JWT Decoder
Paste your JWT token below to decode its header, payload, and signature instantly.
Frequently Asked Questions
What is a JSON Web Token (JWT)?
A JWT is a compact, URL-safe means of representing claims to be transferred between two parties. It's commonly used for authentication and information exchange.
What are the three parts of a JWT?
A JWT consists of three parts separated by dots (.): Header (algorithm & token type), Payload (claims), and Signature (to verify integrity).
What are 'claims' in a JWT?
Claims are statements about an entity (typically, the user) and additional data. There are registered claims (standardized), public claims, and private claims.
Are JWTs secure?
JWTs are secure when properly signed (e.g., HMAC SHA256) and optionally encrypted. The signature ensures integrity, but the payload is typically only base64 encoded, not encrypted by default.
When should I use JWTs?
JWTs are commonly used for authentication (verifying user identity) and authorization (granting access to resources) in web and mobile applications, especially in stateless architectures.
How do JWTs differ from traditional session cookies?
JWTs are stateless (server doesn't store session state), while traditional sessions store data on the server. JWTs are often stored client-side (e.g., localStorage or httpOnly cookie).
What is the purpose of the signature in a JWT?
The signature is 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.