What is JWT authentication and how does it work?

JWT (JSON Web Token) is a compact, stateless mechanism for API authentication. When a user logs in, the API server creates a digitally signed, encrypted token containing the user's identity. The client includes this JWT in every subsequent request for validation. The user's data isn't stored server-side, improving scalability. JWT is popular because it allows servers to issue tokens that clients use for future authentication without storing session data. The token contains signed user information that can't be tampered with, making it ideal for securing APIs in stateless environments.