JWT & Authentication· Updated 2026-08-30· 4 min read

How to Debug an Expired JWT Token Step-by-Step

When API requests return 401 Unauthorized with token_expired, follow this sequential debugging workflow to identify whether the issue is true expiration, clock skew, or timezone offset bugs.

Step-by-Step JWT Expiration Debugging

Decode JWT Payload Claims

Launch JWT Decoder

Paste the authorization token into JWT Decoder to inspect the raw exp and iat claim values.

Tip: Verify the token has a valid 3-part structure separated by periods.

Convert exp Claim to Human-Readable Time

Launch Timestamp Explorer

Input the 10-digit exp number into Timestamp Explorer to determine the exact UTC expiration timestamp.

Tip: Ensure the server issued seconds (e.g. 1756543200) rather than JS milliseconds (1756543200000).

Check for Server Clock Skew

Compare current server UTC time with the client machine. If servers differ by more than a few seconds, configure a 30-60 second clockTolerance in your verification library.

Tip: Most JWT libraries support clockTolerance / leeway options.

Interactive Tool

JWT Decoder

Inspect Token in JWT Decoder

Inspect expiration status and remaining lifetime in JWT Decoder.

Preset Payload

eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiJ1c2VyXzEyMyIsImV4cCI6MTc1NjU0MzIwMCwiaWF0IjoxNzU2NTM5NjAwfQ.abc