12. Use of HTTP Status Codes

These HTTP codes are not redefined, but their use is somewhat extended by WebDAV methods and requirements. In general, many HTTP status codes can be used in response to any request, not just in cases described in this document. Note also that WebDAV servers are known to use 300-level redirect responses (and early interoperability tests found clients unprepared to see those responses). A 300-level response MUST NOT be used when the server has created a new resource in response to the request.

12.1. 412 Precondition Failed

Any request can contain a conditional header defined in HTTP (If-Match, If-Modified-Since, etc.) or the "If" or "Overwrite" conditional headers defined in this specification. If the server evaluates a conditional header, and if that condition fails to hold, then this error code MUST be returned. On the other hand, if the client did not include a conditional header in the request, then the server MUST NOT use this status code.

12.2. 414 Request-URI Too Long

This status code is used in HTTP 1.1 only for Request-URIs, not URIs in other locations.