JWT Token Validation Fails - Invalid Signature or Expiration
API requests fail with JWT verification errors even though the token appears valid. Tokens work initially but fail after some time or across different server instances.
Symptoms include immediate '401 Unauthorized' on API calls, 'JsonWebTokenError: invalid signature', or tokens expiring immediately after issue.
Error Messages You Might See
Common Causes
- Secret key mismatch between token creation and verification
- JWT expires too quickly or has wrong expiration time
- Token created with different secret than verification uses
- Multiple server instances using different secrets
- Clock skew between client and server causing 'not yet valid' errors
How to Fix It
Store JWT secret in environment variable and use identical value for both signing and verification
Set reasonable expiration: 15min for access token, 7d for refresh token
Implement token refresh: when access token expires, use refresh token to get new one without user re-logging in
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Get HelpFrequently Asked Questions
What's a good JWT expiration time?
Access tokens: 15 minutes. Refresh tokens: 7 days. This balances security with user experience
How do I implement token refresh?
Store refresh token in secure httpOnly cookie. When access token expires, send refresh token to /api/refresh endpoint to get new access token
Why does my token fail on different servers?
Ensure all server instances use the same JWT secret from environment variables