JWT (short for "JSON Web Token") is a standard for representing and transmitting secure, digitally-signed JSON-based data between parties. JWTs are commonly used as a means of authentication and authorization in web applications and APIs.
A JWT is comprised of three parts: a header, a payload, and a signature. The header specifies the algorithm used to sign the token, as well as the type of token. The payload contains the claims or assertions being made by the token, such as the user ID or the expiration time. The signature is generated using a secret key and is used to verify the authenticity of the token.
When a user logs in to a web application, the server generates a JWT and sends it back to the client. The client then stores the JWT, usually in a cookie or in local storage, and includes it in subsequent requests to the server. The server can then verify the JWT and use the claims in the payload to identify the user and authorize access to resources.
One of the advantages of JWTs is that they are self-contained, meaning that all of the necessary information is contained within the token itself. This makes them very convenient for use in stateless applications, where the server does not need to maintain any session state. However, JWTs do have some security considerations, such as ensuring that the secret key used to sign the token is kept secure and that the token is transmitted over a secure channel.