What are API authentication best practices?

Here are the main API authentication best practices:

1. Use strong, modern auth methods

   • Prefer OAuth 2.0 / OpenID Connect for user-facing apps.
   • Use short-lived access tokens and refresh tokens when appropriate.
   • For service-to-service auth, use mTLS, signed JWTs, or client credentials.

2. Never send credentials in plaintext

   • Always use HTTPS/TLS.
   • Reject non-TLS traffic.

3. Use least privilege

   • Give each client only the minimum scopes/permissions needed.
   • Separate credentials by app, environment, and role.

4. Keep tokens short-lived

   • Short expiration reduces damage if a token is stolen.
   • Rotate refresh tokens and revoke them when suspicious activity is detected.

5. Store secrets securely

   • Use a secret manager or vault, not source code or config files.
   • Never hardcode API keys in frontend apps or public repos.

6. Rotate and revoke credentials

   • Support key rotation without downtime.
   • Provide a way to revoke compromised tokens/keys immediately.

7. Validate tokens properly

   • Check signature, issuer, audience, expiration, and not-before claims.
   • Do not accept unsigned or weakly signed tokens.

8. Protect against replay and abuse

   • Use nonces, timestamps, or one-time tokens where needed.
   • Rate limit authentication endpoints and sensitive APIs.
   • Add anomaly detection for unusual login/API usage patterns.

9. Use secure session handling

   • If using cookies, set HttpOnly, Secure, and SameSite.
   • Prefer stateless tokens only when appropriate; avoid long-lived bearer tokens if possible.

10. Log carefully

    • Log auth events, failures, and token issuance/rotation.
    • Never log secrets, full tokens, passwords, or sensitive claims.

11. Support MFA for interactive users

    • Especially for admin accounts and privileged actions.

12. Design for key separation

    • Different keys for dev/staging/prod.
    • Distinguish machine, user, and admin credentials.

13. Be cautious with API keys

    • API keys identify the caller, but often do not provide strong authentication by themselves.
    • Combine them with other controls if used at all.

14. Follow standards

    • Use proven libraries and standards instead of custom cryptography or bespoke auth schemes.

If you want, I can also give you:

• a checklist for REST APIs
• best practices for JWT
• best practices for API keys vs OAuth
• a production security checklist for APIs