JWT Decoder & Debugger

What is JWT?

JWT (JSON Web Token) is an open standard (RFC 7519) for securely transmitting information between parties as a JSON object. It consists of three parts: Header, Payload, and Signature, separated by dots. JWTs are commonly used for authentication and authorization in modern web applications.

Why Use a JWT Decoder?

When developing applications with JWT authentication, you often need to inspect token contents, verify signatures, and debug authentication issues. Our JWT decoder helps you:

• •Decode and inspect JWT structure instantly
• •Verify signature with HMAC algorithms (HS256/384/512)
• •View header, payload, and signature separately
• •Check expiration time and token validity
• •Process tokens locally in your browser for maximum security

How to Use

1. Paste your JWT token into the input field
2. The tool automatically decodes and displays header and payload
3. Optionally, click 'Verify Signature' to validate the token
4. Copy decoded data with one click for further use

JWT Structure

A JWT token consists of three Base64-URL encoded parts: Header (algorithm and token type), Payload (claims and data), and Signature (cryptographic verification). The signature is created by encoding the header and payload, then signing it with a secret key using the specified algorithm.

Privacy & Security

All JWT decoding and verification happens entirely in your browser using native JavaScript and Web Crypto APIs. Your tokens and secret keys never leave your device, ensuring complete privacy and security for sensitive authentication data.