status Registered
Verified 2026-09-18 · registry updated 2025-09-15

HTTP 505 HTTP Version Not Supported

The server does not support the HTTP version used in the request.

Use 505 when protocol-version negotiation cannot satisfy the client request.

httpstatus codeprotocol

Response (http)

HTTP/1.1 505 HTTP Version Not Supported

Use 505 when protocol-version negotiation cannot satisfy the client request.

Common mistakes

  • Rejecting a major version the server could support through normal negotiation.

Registry reference: RFC9110, Section 15.6.6

Sources

Permalink: https://merginit.com/reference/http/status-505