What are the security best practices for handling JWT tokens?

Keep no secrets in the payload (it's only Base64, not encrypted), reject alg: none, keep tokens short-lived (plus a logout/blacklist strategy), and use a vetted JWT library.

1. Protect sensitive information

   • Payload is only Base64 encoded, NOT encrypted
   • Don't put secrets in the payload

2. Ensure algorithm "None" is not accepted

   • Attackers can forge tokens by setting alg: "none"
   • Always validate the algorithm server-side

3. Implement logout

   • Use token blacklists or short expiration
   • JWTs are stateless, so logout is harder than sessions

4. Limit validity time

   • Short-lived access tokens (minutes)
   • Longer refresh tokens with rotation

5. Use a JWT library

   • Don't implement JWT parsing/validation yourself
   • Libraries handle edge cases and vulnerabilities

See: OWASP JWT Cheat Sheet | jwt.io — decode and inspect JWT tokens

Go deeper:

• PortSwigger — JWT attacks — shows why the rules matter: signature bypass, alg:none, key brute-force, algorithm confusion, with labs.