Enabling Cookies with Axios Requests

Axios is a popular JavaScript library used for making HTTP requests. When working with APIs that utilize cookies for authentication or state management, it’s crucial to ensure that Axios automatically includes these cookies in outgoing requests. This tutorial explains how to achieve this, covering both client-side configuration and server-side requirements.

Understanding the Role of Cookies

Cookies are small text files stored by the browser to remember information about the user or their session. They are often used for authentication (keeping a user logged in) and personalization. When a server sets a cookie, the browser will automatically include it in subsequent requests to that server. However, in modern web applications, especially those employing cross-origin requests, specific configurations are needed to ensure this automatic inclusion works as expected.

Client-Side Configuration with Axios

Axios provides a simple mechanism to control whether cookies are included in requests via the withCredentials option.

1. Per-Request Configuration:

You can enable cookies for a single request by including the withCredentials: true option in the request configuration:

axios.get('/api/data', {
  withCredentials: true
})
.then(response => {
  // Handle the response
  console.log(response.data);
})
.catch(error => {
  // Handle errors
  console.error(error);
});

2. Global Configuration:

For applications where you consistently need to send cookies, it’s more convenient to set withCredentials globally for all Axios requests. This can be done by modifying axios.defaults:

axios.defaults.withCredentials = true;

Place this line of code early in your application’s initialization to ensure all subsequent Axios requests include cookies.

3. Axios Instance Configuration:

For more complex applications, you might use multiple Axios instances with different configurations. You can set withCredentials during the creation of an Axios instance:

const instance = axios.create({
  baseURL: '/api',
  withCredentials: true
});

instance.get('/data')
  .then(response => {
    // Handle response
  })
  .catch(error => {
    // Handle error
  });

This approach allows you to maintain different configurations for different parts of your application.

Server-Side Requirements (Express.js Example)

Enabling withCredentials on the client-side is not enough. The server must also be configured to allow cross-origin requests with credentials. This is done using appropriate HTTP headers. Here’s how to configure an Express.js server:

const express = require('express');
const cookieParser = require('cookie-parser');

const app = express();
const port = 3000;

// Middleware to parse cookies
app.use(cookieParser());

// Enable CORS with credentials for the frontend origin
app.use((req, res, next) => {
  res.header('Access-Control-Allow-Origin', 'http://localhost:8080'); // Replace with your frontend origin
  res.header('Access-Control-Allow-Credentials', 'true');
  res.header('Access-Control-Allow-Headers', 'Origin, X-Requested-With, Content-Type, Accept');
  next();
});

app.get('/api/data', (req, res) => {
  // Access cookies via req.cookies
  const myCookie = req.cookies.myCookie; 

  res.json({ message: 'Data from server', cookie: myCookie });
});

app.listen(port, () => {
  console.log(`Server listening on port ${port}`);
});

Important considerations:

Access-Control-Allow-Origin: This header specifies the origin (domain, protocol, and port) that is allowed to make cross-origin requests. Replace http://localhost:8080 with the actual origin of your frontend application. Using * as a wildcard is generally discouraged in production environments as it weakens security.
Access-Control-Allow-Credentials: This header must be set to true to allow the browser to send cookies with cross-origin requests.
Access-Control-Allow-Headers: This header specifies which headers are allowed in the cross-origin request. Include any custom headers your frontend application might be sending.
Cookie Parser Middleware: Ensure you are using cookie-parser middleware (app.use(cookieParser())) on the server to parse incoming cookies from the request headers. This allows you to access cookies via req.cookies.

Troubleshooting

Cookies Not Being Sent: Double-check that both the client-side withCredentials option and the server-side CORS headers are configured correctly. Inspect the browser’s network tab to verify whether the cookies are being included in the request headers.
CORS Errors: If you encounter CORS errors, ensure that the Access-Control-Allow-Origin header matches the origin of your frontend application. Also, verify that you have included any necessary custom headers in the Access-Control-Allow-Headers header.
Incorrect Cookie Parsing: Make sure you are using cookie-parser middleware on the server to parse the cookies from the request headers.