505 HTTP Version Not Supported

What is HTTP 505?

This status code indicates that the server does not support or refuses to support the major version of HTTP that was used in the request message. The server is indicating that it is unable or unwilling to complete the request using the same major HTTP version as the client. This should generate a response describing why that version is not supported and what protocols the server does support.

Defined in RFC 9110

Common Causes

• The client sent a request using an HTTP version the server does not support
• An outdated server that does not support HTTP/2 or HTTP/3 receiving requests in those versions
• Misconfigured client libraries sending requests with nonstandard protocol versions

How to Fix

• Downgrade your request to an HTTP version the server supports, typically HTTP/1.1
• Update the server software if it should support newer HTTP versions
• Check your HTTP client configuration to ensure it is using a standard protocol version