JWT Debugger (JSON Web Token Insight)

Free online JWT debugger.
Decode JSON Web Tokens (Auth0 standard) in real-time and verify signatures.
Instantly convert expiration (exp) and issued-at (iat) times into human-readable dates.

Security Note: All token decoding is performed locally within your browser's environment. Your tokens are never transmitted to our servers or exposed externally, ensuring total privacy.
Header (Algorithm & Token Type)ALGORITHM & TOKEN TYPE
// Header content
Payload (Data & Claims)DATA
// Payload content
Signature (Verify Sign)VERIFICATION
HMACSHA256( base64UrlEncode(header) + "." + base64UrlEncode(payload), your-256-bit-secret )

Why Use Today Lab JWT Debugger?

  • ✓Real-time JSON visualization of Header and Payload
  • ✓Automatic conversion of UNIX timestamps (exp, iat, nbf) to dates
  • ✓Maximum security via local processing in browser sandbox
  • ✓Enhanced readability for complex signature structures

Debugger Usage Guide

  1. 1

    Paste the 'Encoded' string you wish to analyze into the left pane.

  2. 2

    Review the interpreted header and payload content on the right in real-time.

  3. 3

    Specifically check the 'exp' field for human-readable dates to verify token expiration.

  4. 4

    Use the 'Clean' button after debugging to easily clear the entered data.

Learn More

What exactly is a JSON Web Token (JWT)?

JWT is an open standard (RFC 7519) for securely transmitting information between two parties as a JSON object. It is designed to be compact and self-contained, commonly used for authentication and information exchange in modern web applications.

Why is JWT essential in modern web development?

JWTs are highly scalable because they eliminate the need for servers to store session state. In microservice architectures, each server can independently verify permissions, significantly reducing server load. They are also the most compatible authentication method between mobile apps and browsers.

The Three Structures and Working Principles of JWT

A JWT consists of three parts separated by dots (.):
1. Header: Defines the token type and encryption algorithm.
2. Payload: Contains the actual data (claims) such as User ID and expiration time.
3. Signature: A digital signature created by the server using a secret key to verify the token has not been tampered with.