HTTP/1.1 Error 501 - Not Implemented

This article discusses a by-design HTTP error 501 that occurs when you use an unknown method from an Internet client.

Original product version:   Internet Information Services (IIS)
Original KB number:   247643

Symptoms

When you attempt to use an unknown method from an Internet client, the following error message occurs:

HTTP/1.1 501 Not Implemented

Cause

This behavior is by design. Microsoft Internet Information Services (IIS) only supports the methods defined in RFC 2616 - Hypertext Transfer Protocol--HTTP/1.1 and RFC 2518 - HTTP Extensions for Distributed Authoring--WEBDAV. The methods are listed in the following table:

Method	Protocol	RFC	Section
CONNECT	HTTP	2616	9.9
COPY	WEBDAV	2518	8.8
DELETE	HTTP	2616	9.7
GET	HTTP	2616	9.3
HEAD	HTTP	2616	9.4
LOCK	WEBDAV	2518	8.10
MKCOL	WEBDAV	2518	8.1
MOVE	WEBDAV	2518	8.9
OPTIONS	HTTP	2616	9.2
POST	HTTP	2616	9.5
PROPFIND	WEBDAV	2518	8.1
PROPPATCH	WEBDAV	2518	8.2
PUT	HTTP	2616	9.6
TRACE	HTTP	2616	9.8
UNLOCK	WEBDAV	2518	8.11