APIs power almost everything on the internet.
From mobile apps and SaaS platforms to eCommerce stores and CRMs — they all rely on APIs to send and receive data.
In this tutorial, you’ll learn how to build a simple REST API using Node.js and Express in under 30 minutes.
No fluff. Just practical steps.
What We’re Building
We’ll create a basic API that:
- Returns a list of users
- Allows you to add a new user
- Responds with JSON
- Runs locally on your machine
Step 1: Install Node.js
If you don’t already have it installed, download Node.js from:
To confirm installation, run:
node -v
npm -v
If you see version numbers, you’re ready.
Step 2: Create a New Project
Create a new folder:
mkdir simple-api
cd simple-api
Initialize a Node project:
npm init -y
This creates your package.json file.
Step 3: Install Express
Now install Express:
npm install express
Express is a minimal web framework that makes building APIs easy.
Step 4: Create Your Server File
Create a file called:
index.js
Add the following code:
const express = require("express");
const app = express();
const PORT = 3000;
// Middleware to parse JSON
app.use(express.json());
// Temporary in-memory data
let users = [
{ id: 1, name: "John" },
{ id: 2, name: "Sarah" }
];
// GET route - Fetch all users
app.get("/users", (req, res) => {
res.json(users);
});
// POST route - Add new user
app.post("/users", (req, res) => {
const newUser = {
id: users.length + 1,
name: req.body.name
};
users.push(newUser);
res.status(201).json(newUser);
});
// Start server
app.listen(PORT, () => {
console.log(`Server running on http://localhost:${PORT}`);
});
Step 5: Run the Server
In your terminal:
node index.js
You should see:
Server running on http://localhost:3000
Step 6: Test Your API
Test GET Request
Open your browser and go to:
http://localhost:3000/users
You should see:
[
{ "id": 1, "name": "John" },
{ "id": 2, "name": "Sarah" }
]
Test POST Request
Use a tool like Postman or VS Code Thunder Client.
Send a POST request to:
http://localhost:3000/users
With JSON body:
{
"name": "Michael"
}
You should get:
{
"id": 3,
"name": "Michael"
}
And if you refresh /users, the new user appears.
What Just Happened?
You built a working REST API with:
- Express server
- JSON middleware
- GET endpoint
- POST endpoint
- Basic data storage
This is the foundation of:
- SaaS platforms
- Mobile backends
- Admin dashboards
- CRM systems
- Custom business tools
Next Steps
To level this up, you can:
- Add PUT and DELETE routes
- Connect to MongoDB or PostgreSQL
- Add validation
- Add authentication
- Use environment variables
- Deploy to a cloud platform
