JWT

JSON Web Tokens (JWT) are a popular standard for creating access tokens that assert some number of claims. They are a cornerstone of modern stateless authentication, especially for APIs and Single-Page Applications. A JWT consists of three parts separated by dots: the Header, the Payload, and the Signature. 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 data. There are registered claims (like `iss` for issuer, `exp` for expiration time), public claims, and private claims. For example, you would include the user's ID and role in the payload. 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. It is created by taking the encoded header, the encoded payload, a secret key, and the algorithm specified in the header and signing that. The main advantage of JWT is that it is stateless. The server does not need to store any information about the user's session. The token itself contains all the necessary information. When the client makes a request to a protected route, it sends the JWT in the `Authorization` header. The server then validates the signature. If it's valid, the server can trust the information in the payload and authorize the request.