---
title: "505 HTTP Version Not Supported — what it means and how to fix it"
description: "The server refuses to handle the version of HTTP used in the request. What causes an HTTP 505, what to try as a visitor, and what to check if it is your own site."
url: https://atoneplace.net/error/505/
site: "At One Place"
---

# 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

1. Check whether you should be using https:// rather than http:// for that address
2. Update your browser if it is very old
3. Otherwise nothing — the request is not valid HTTP as far as the server is concerned

## If it's your site

1. Check that clients are connecting to the right port with the right scheme
2. Inspect the raw request line in the access log; it usually reveals binary TLS bytes or an obviously corrupted string
3. 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](https://atoneplace.net/error/500/)
- [502 Bad Gateway](https://atoneplace.net/error/502/)
- [503 Service Unavailable](https://atoneplace.net/error/503/)
- [504 Gateway Timeout](https://atoneplace.net/error/504/)
- [524 A Timeout Occurred](https://atoneplace.net/error/524/)
- [521 Web Server Is Down](https://atoneplace.net/error/521/)
- [522 Connection Timed Out](https://atoneplace.net/error/522/)
- [520 Web Server Returned an Unknown Error](https://atoneplace.net/error/520/)
- [525 SSL Handshake Failed](https://atoneplace.net/error/525/)
- [526 Invalid SSL Certificate](https://atoneplace.net/error/526/)
- [530 Origin DNS Error](https://atoneplace.net/error/530/)
- [501 Not Implemented](https://atoneplace.net/error/501/)

## Sources

- Hypertext Transfer Protocol (HTTP) Status Code Registry — IANA (https://www.iana.org/assignments/http-status-codes/)
- RFC 9110: HTTP Semantics — IETF (https://www.rfc-editor.org/rfc/rfc9110.html)