Create Rest API: A Beginner’s Guide

Modern applications often need to exchange data across platforms, web, mobile, and third-party services. Without a structured approach to handling this communication, developers face challenges such as inconsistent data formats, complex integrations, and limited scalability. This is where the REST API helps.

This article explores setting up the environment, building a REST API, and testing it with the Requestly API Client.

What is REST API?

A REST API (Representational State Transfer Application Programming Interface) is a way for applications to communicate with each other over the web using standard HTTP methods. Instead of sending entire pages, it exposes resources like users, products, or orders as endpoints that can be created, read, updated, or deleted.

Key aspects include:

• Resource-based: Everything is treated as a resource accessible via a URL (e.g., /users/1).
• HTTP methods: GET, POST, PUT/PATCH, and DELETE are used for CRUD operations.
• Stateless: Each request contains all the information the server needs, with no session stored.
• Format: Data is usually exchanged in JSON for simplicity and compatibility.

REST APIs make applications scalable, maintainable, and easy to integrate across platforms.

Planning Your API

Before writing any code, it’s important to plan how your API will work. A well-thought-out design ensures scalability, consistency, and easier maintenance.

Key steps in planning include:

• Identify resources: Start by defining the main entities your API will manage, such as users, products, or orders.
• Design endpoints: Map each resource to clear and predictable URIs like /users, /users/{id}, or /products/{id}.
• Choose a data format: Decide on a standard format for data exchange; JSON is the most widely used for simplicity and compatibility.
• Define request/response structures: Establish consistent patterns for how clients send data and how the API will respond.
• Set status codes: Determine which HTTP status codes to use for success and error cases (e.g., 200 OK, 201 Created, 404 Not Found).
• Plan for versioning: Include versioning in your design (e.g., /api/v1/) to make future updates easier without breaking existing clients.

How to Set Up the Environment

Before creating a REST API, you need to prepare your development environment. This ensures that the required tools, frameworks, and dependencies are in place.

Steps to set up the environment:

• Install a runtime: Choose a platform like Node.js, Python, or Java, depending on your preferred stack.
• Set up a package manager: Use tools like npm (Node.js), pip (Python), or Maven/Gradle (Java) to manage dependencies.
• Create a project directory: Organize your codebase with a dedicated folder structure for clarity and maintainability.
• Initialize the project: Run commands such as npm init or pip install to start managing project dependencies.
• Install a web framework: Add a lightweight framework such as Express (Node.js), Flask (Python), or Spring Boot (Java) to simplify API creation.
• Verify the setup: Run a “Hello World” server to confirm everything is configured correctly.

Example: Setting Up with Node.js and Express

Follow the steps below to quickly set up a REST API using Node.js and Express:

1. Install Node.js: Download and install from nodejs.org.

2. Verify installation:

node -v

npm -v

3. Create a project folder

 mkdir rest-api-demo

cd rest-api-demo

4. Initialize the project

 npm init -y

5. Install Express

 npm install express

6. Create a basic server

In index.js:

 const express = require("express");

const app = express();

const PORT = 3000;



app.get("/", (req, res) => {

  res.send("Hello World! REST API is ready.");

});



app.listen(PORT, () => {

  console.log(`Server running on http://localhost:${PORT}`);

});

7. Run the server

 node index.js

8. Test in browser

Open http://localhost:3000 and you should see “Hello World! REST API is ready.”

Steps to Create a Simple REST API

Once the environment is ready, you can start building a basic REST API. Below is a step-by-step guide with a simple Node.js + Express example.

1. Initialize the server

Create a new folder, initialize the project, and install a web framework like Express (Node.js) or Flask (Python).

const express = require("express");

const app = express();

app.use(express.json()); // to parse JSON bodies

const PORT = 3000;



app.listen(PORT, () => {

  console.log(`Server running on http://localhost:${PORT}`);

});

2. Create sample data

To work with your API, start by defining some sample data as shown below:

let users = [

  { id: 1, name: "Alice" },

  { id: 2, name: "Bob" }

];

3. Implement CRUD endpoints

Next, implement the CRUD endpoints to handle create, read, update, and delete operations:

GET – Retrieve all users

app.get("/users", (req, res) => {

  res.json(users);

});

GET by ID – Retrieve a single user

app.get("/users/:id", (req, res) => {

  const user = users.find(u => u.id === parseInt(req.params.id));

  user ? res.json(user) : res.status(404).send("User not found");

});

POST – Add a 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);

});

PUT – Update an existing user

app.put("/users/:id", (req, res) => {

  const user = users.find(u => u.id === parseInt(req.params.id));

  if (!user) return res.status(404).send("User not found");

  user.name = req.body.name;

  res.json(user);

});

DELETE – Remove a user

app.delete("/users/:id", (req, res) => {

  users = users.filter(u => u.id !== parseInt(req.params.id));

  res.status(204).send();

});

4. Test the API

Open http://localhost:3000/users in the browser to see the list.

Testing your REST API with Requestly API Client

Once your API endpoints are ready, the next step is to test them to ensure they work as expected. The Requestly API Client makes this process simple and beginner-friendly. Unlike heavy desktop tools, it runs directly in your browser, so you can start testing instantly without extra installations.

With Requestly API Client, you can:

• Send API requests using different HTTP methods like GET, POST, PUT, and DELETE.
• Inspect responses including status codes, headers, and JSON payloads.
• Add custom headers or body data to simulate real-world scenarios.
• Save and organize requests into collections for quick reuse.
• Share collections with teammates to collaborate on API testing.

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Following REST Best Practices

The following best practices help ensure your REST API is consistent, reliable, and easy to use:

• Use resource‑based, noun URIs: Prefer /users, /users/{id} over verb URIs like /getUsers. Keep naming consistent and plural.
• Example: /orders/42/items
• Map actions to HTTP methods: GET (read), POST (create), PUT/PATCH (update), DELETE (remove). Avoid custom verbs in paths.
• Return proper status codes: Use 201 Created (with Location header) on create, 200 OK/204 No Content on success, 400/401/403/404/409/422/429/5xx for errors.
• Keep requests stateless: Every request includes all info needed (auth, params). Don’t rely on server sessions.
• Design predictable responses: Use consistent JSON shapes and types. Include id, timestamps, and links where helpful.
• Use ETags and caching headers: Add ETag, Cache-Control, and support conditional requests (If-None-Match) to improve performance.
• Validate input and return clear errors: Respond with a consistent error format (code, message, details) and Content-Type: application/json.

Conclusion

Creating a REST API may seem complex at first, but with the right approach, it becomes a straightforward process. By carefully planning your resources, setting up the environment, and building CRUD endpoints step by step, you can establish a solid foundation for communication between applications.

Testing tools like the Requestly API Client make it easier to validate requests and responses during development, while following REST best practices ensures scalability, security, and consistency.

A well-designed REST API not only simplifies integrations but also lays the groundwork for building reliable, future-ready applications.