JWT Decoder
Decode and analyze JSON Web Tokens (JWT) to inspect headers, payloads, and claims. Verify token structure and check expiration status for authentication debugging.
Understanding JWT (JSON Web Tokens)
JSON Web Tokens (JWT) are a compact, URL-safe means of representing claims to be transferred between two parties. They are commonly used for authentication and information exchange in web applications.
JWT Structure
A JWT consists of three parts separated by dots (.), which are: Header.Payload.Signature. Each part is Base64URL encoded.
JWT Parts Explained
Header
Contains metadata about the token, including the type of token (JWT) and the signing algorithm used (e.g., HMAC SHA256, RSA).
Payload
Contains the claims - statements about an entity (typically the user) and additional data. There are three types of claims: registered, public, and private claims.
Signature
Used to verify that the sender of the JWT is who it says it is and to ensure that the message wasn't changed along the way.
Security Considerations
While this tool helps you decode and inspect JWTs, remember that JWTs are not encrypted by default - they are only encoded. Never include sensitive information in JWT payloads unless they are encrypted. Always verify signatures in production applications.
Common Use Cases
JWTs are commonly used for user authentication, API authorization, information exchange between services, single sign-on (SSO) implementations, and stateless session management.