505
HTTP 505 HTTP Version Not Supported
5xx Server Error
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5xx Server Error
RFC 7231, Section 6.6.6
What is HTTP 505 HTTP Version Not Supported?
The 505 (HTTP Version Not Supported) status code indicates that the server does not support, or refuses to support, the major version of HTTP that was used in the request. This is rare in practice, as most servers support HTTP/1.0, HTTP/1.1, and HTTP/2.
Common Use Cases
- Legacy servers receiving unknown HTTP versions
- Restricted protocol version policies
Usage Example
If a legacy server receives an HTTP/2 request it does not support, return 505 HTTP Version Not Supported. Modern servers should support HTTP/1.0 through HTTP/2, so encountering 505 usually indicates a client or proxy configuration issue.
# Nginx - restricting HTTP versions
server {
listen 443 ssl http2;
# Only allow HTTP/2 and HTTP/1.1 by default
}