Deprecating Use of the "X-" Prefix in Application Protocols

Document Type Replaced Internet-Draft (individual)
Authors Peter Saint-Andre  , Dave Crocker  , Mark Nottingham 
Last updated 2011-09-14 (latest revision 2011-07-26)
Replaced by RFC 6648
Stream (None)
Intended RFC status (None)
Expired & archived
pdf htmlized (tools) htmlized bibtex
Stream Stream state (No stream defined)
Consensus Boilerplate Unknown
RFC Editor Note (None)
IESG IESG state Replaced by draft-ietf-appsawg-xdash
Telechat date
Responsible AD (None)
Send notices to (None)

This Internet-Draft is no longer active. A copy of the expired Internet-Draft can be found at


Historically, there has often been a perceived distinction between "standard" and "non-standard" parameters (such as media types and header fields), by prefixing the latter with the string "X-" or similar constructions (e.g., "x."). In practice, this convention causes more problems than it solves. Therefore, this document deprecates the "X-" convention for most application protocol parameters.


Peter Saint-Andre (
Dave Crocker (
Mark Nottingham (

(Note: The e-mail addresses provided for the authors of this Internet-Draft may no longer be valid.)