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 |