This API lets websites interact with a user agent's password system directly so that websites can deal in a uniform way with site credentials and user agents can provide better assistance with the management of their credentials. For example, user agents have a particularly hard time dealing with federated identity providers or esoteric sign-in mechanisms.
To address these problems, the Credential Management API provides ways for a website to store and retrieve different types of credentials. This gives users capabilities such as seeing the federated account they used to sign on to a site, or resuming a session without the explicit sign-in flow of an expired session.