Overview
After a user logs in, you need to remember them on later requests — and the two dominant approaches differ in where the state lives. Server-side sessions store the session in a database or Redis and hand the browser an opaque cookie; every request looks it up, which makes revocation instant but adds a read per request and shared state to scale. JWTs (JSON Web Tokens) pack the user's claims into a signed token the client carries; the server verifies the signature with no lookup — great for stateless, distributed services — but you can't easily revoke a token before it expires.
JWT vs Session: key differences
| JWT | Session | |
|---|---|---|
| State | Self-contained, none on server | Stored server-side (DB/Redis) |
| Verification | Verify signature, no lookup | Lookup the session each request |
| Revocation | Hard (valid until expiry) | Instant (delete the session) |
| Scaling | Stateless — easy across services | Needs shared session store |
| Token size | Larger (claims travel each request) | Tiny opaque ID |
When to use JWT
Stateless APIs and microservices, cross-service or third-party auth (OAuth/OIDC), and mobile clients — where avoiding a per-request session lookup is valuable. Keep token lifetimes short and pair with refresh tokens.
When to use Session
Traditional web apps and anywhere you need instant revocation and tight control — banking, admin tools — and a central session store is no burden.
Verdict
Use server sessions when you want simple, instantly-revocable auth and already have a shared store — still the safest default for many web apps. Use JWTs for stateless, distributed, or cross-domain auth, but keep them short-lived and add refresh tokens plus a revocation/denylist strategy for sensitive actions. Hybrids (short JWT access token + server-side refresh token) are common.
Common questions
Are JWTs more secure than sessions?
Not inherently — they solve different problems. Sessions are easier to revoke and keep secrets off the client; JWTs avoid per-request lookups but are hard to invalidate early. Security depends on short lifetimes, safe storage, and HTTPS more than on the choice itself.
Why are JWTs hard to revoke?
A JWT is valid until it expires because the server verifies it by signature alone, with no central record to delete. To revoke early you need extra machinery — a denylist, short expiries with refresh tokens, or token versioning — which partly reintroduces server state.