DevFmt/

JWT Decoder

Input — JWT
Output — Decoded

How to use JWT Decoder

JWT Decoder splits a JSON Web Token into its three parts — header, payload, and signature — and decodes the Base64url-encoded header and payload into readable JSON. Paste a token and instantly inspect its claims: who issued it, who it's for, when it was issued, and when it expires.

The decoder also surfaces useful derived information such as the token's expiration status and human-readable issued-at and expiry times, so you can quickly tell whether a token is still valid.

Key features: decodes header and payload to formatted JSON, shows the signature segment, highlights expiration status, converts iat/exp timestamps to readable dates, and runs entirely client-side.

Important: this tool decodes tokens only — it does not verify the signature. Decoding reveals what a JWT contains, but it does not prove the token is authentic. Never trust a token's claims without verifying its signature on a server using the secret or public key. Because decoding happens entirely in your browser, you can safely inspect tokens that contain sensitive claims — nothing is sent to or logged by any server.

FAQ

How do I decode a JWT?
Paste the token (three Base64url segments separated by dots) into the input panel. DevFmt decodes the header and payload into readable JSON and shows the expiration status.
Does this verify the token's signature?
No. This tool only decodes the token to show its contents. It does not verify the signature, so it can't confirm the token is authentic. Always verify signatures server-side before trusting a token.
Is it safe to paste a real token here?
Yes. Decoding happens entirely in your browser — the token is never sent to a server. That said, treat production tokens carefully and avoid sharing screenshots that expose them.
What do iat and exp mean?
iat is 'issued at' and exp is 'expiration' — both are Unix timestamps. The decoder converts them to readable dates and flags whether the token has expired.

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