JWT Decoder
Decode and verify JSON Web Tokens. View header, payload, and signature information. Check token expiration status. All processing happens locally in your browser.
About JWT Decoder
Decode and inspect JSON Web Tokens (JWT) with our free online tool. JWTs are commonly used for authentication and information exchange in modern web applications. This tool helps developers debug and verify JWT tokens by decoding the Base64Url-encoded header and payload sections.
How to Use
- Paste your JWT token in the input field above.
- Click Decode JWT to parse the token.
- View the Header section to see the algorithm and token type.
- View the Payload section to see the claims and data.
- Check the expiration status indicator above the output sections.
- Use the Copy buttons to copy decoded sections.
- Click Load Sample to see an example JWT token.
Frequently Asked Questions
What is a JWT token?
JSON Web Token (JWT) is an open standard (RFC 7519) for securely transmitting information between parties as a JSON object. JWTs are commonly used for authentication and authorization in web applications. They consist of three parts: header, payload, and signature, separated by dots.
Can this tool verify JWT signatures?
This tool decodes the header and payload for inspection but cannot verify the signature without the secret key or public key. Signature verification requires the key that was used to sign the token, which should remain secret. You can see the signature structure, but validation requires server-side implementation.
What does the expiration check do?
The expiration check looks at the "exp" (expiration time) claim in the payload and compares it to the current time. If the token has expired, you'll see a warning. This is useful for debugging authentication issues related to expired tokens.
Is my JWT token safe when using this tool?
Yes. All processing happens entirely within your browser. Your JWT tokens are never transmitted to any server or stored anywhere. However, be cautious when handling JWTs in shared environments, as they may contain sensitive information.
What are common JWT claims?
Common JWT claims include: "sub" (subject/user ID), "iss" (issuer), "aud" (audience), "exp" (expiration time), "iat" (issued at), "nbf" (not before), and "jti" (JWT ID). Custom claims can also be added depending on the application's needs.