JWT Expiration Checker
Decode and inspect JWT tokens client-side. View header, payload, and signature. Detect expiration, iat, and nbf claims. Compute time-until-expiry with live countdown.
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Applications
Inspect JWT tokens from auth servers, debug OAuth flows, verify token expiration without sending credentials over the network, and check if stored tokens are still valid before making API calls.
How It Works
JWTs are Base64URL-encoded and signed with a secret. This tool decodes the header and payload in the browser using atob() and TextDecoder, extracts standard claims, and computes time remaining until expiration. No data is sent to any server.
Fun Fact: JWTs are stateless - the server does not need to query a database to validate them. As long as you have the secret or public key, you can verify the signature and read the payload locally.
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