"Should I use JWTs or sessions?" is the wrong question. The right question is "What are my requirements?"
The Session-Based Pattern
Server stores session data. Client gets a session ID in a cookie. Simple, proven, well-understood.
Advantages:
Server can invalidate sessions instantly. User logs out everywhere immediately.
Session data stays server-side. Client can't tamper with it.
Works naturally with HTTP-only cookies. Better XSS protection.
Disadvantages:
Server state required. Every request needs session lookup.
Scaling complexity. Sessions need shared storage across servers.
Cookie limitations for cross-domain scenarios.
The JWT Pattern
Token contains claims, signed by server. Client stores and sends token. Server verifies signature without state.
Advantages:
Stateless on the server. No session storage needed.
Works well for APIs. Easy to use in headers.
Cross-domain friendly. Not tied to cookies.
Disadvantages:
Can't truly revoke tokens before expiry. Only workarounds (blocklists, short expiry).
Token size. JWTs are larger than session IDs.
Complexity. Refresh tokens, token storage decisions, signature algorithms.
When to Choose Sessions
Traditional web apps with server rendering. Sessions work naturally with cookies.
You need instant invalidation. Logout must mean logout.
Simpler security model preferred. Fewer moving parts to secure.
When to Choose JWTs
API-first architectures. Mobile apps, SPAs talking to APIs.
Microservices. Services can verify tokens without central session store.
Short-lived authorisation. Where token expiry is acceptable revocation.
The Hybrid Approach
Many systems use both. Sessions for web clients, JWTs for API access. Refresh tokens for mobile apps.
Security Fundamentals (Either Way)
Use HTTPS everywhere. Authentication without encryption is theatre.
Hash passwords properly. bcrypt, Argon2. Never MD5 or SHA1.
Rate limit authentication endpoints. Prevent brute force.
Implement proper logout. Don't just clear client state.
At Logic Leap, we help teams implement authentication correctly the first time. Security architecture questions? Let's talk.
What authentication patterns have worked for you?
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