Authentication in Web Apps: JWT, Sessions, and OAuth Explained

Authentication is one of those topics that every web developer eventually needs to understand. The two traditional approaches are session-based authentication and JSON Web Tokens (JWT). Sessions store user data on the server, usually in a database or Redis cache, and send a session ID cookie to the client. They're straightforward and easy to invalidate, but they require server-side storage and can be problematic in serverless environments. JWTs are stateless tokens containing encoded user information. The server signs them, and the client stores them (usually in localStorage or HTTP-only cookies). They're great for distributed systems, but token invalidation is trickier. The modern approach often uses OAuth 2.0 and OpenID Connect, letting users authenticate through providers like Google or GitHub. This delegates the complexity of password storage and MFA to experts. For your own apps, start with a well-tested library like Passport.js for Node.js, Django's authentication system, or Firebase Auth. Always use HTTPS, store passwords properly using bcrypt or Argon2, and implement CSRF protection for state-changing requests. Remember that authentication is security-critical—prefer battle-tested solutions over rolling your own.