Authentication API Integration with ReactJS

Authentication is a crucial part of any application. It helps in verifying the identity of users and providing them access to specific resources. In this blog, we will discuss how to integrate an Authentication API with a ReactJS application using a practical example.

Understanding Authentication

Authentication is the process of verifying the identity of a user. When a user logs in to an application, they provide credentials such as a username and password. The server verifies these credentials and if they are valid, the server provides a token to the client. This token is then used for subsequent requests to the server.

Setting Up the ReactJS Application

First, you need to set up your ReactJS application. You can do this by using Create React App, a tool that sets up a new single-page React application with a modern build setup with no configuration.

npx create-react-app auth-app

Creating the Authentication Server

The authentication server is responsible for validating the user’s credentials and generating the token. This server can be created using various backend technologies like Node.js, Express.js, etc.

// server.js

const express = require('express');

const jwt = require('jsonwebtoken');

const app = express();

app.use(express.json());'/login', (req, res) => {

  const { username, password } = req.body;

  // Validate credentials

  // Generate token

  const token = jwt.sign({ username }, 'secret_key');

  res.json({ token });


app.listen(5000, () => console.log('Server started on port 5000'));

Connecting ReactJS to the Authentication Server

Once the server is set up, you can use libraries like Axios or Fetch API to make HTTP requests from your React application. These requests will include the login credentials, and in response, you’ll receive the token.

// Login.js

import React, { useState } from 'react';

import axios from 'axios';

function Login() {

  const [username, setUsername] = useState('');

  const [password, setPassword] = useState('');

  const handleSubmit = async (e) => {


    const { data } = await'/login', { username, password });

    localStorage.setItem('token', data.token);


  return (

    <form onSubmit={handleSubmit}>

      <input type="text" value={username} onChange={(e) => setUsername(} />

      <input type="password" value={password} onChange={(e) => setPassword(} />

      <button type="submit">Login</button>




export default Login;

Handling Tokens in ReactJS

After receiving the token, it should be stored in the client-side storage. Each subsequent request to the server should include this token, usually in the Authorization header.

axios.defaults.headers.common['Authorization'] = `Bearer ${localStorage.getItem('token')}`;

Securing React Routes with Tokens

To protect certain routes in your React application, you can create a protected route component. This component will check if there’s a valid token before rendering the component associated with the route.

// ProtectedRoute.js

import React from 'react';

import { Route, Redirect } from 'react-router-dom';

function ProtectedRoute({ component: Component, }) {

  const token = localStorage.getItem('token');

  return (



      render={(props) =>

        token ? <Component {...props} /> : <Redirect to="/login" />





export default ProtectedRoute;

Token Expiry and Renewal

Tokens should have an expiry time to prevent misuse in case they’re compromised. When a token expires, the server should issue a new one.

Error Handling and Best Practices

Proper error handling is crucial for a good user experience. If a request fails due to an expired or invalid token, the application should handle this gracefully, possibly prompting the user to log in again.

Remember, while token-based authentication offers many benefits, it’s important to handle tokens securely to prevent exposure. Always follow best practices for security.


Integrating an Authentication API with a ReactJS application is a crucial step in ensuring the security of the application. It not only helps in verifying the identity of the users but also in managing access to resources. With the steps mentioned above, you can effectively integrate an Authentication API with your ReactJS application. Happy coding!