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TOOL · 61 · Data & Utility

JWT Decoder

Decode a JSON Web Token's header and payload in your browser — signatures shown but never sent to a server.

In short
JWT Decoder base64url-decodes and pretty-prints a JSON Web Token's header and payload directly in your browser. Signatures are shown but never sent to any server or verified against a key.

Processed 100% in your browser — your files never leave your device.

How it works

  1. Step · 01

    Paste a JSON Web Token (JWT) into the box.

  2. Step · 02

    The header and payload are base64url-decoded and pretty-printed in your browser.

  3. Step · 03

    Signatures are shown but NOT verified — a JWT decoder never proves authenticity.

Frequently asked questions

Does this verify the JWT signature?
No — verifying a signature needs the issuer's secret or public key. This tool only decodes so you can inspect claims like sub, exp, iat and iss.
Is my token sent anywhere?
No. Decoding happens entirely in your browser with atob and JSON.parse. Nothing leaves your device.
Are my files uploaded to a server?
No. Files are processed directly in your browser using JavaScript and WebAssembly. Nothing is uploaded to our servers, so your documents never leave your device.
Does it work on mobile?
Yes. The tools run in any modern browser on desktop, tablet, or mobile (Chrome, Edge, Safari, Firefox). Very large files may be slower on low-end phones.

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