All HTTP status codes

HTTP 510 Not Extended

Server Error

The request must be extended (HTTP Extension Framework) for the server to fulfill it. Essentially unused on the modern web.

Defined in RFC 2774

Common causes

  • Historic HTTP extension negotiation

How to fix it

  1. Consult the service's documentation for the extension it expects

Related status codes

501 Not Implemented

The server doesn't support the functionality required — typically an HTTP method it doesn't implement at all (contrast 405: method known, not allowed here).

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