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JWT decoder

Paste a JWT and read its header and payload side by side, with the registered claims labeled and exp/nbf/iat shown as local date-times with expiry badges. For HS256/384/512 a secret field verifies the signature locally via WebCrypto.

Privacy ledger

Data acquired None.
Libraries used Lit 3 — bundled into the tool file itself.
Data stored None.
Data transmitted None.

Use it on your own page

Download the tool as a single self-contained HTML file: readable source with the Lit library included, zero network requests — it works opened straight from your disk, and you can customize everything.

Prefer the hosted widget? One script tag embeds it and stays up to date:

<script type="module" src="https://uuutil.com/tools/jwt-decoder.js"></script>
<uu-jwt-decoder lang="en"></uu-jwt-decoder>

Source license: MIT — free to use, modify and redistribute; keep the license notice in copies.