BCP 47 links

This page tracks the latest versions of the drafts for the new BCP 47, which relates to language tags. These tags are commonly used in Internet protocols and referred to in W3C specifications.

The IETF Working Group responsible for this work is called the Language Tag Registry Update (or LTRU) working group. This group produced two documents to replace RFC 3066, that were published in September 2006.

RFC 4646: Tags for the Identification of Languages

Latest version

This specification describes the structure of language tags and the creation and maintenance of a registry of subtags used to form them.

RFC 4647: Matching of Language Tags

Latest version

This document describes matching and selection schemes that can be used by applications which work with language tags.

Language Subtag Registry

Hosted by IANA: http://www.iana.org/assignments/language-subtag-registry

This is the registry itself. This is currently, and for the forseeable future, the single official source of valid subtags that can be used to form language tags.

Referring to the specifications as BCP 47

It is intended that you will still be able to refer to the new specifications by the name BCP 47, and that this name will persist for all envisaged successors of these specifications. BCP 47 will refer to both of the specifications listed above.

The following URI should lead you to the new specifications once they are published by the IETF editor, however it actually points to RFC 4646:


Version: $Id: rfc3066bis.html,v 1.14 2006/09/27 11:49:26 rishida Exp $