Developer ToolsFree Tool

JWT Debugger

Provided byJSON Web Token Debuggerjwt.io

Decodes, verifies, and debugs JSON Web Tokens with real-time signature validation and comprehensive language-library ...

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About this tool

What JWT Debugger does

JWT Debugger at jwt.io is a web-based utility for decoding, verifying, and generating JSON Web Tokens. Users can paste a JWT to instantly decode its header and payload, view the claims breakdown, and validate the signature using a shared secret or public key. The tool outputs the decoded JSON structures and indicates whether the signature is valid, providing a quick way to inspect token contents and ensure integrity without writing code.

Step by step

How to use the JSON Web Token Debugger JWT Debugger

  1. 1

    Paste a JWT into the decoder field

  2. 2

    View the automatically decoded header and payload JSON

  3. 3

    Enter a secret or public key to validate the signature

  4. 4

    Review the claims breakdown and signature verification result

Is it right for you

Best for

Developers and security professionals who need to quickly decode, inspect, or verify JSON Web Tokens during debugging or integration testing.

Limitations

  • Signature validation requires knowledge of the signing secret
  • No built-in support for token generation from scratch without manual JSON assembly
  • Interface is functional but minimal, lacking advanced parsing filters
Questions

JWT Debugger FAQ

Can I use this tool to create a new JWT from scratch?
The page includes an encoder that lets you generate a JWT by providing a header and claims payload, which the tool then signs and encodes for you.
What happens if I paste an invalid JWT format?
The decoder will typically return an error or fail to parse the token, as it expects the standard three-part base64url structure separated by periods.
Is the signature verification step required to decode a token?
No, the header and payload are decoded automatically upon pasting a JWT; signature verification is optional and requires the matching secret or key.
Does the tool support different signing algorithms?
The interface includes algorithm selection (such as HS256) and fields for entering the corresponding secret or key material to match the chosen method.
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