Tech Comparisons
JWT vs Session
Two fundamentally different approaches to user authentication. Understanding the trade-offs is crucial for building secure, scalable applications.
| Feature | JWT | Session |
|---|---|---|
| Storage | Server-side session store (Redis, database, memory). | Client-side storage (localStorage, cookies). Self-contained token. |
| Scalability | Requires sticky sessions or shared session store. | Stateless, works seamlessly across multiple servers. |
| Security | Session ID is opaque, payload stored server-side. | Payload is visible (Base64 encoded). Requires HTTPS. |
| Revocation | Easy to revoke by deleting server session. | Difficult to revoke before expiration without a blacklist. |
| Size | Small session ID sent with each request. | Larger token payload sent with each request. |
JWT Pros & Cons
Pros
- Easy to revoke access instantly
- Smaller cookie/header size
- Server controls all session data
- Easier to manage active sessions
Cons
- Requires server-side storage
- Difficult to scale horizontally
- Needs session synchronization across servers
Session Pros & Cons
Pros
- Stateless and horizontally scalable
- No server-side storage needed
- Cross-domain authentication (CORS)
- Mobile-friendly (no cookies required)
Cons
- Difficult to revoke before expiry
- Larger request headers
- Vulnerable if not using HTTPS
- Token refresh complexity
Verdict
Use JWT for stateless, scalable APIs, microservices, and mobile apps where horizontal scaling is important. Use sessions for traditional web apps with tight security requirements where instant revocation is critical. Many modern apps use a hybrid approach: short-lived JWTs with refresh tokens stored server-side.