511 Network Authentication Required
The client must authenticate to the network — typically a captive portal — to gain access.
What it means
HTTP 511 Network Authentication Required means the client needs to authenticate to gain network access, rather than to access the server itself. It is meant to be returned by captive portals — the login pages on public Wi-Fi — so that software, not just humans, can recognise that a network sign-in is blocking access.
When it happens
It happens on public Wi-Fi at cafes, hotels, and airports, where a captive portal intercepts traffic until the user accepts terms or logs in.
How to fix it
- Complete the network's sign-in or captive-portal page, then retry the request.
- If you operate the portal, return 511 so clients can detect the captive state correctly.
- Confirm the device has actually joined and authenticated to the network.
SEO impact
None for your site. It comes from the network layer, not your server, so it does not affect how search engines crawl your pages.
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Related codes
A generic error meaning the server encountered an unexpected condition.
501 Not ImplementedThe server does not support the functionality required to fulfil the request.
502 Bad GatewayA server acting as a gateway received an invalid response from the upstream server.
503 Service UnavailableThe server is temporarily unable to handle the request, often due to overload or maintenance.
504 Gateway TimeoutA gateway server did not receive a timely response from the upstream server.
505 HTTP Version Not SupportedThe server does not support the HTTP protocol version used in the request.
Related guides
A plain-English primer on HTTP status codes for SEOs: what the 2xx, 3xx, 4xx, and 5xx families mean, which ones affect rankings, and the codes worth knowing.
How to find and fix broken linksA practical walkthrough for finding broken links on your site, working out why each one breaks, and fixing them so visitors and crawlers stop hitting dead ends.