HTTP 505 — HTTP Version Not Supported
HTTP 505
HTTP Version Not Supported
The server refuses to handle the version of HTTP used in the request.
What 505 actually means
The major HTTP version in the request line is one the server will not serve. It is rare, because version negotiation normally happens transparently and servers accept anything from HTTP/1.0 upwards. When it does appear it usually means something is not speaking HTTP at all — a garbled request from a misconfigured client, or a raw TLS handshake arriving on a plaintext port and being parsed as a nonsensical version string.
Common causes
- A malformed request line that the server parses as an unknown version
- An HTTPS request sent to a port serving plain HTTP
- A very old or hand-rolled client using an unsupported version
- A proxy mangling the request line
If you're just trying to view the page
- Check whether you should be using https:// rather than http:// for that address
- Update your browser if it is very old
- Otherwise nothing — the request is not valid HTTP as far as the server is concerned
If it's your site
- Check that clients are connecting to the right port with the right scheme
- Inspect the raw request line in the access log; it usually reveals binary TLS bytes or an obviously corrupted string
- The response must state which versions are supported, so include that
Reference
- Status code
- 505
- Reason phrase
- HTTP Version Not Supported
- Category
- 5xx — Server Error
- Cacheable by default
- No
- Defined in
- RFC 9110 §15.6.6
Common questions
- What does HTTP 505 mean?
- The server refuses to handle the version of HTTP used in the request. The major HTTP version in the request line is one the server will not serve. It is rare, because version negotiation normally happens transparently and servers accept anything from HTTP/1.0 upwards.
- How do I fix a 505 error?
- Check whether you should be using https:// rather than http:// for that address
- Is 505 a client error or a server error?
- 505 is in the 5xx range, which means server error. The request was acceptable but the server could not fulfil it, so retrying later can succeed.
Related pages
- 500 Internal Server Error Something went wrong on the server and it has no more specific code to describe
- 502 Bad Gateway A proxy or gateway reached the server behind it and got back a broken response,
- 503 Service Unavailable The server is temporarily unable to handle the request, usually because it is ov
- 504 Gateway Timeout A proxy or gateway waited for the server behind it and gave up before an answer
- 524 A Timeout Occurred Cloudflare connected to the origin successfully but the origin did not finish re
- 521 Web Server Is Down Cloudflare could not connect to the origin server because it refused the connect
- 522 Connection Timed Out Cloudflare tried to open a connection to the origin server and never got a reply
- 520 Web Server Returned an Unknown Error Cloudflare reached the origin server but got back a response it could not make s
- 525 SSL Handshake Failed The TLS handshake between Cloudflare and the origin server failed.
- 526 Invalid SSL Certificate The origin server presented a TLS certificate that Cloudflare could not validate
- 530 Origin DNS Error A Cloudflare error shown alongside a 1xxx error code that carries the real expla
- 501 Not Implemented The server does not support the functionality needed to fulfil the request, usua