How does HTTP Authentication work?

HTTP authentication requires a client (such as a web browser or an API client) to provide credentials before accessing a protected resource on a server. There are two common methods: Basic Authentication and Digest Authentication.

Basic Authentication: The client sends a username and password, encoded in Base64, as part of the HTTP headers. The server checks the credentials and either grants access or responds with a 401 Unauthorized status if they are invalid. This method should be used with HTTPS to prevent credential exposure.

Digest Authentication: This method improves security by sending a hashed version of the username, password, and additional data (like a server-generated nonce) instead of plain credentials. The server verifies the hash before granting access.

In both cases, the server responds with a challenge if the client fails to provide the necessary credentials, and the client must reattempt with the correct information to access the resource.