Hello readers 👋, welcome to the 8th blog of our Node.js journey! So far, we've covered how Node.js works under the hood, its event loop, non-blocking code, and how to handle async operations. Now we're going to build something practical that almost every real-world application needs: user authentication using JSON Web Tokens (JWT) . Authentication is how an application knows who you are. You see it every day: logging into a website, accessing private messages, or making a purchase. Today, we'll understand what JWT is, how it works (without diving into complex cryptography), and how to implement a simple, secure login flow in Node.js. Let's get started. What authentication means Authentication is the process of verifying a user's identity. When you log in with a username and password, the server checks those credentials and, if they match, it should remember that you are authenticated for subsequent requests. Without authentication, anyone could pretend to be anyone, and there would be no security.…