JWT Decoder & Debugger
A JWT decoder splits a JSON Web Token into its three color-coded segments: Header, Payload, and Signature. It decodes claims, issuer, subject, scopes, and expiration timestamps safely in your browser without transmitting your token over the internet.
How to Use JWT Decoder & Debugger
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Paste Token: Paste your encoded JWT token (header.payload.signature) into the input box.
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Inspect Header: Review algorithm (alg), token type (typ), and key ID (kid) parameters.
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Analyze Claims: Inspect user ID, roles, scopes, issuer (iss), audience (aud), and custom claims.
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Check Expiry: View human-readable issued-at (iat) and expiration (exp) timestamps with active/expired status.
Frequently Asked Questions
- Is it safe to paste private JWT tokens here?
- Yes. Unlike some online decoders that send tokens to a server, FronzaTools decodes JWTs purely using client-side JavaScript in your browser.
- What does Token Expired mean?
- When the exp claim epoch timestamp is earlier than the current time, the token is no longer valid and the user must refresh their session.
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