online

Learn Node.js

Write an Express server, press Run and send it requests from the request bar: GET, POST, JSON bodies, headers. Nothing to install. Free, no sign-up.

import express from 'express';

const app = express();

app.get('/', (req, res) => {
    res.send('<h1>Hello from Express</h1><p>Send GET /api/hello?name=Ada</p>');
});

app.get('/api/hello', (req, res) => {
    const name = req.query.name || 'world';
    res.json({ message: `Hello, ${name}!` });
});

app.get('/api/users/:id', (req, res) => {
    const id = Number(req.params.id);
    if (!Number.isInteger(id)) {
        return res.status(400).json({ error: 'id must be a number' });
    }
    res.json({ id, name: `User ${id}` });
});

app.listen(3000, () => {
    console.log('Server running on port 3000');
});

Run Express.js online, right in your browser

Edit an Express project beside a running server. Press Run and app.listen(3000) starts it; then send it requests from the request bar: pick the method, type the path, add headers and a JSON body, and see the status, the headers and the answer. It is what you would do with node server.js and curl or Postman, without installing Node.js.

Each example is a whole project, every file editable: server.js and, in the API example, a router in routes/todos.js. The Console shows your console.log() lines, every request and every error with its line. The Routes menu lists what your server answers, and a page your server sends is drawn with working links and forms.

What makes this Express playground useful

The real framework: Express 5 runs your routes, routers, middleware, express.json() and error handlers on a Node.js runtime with fs, process, crypto and events.
A request bar instead of a terminal: GET, POST, PUT, PATCH and DELETE, headers like Authorization, a JSON body, and cookies kept between requests.
A database that needs no server: import { MongoClient } from 'mongodb' gives you an in-memory MongoDB with find, insertOne, indexes and aggregate.
ES modules or CommonJS, as Node.js 24 reads them: import express from 'express' and require('express') both work, with Node's own rules for file extensions.

What you can build in the Express playground

A JSON API: add a route with app.get(), read req.params and req.query, and answer with res.status(201).json().
Middleware: log every request, guard a route with an API key header, then add a 404 handler and an error handler with four arguments.
A small website: send an HTML page with a form, read it with express.urlencoded(), and answer with the page again.

Express.js online FAQ

Can I run Express.js online without installing Node.js?

Yes. This page runs Express in your browser on Coddy's Node.js runtime, in a Web Worker, so there is nothing to install and no account to make. The first Run downloads the runtime once (about 170 KB); after that a server starts in a fraction of a second.

Is this the real Express?

It is Express 5.3, unchanged, running your files. Node's built-in modules are provided by the runtime, so ordinary Express code works: copy your files into a folder on your computer, run npm install express and node server.js, and the server answers the same way.

How do I test my API?

With the request bar above the answer. Choose the method, type the path, and for POST, PUT and PATCH write a JSON body; the Headers button adds headers such as Authorization: Bearer .... The Routes menu fills the bar with a route your server has.

What does the playground not do?

It cannot install packages from npm: Express, zod, jose and an in-memory MongoDB are built in. It cannot open real network connections, reach a database server or the internet, or keep data between Runs: every Run starts a fresh server. It is for learning and trying ideas, not for hosting an API.

Is it free, and is my code saved?

It is free and needs no account. Your edits to each example are kept in this browser, so you can close the tab and come back. Reset puts the current example back the way it started, and the download button saves the open file.

How do I learn Express and Node.js?

Start with the examples here: change a route, press Run, and send it a request. For a path, take Coddy's Node.js course: Node.js basics, Express, REST APIs, MongoDB, authentication and NestJS, with your server running beside your code in every lesson.

Useful tools for Express

Free, browser-based tools that pair well with the Express Playground, all part of Coddy.

Embed the Express editor Compare coding platforms