505 HTTP Version Not Supported
505 HTTP Version Not Supported
is a status that a server can emit if
it doesn’t support the major HTTP version the client used to make the request.
To test this, I opened a telnet connection to a couple of major websites, and wrote the following:
GET / HTTP/4.0
A few sites returned a 400 Bad Request
, but at least Cloudflair returned
505
:
HTTP/1.1 505 HTTP Version Not Supported
Server: cloudflare
Date: Tue, 30 Jul 2019 15:23:35 GMT
Content-Type: text/html
Content-Length: 201
Connection: close
CF-RAY: -
<html>
<head><title>505 HTTP Version Not Supported</title></head>
<body bgcolor="white">
<center><h1>505 HTTP Version Not Supported</h1></center>
<hr><center>cloudflare</center>
</body>
</html>
Currently you’re unlikely to run into this error though, unless you have a buggy client.
We did get a new major HTTP version (2) and a new one is on the way (3), but the mechanism for switching to HTTP/2 or 3 is different, and will just be ignored if a HTTP/1.1 server didn’t support the new version.
References
- RFC7231, Section 6.6.6 - 505 HTTP Version Not Supported
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