Why this matters
Malformed or expired tokens break auth flows. This validator helps catch issues before production rollout.
What this tool does
Decode JWT header and payload locally, then validate claim timing and optional issuer/audience expectations before using the token.
Calculation model
The tool performs Base64URL decoding and JSON parsing of the token parts. Claim checks evaluate exp, nbf, and iat against current UNIX time with configurable clock skew.
Result interpretation
Read the status summary first, then inspect warnings and claim rows. A warning does not always invalidate a token, but it highlights deployment or security risk.
Limits and validation
This is a structural validator and claim checker only. It does not verify cryptographic signatures or trust chains.
Use Cases
- Validate data formats quickly while debugging APIs and integrations.
- Confirm hardware and viewport behavior during QA checks.
- Reduce context-switching by running diagnostics directly in the browser.
Frequently Asked Questions
Does this tool verify JWT signatures?
No. It validates structure and claims only. Signature verification requires algorithm-specific key validation outside this tool.
Which claims are checked automatically?
exp, nbf, and iat are checked against current time. You can also enforce expected iss and aud values.
Can I validate tokens without sending data to a server?
Yes. Decoding and validation run locally in the browser session.
Why is alg=none flagged?
alg=none disables signature verification in token design and is risky in production authorization flows.
How should I handle warnings?
Treat warnings as deployment checks. Confirm issuer, audience, clock sync, and token lifetime before accepting the token.
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