305 Use Proxy
Go through this proxy — an order browsers refused to obey.
The original HTTP/1.1, RFC 2068 of 1997, let the server tell the client to retry the request through a proxy named in Location. Network configuration delivered inside the response itself.
The idea aged badly: accepting a proxy announced in-band is an invitation to traffic hijacking. RFC 7231 explicitly deprecated it on security grounds, and browsers ignore it. It stays on the shelf as a warning — not every piece in the cabinet died of natural causes.
HTTP/1.1 305 Use Proxy
Location: http://proxy.exemplo.org:8080/
Content-Length: 0