Unauthorized

The 401 Unauthorized HTTP status code is issued in response to requests that require user authentication. Unlike the 403 Forbidden status code, which we'll discuss later, 401 Unauthorized does not necessarily mean that the request will not be allowed under any circumstances. Instead, it implies that the request could be accepted if it had valid authentication credentials. If the request already included credentials, then the 401 response indicates that authorization has been refused for those credentials. When a server returns a 401 Unauthorized status, it must also send a WWW-Authenticate header field, indicating the authentication scheme and realm applicable to the requested resource. This status is crucial for implementing access control to sensitive resources and is a fundamental part of web security.