HTTP 511 Network Authentication Required

Server error code, RFC 6585

What it means

You must log in to the network before you can use the internet, as at a hotel or airport Wi-Fi sign-in page.

A real response

This is the request and the answer our test server gave when we asked it to return 511.

GET /c/511 HTTP/1.1
Host: example.com

HTTP/1.1 511 Network Authentication Required
Date: Sat, 14 Nov 2026 10:00:00 GMT
Content-Type: text/html; charset=utf-8
Content-Length: 11

<p>demo</p>

If you run the site

RFC 6585 describes 511 for networks that intercept traffic with a login page. It is sent by the network, not by the site you wanted to reach. Interception pages that send 200 instead can make apps believe they are online.

If you are a visitor

Open a normal website over http (for example neverssl.com) so that the sign-in page appears, then log in.

A common mistake

Reporting it as a problem of the website you were trying to open.

Registered in the IANA HTTP Status Code Registry as Network Authentication Required, defined in RFC 6585.

This is an independent guide. It is not connected with the IETF, IANA, any browser maker or any company named here. Meanings were checked against the RFC texts on 14 November 2026. Responses shown were recorded on 14 November 2026 from a small test server on the author's own computer.