What is a JWT (JSON Web Token)?
A JSON Web Token (JWT) is an open standard used to securely transmit information between parties as a JSON object. Because JWTs can be signed using a secret (with HMAC) or a public/private key pair (with RSA or ECDSA), the information inside can be verified and trusted. They are heavily used by developers for Authentication (letting a user log in and access specific routes) and Information Exchange.
How Does Our JWT Decoder Work?
A standard JWT consists of three parts separated by dots (.):
- 1. Header: Contains the type of the token (JWT) and the signing algorithm being used (e.g., HMAC SHA256 or RSA).
- 2. Payload: Contains the "claims" or statements about an entity (typically, the user) and additional data (like user ID, roles, or expiration time).
- 3. 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.
Our free JWT parser automatically splits these three parts, Base64Url decodes the Header and Payload, and formats them into readable JSON for easy debugging.
Security & Privacy Warning
While our JWT decoder processes your tokens 100% locally in your web browser (meaning we never send, track, or save your tokens to any server), it is a fundamental cybersecurity best practice to never paste active, production tokens containing highly sensitive secrets into any online tool. Always use test or expired tokens for debugging purposes.