HTTP 505 HTTP Version Not Supported

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

# Nginx - restricting HTTP versions
server {
    listen 443 ssl http2;
    # Only allow HTTP/2 and HTTP/1.1 by default
}