JWT Decoder
Paste a JSON Web Token to decode its header and payload. 100% client-side — your token never leaves the browser.
JWT Decoder decodes a JSON Web Token: shows header, payload (claims: sub, exp, iat, roles), signature. Validates structure. Runs entirely in the browser — no data sent to server, safe for production tokens.
⚠ Signature verification requires the secret key and is not performed client-side.
JWT Decoder — How It Works
A JSON Web Token (JWT) consists of three base64url-encoded parts separated by dots: Header.Payload.Signature. This tool decodes the header and payload instantly in your browser without sending the token anywhere.
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