# Constant http::header::PROXY_AUTHENTICATE [−] [src]

    pub const PROXY_AUTHENTICATE: HeaderName;

Defines the authentication method that should be used to gain access to a proxy.

Unlike `www-authenticate`, the `proxy-authenticate` header field applies only to the next outbound client on the response chain. This is because only the client that chose a given proxy is likely to have the credentials necessary for authentication. However, when multiple proxies are used within the same administrative domain, such as office and regional caching proxies within a large corporate network, it is common for credentials to be generated by the user agent and passed through the hierarchy until consumed. Hence, in such a configuration, it will appear as if Proxy-Authenticate is being forwarded because each proxy will send the same challenge set.

The `proxy-authenticate` header is sent along with a `407 Proxy Authentication Required`.