505 HTTP Version Not Supported
The server does not support the HTTP protocol version used in the request.
What it means
HTTP 505 HTTP Version Not Supported means the server refuses to handle the HTTP version the client used. Either the version is too old for the server to accept, or it is one the server was never built to speak.
When it happens
It happens with malformed requests that declare an invalid HTTP version, very old clients speaking a version the server has dropped, or a misconfiguration in how the server negotiates protocol versions.
How to fix it
- Have the client use a standard, supported HTTP version such as HTTP/1.1 or HTTP/2.
- Update an outdated client or library that is sending an unsupported version.
- Check the server and any proxy for misconfigured protocol-version handling.
SEO impact
Negative if it affects real pages, but rare. Crawlers use standard HTTP versions, so this seldom blocks them; if it does, the page cannot be indexed.
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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.
506 Variant Also NegotiatesA server misconfiguration in content negotiation causes an internal negotiation loop.
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.