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JWT vs. Session Tokens

A practical security comparison of JWTs and server-side session tokens for authentication.

A

JWT (JSON Web Tokens)

Pros
  • Stateless — no database lookup per request
  • Works across microservices and domains
  • Self-contained claims
  • Good for APIs and mobile apps
Cons
  • Cannot be invalidated without a denylist (stateful again)
  • Larger than a session ID
  • If secret is leaked, all tokens are compromised
  • Common security mistakes: alg:none attack, weak secrets
BEST FOR
Microservices where stateless auth is needed, third-party API access, mobile apps, short-lived tokens
B

Session Tokens (server-side)

Pros
  • Can be invalidated instantly (logout works correctly)
  • Smaller token (just an ID)
  • All session data stays on server
  • More secure by default
Cons
  • Requires server-side storage (Redis, database)
  • Harder to scale horizontally without sticky sessions or shared session store
  • Not suitable for third-party API access
BEST FOR
Traditional web apps, situations where immediate revocation is needed (admin logout, password reset), apps with strict security requirements
Verdict

For most web apps with a single backend, session tokens are simpler and more secure. Use JWTs for microservices, mobile apps, or when stateless auth is architecturally required — but use short expiry times and a token refresh strategy.

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