Webmaster in a Nutshell, Third Edition

Name

WWW-Authenticate

Synopsis

                        WWW-Authenticate: scheme 
                        realm
                     

Used with the 401 (Unauthorized) response code. It specifies the authorization scheme and realm of authorization required from a client at the requested URI. Many different authorization realms can exist on a server. A common authorization scheme is BASIC, which requires a username and password. For example:

WWW-Authenticate: BASIC realm="Admin"

When returned to the client, this header indicates that the BASIC type of authorization data in the appropriate realm should be returned in the client’s Authorization header.