511 Network Authentication Required (RFC 6585)
This is an educational reference page about HTTP 511 Network Authentication Required. The page itself is served as 200 OK so it can be indexed as HTTP documentation.
The client needs to authenticate to gain network access. Intended for use by intercepting proxies used to control access to the network (e.g., "captive portals" used to require agreement to Terms of Service before granting full Internet access via a Wi-Fi hotspot).