JSON Web Tokens enable stateless authentication by encoding claims in signed tokens. Proper implementation requires understanding security considerations and token lifecycle management.
Token Structure
JWTs contain header, payload, and signature. Headers specify algorithm. Payloads contain claims—standard and custom. Signatures prevent tampering. Validate all parts on receipt.
- Use strong signing algorithms like RS256 or ES256
- Include expiration claims limiting token lifetime
- Avoid storing sensitive data in payloads
- Implement token refresh for long sessions
- Validate tokens completely on every request
Security Patterns
Short expiration reduces exposure from leaked tokens. Refresh tokens enable re-authentication. Token revocation requires additional infrastructure. Consider session cookies for simpler security needs.