HTTP Version Not Supported
5xx Server Error
Last updated:
The server does not support the HTTP protocol version used in the request.
Description
Rarely encountered. Modern servers support HTTP/1.1 and HTTP/2 universally.
When to use
Return 505 only if you actively refuse to serve HTTP/1.0 (rare).
Specification
RFC 9110 §15.6.6
Examples
HTTP response
HTTP/1.1 505 HTTP Version Not Supported
Content-Type: application/json
{"error":"HTTP Version Not Supported"}Node.js (Express)
res.status(505).json({ error: "HTTP Version Not Supported" });Go (net/http)
w.WriteHeader(http.Status505)
Python (Flask)
return jsonify({"error": "HTTP Version Not Supported"}), 505