HttpOnly cookies are commonly used to store JWT (JSON Web Token) tokens, which are widely used for web authentication. When using HttpOnly cookies for storing JWT tokens, the token is sent as an HTTP header in the response from the server and is automatically included in subsequent HTTP requests by the browser.

Here’s how it typically works:

1.Login Request:

• • User logs in, the server generates a JWT token.
  • The server sends the JWT token as an HttpOnly cookie in the response.

HTTP/1.1 200 OK
Set-Cookie: jwt_token=; HttpOnly; Path=/

2. Subsequent Requests:

• For every subsequent request to the server, the browser automatically includes the HttpOnly cookie in the request headers.

  GET /some-protected-resource HTTP/1.1
  Cookie: jwt_token=

3. Server-Side Handling:

• The server receives the request and extracts the JWT token from the HttpOnly cookie.
• It verifies the token’s integrity and authenticity.
• Token is valid, the server processes the request.

4. Security Considerations:

• • The HttpOnly attribute prevents the cookie from being accessed through JavaScript. This helps mitigate certain types of attacks, such as cross-site scripting (XSS).

    // This won’t work due to HttpOnly
    const token = document.cookie; // Won’t have access to HttpOnly cookies

  • However, it doesn’t prevent the browser from automatically including the cookie in requests to the same domain.

// This is automatically done by the browser
fetch(‘/some-protected-resource’);

• It’s important to secure the JWT itself. Ensure it’s signed and encrypted appropriately to prevent tampering.

By relying on HttpOnly cookies, you delegate the responsibility of managing the token to the browser. The token is sent automatically with each request, and your frontend code (JavaScript) doesn’t have direct access to it due to the HttpOnly attribute. This is a security measure to reduce the risk of token theft through XSS attacks.