JWT vs Session Cookies: Which to Use

JWT vs Session Cookies: Which to Use

JWT and session cookies both authenticate. Each has tradeoffs. Here is how to choose.

Session Cookies

Server stores a session (in memory or Redis) keyed by a session id. The client gets the session id in a cookie. On each request, the server looks up the session.

Pros:

• Easy to revoke (delete the session).
• Small cookie (just an id).
• No token in URL or JS.

Cons:

• Server must store sessions (memory or Redis).
• Harder to scale horizontally without a shared session store.

JWT

Server signs a token with the user id and expiry. Client stores the token (cookie or header). Server verifies the signature on each request. No session store.

Pros:

• Stateless: no session store.
• Scales horizontally easily.
• Works well for SSO and microservices.

Cons:

• Hard to revoke before expiry (no server-side session to delete).
• Larger than a session id.
• Easy to misuse (storing in LocalStorage, no expiry, etc.).

When to Use Sessions

• Single web app, no SSO, no microservices.
• You need easy revocation (delete the session).
• You want the simplest secure setup.

When to Use JWT

• Microservices (each service verifies the token independently).
• SSO across multiple apps.
• Mobile apps where you do not want a session store.
• You need stateless auth.

Common Misuses of JWT

• Storing in LocalStorage (open to XSS). Use httpOnly cookies.
• No expiry (tokens live forever). Use short expiry with refresh tokens.
• Putting sensitive data in the payload (it is base64-encoded, not encrypted). Anyone with the token can read it.
• Not validating the signature (just decoding the payload). Always use jwt.verify.

Hybrid Approach

Some apps use JWT for access (short-lived) and a refresh token (long-lived, stored in DB) to get new JWTs. Best of both worlds: stateless access, revocable refresh.

The Takeaway

Sessions are simpler and easy to revoke; use them for single web apps. JWT is stateless and scales; use it for microservices, SSO, and mobile. Avoid JWT misuses: do not store in LocalStorage, use short expiry, do not put sensitive data in the payload, always verify the signature. Hybrid: JWT access + refresh token.