What is JWT?
JWT (JSON Web Token) is an open standard that defines a compact and self-contained way of transmitting information securely between parties as a JSON object. JWTs are often used for authentication and authorization purposes, as they allow the recipient to verify the authenticity of the token and the claims contained within it.
A JWT consists of three parts: header, payload, and signature, each separated by a dot (.). The header typically consists of two parts: the type of the token, which is JWT, and the signing algorithm being used, such as HMAC SHA256 or RSA. The payload contains the claims. Claims are statements about an entity (typically, the user) and additional metadata. There are three types of claims: registered, public, and private claims. 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.
Here’s an example of a JWT:
eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4gRG9lIiwiaWF0IjoxNTE2MjM5MDIyfQ.SflKxwRJSMeKKF2QT4fwpMeJf36POk6yJV_adQssw5cIn this example, the three parts of the JWT are encoded in Base64 and separated by dots (.). To use a JWT, you need to first decode the Base64-encoded strings to get the header, payload, and signature, and then verify the signature to ensure that the token was not tampered with.
JWTs are widely used for authentication in modern web applications, as they provide a secure and efficient way to transmit information between parties. They are stateless, which means that they don’t require storage on the server, and they can be easily passed between different systems, such as a single-page app and a backend API.