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HTTP 505 HTTP Version Not Supported
What a 505 HTTP Version Not Supported response means, why it happens, and the fastest ways to fix it.
505
HTTP Version Not Supported
5xx server error
Class
The server refuses the HTTP protocol version used in the request.
- Very old clients speaking HTTP/1.0 to strict servers, or malformed version strings from scanners.
- Use a modern client; verify intermediaries aren't mangling the request line.
Notes
HTTP status codes are defined in RFC 9110 (which replaced RFC 7231). The first digit is the class: 1xx informational, 2xx success, 3xx redirection, 4xx client error, 5xx server error.
Same class: 500 · 501 · 502 · 503 · 504 · 507
All codes: HTTP status code reference
Frequently asked questions
What does HTTP 505 mean?
HTTP 505 HTTP Version Not Supported: The server refuses the HTTP protocol version used in the request.
How do I fix a 505 error?
Use a modern client; verify intermediaries aren't mangling the request line.
Is a 505 my fault or the server's?
505 is a server error — something on the server side (or between the proxy and the app) failed.
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