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Free JWT Decoder Online

Developer Tools

What is Free JWT Decoder Online?

JWT Decoder is a browser-based tool for inspecting JSON Web Tokens without sending them to any server. JWTs are a common authentication mechanism in modern web applications - they encode identity claims, permissions, and session data in a signed, URL-safe string. A JWT consists of three parts: a header (algorithm), a payload (claims), and a signature. This tool decodes the header and payload so you can read the contents instantly, while keeping your token entirely on your device.

How it works

JWTs use Base64URL encoding, which replaces + with - and / with _. The three parts are separated by dots. This tool splits the string, decodes each part from Base64URL, and formats the result as readable JSON. Signature verification is NOT performed - that requires the secret key and would need to be done server-side.

Features & Benefits

  • Decodes entirely in your browser - your token never leaves your device
  • This is critical for JWTs: pasting tokens into online tools that use servers is a security risk
  • Shows expiry time (exp claim) as a human-readable date with expired/valid status
  • Formats header and payload as prettified JSON for easy reading

Frequently Asked Questions

Does this verify the JWT signature?

No. This tool decodes the header and payload only. Signature verification requires your secret key and would need to be done server-side.

Why is it important to use a browser-based JWT decoder?

JWTs often contain sensitive data like user IDs, roles, and permissions. Pasting them into a tool that sends data to a server exposes that data. This tool processes everything locally.

What does 'signature present' mean?

It means the JWT has three parts (header.payload.signature), which is a standard signed JWT. A JWT with only two parts (no signature) is unsecured.

Can I decode expired JWTs?

Yes. The decoder works on any valid JWT structure regardless of expiry. The tool will show the expiry status clearly.

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