Tags for Identifying Languages
RFC 4646
Document | Type |
RFC - Best Current Practice
(September 2006; Errata)
Obsoleted by RFC 5646
Obsoletes RFC 3066
|
|
---|---|---|---|
Authors | Addison Phillips , Mark Davis | ||
Last updated | 2020-01-21 | ||
Stream | IETF | ||
Formats | plain text html pdf htmlized with errata bibtex | ||
Stream | WG state | (None) | |
Document shepherd | No shepherd assigned | ||
IESG | IESG state | RFC 4646 (Best Current Practice) | |
Consensus Boilerplate | Unknown | ||
Telechat date | |||
Responsible AD | Scott Hollenbeck | ||
Send notices to | (None) |
Network Working Group A. Phillips, Ed. Request for Comments: 4646 Yahoo! Inc. BCP: 47 M. Davis, Ed. Obsoletes: 3066 Google Category: Best Current Practice September 2006 Tags for Identifying Languages Status of This Memo This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. Distribution of this memo is unlimited. Copyright Notice Copyright (C) The Internet Society (2005). Abstract This document describes the structure, content, construction, and semantics of language tags for use in cases where it is desirable to indicate the language used in an information object. It also describes how to register values for use in language tags and the creation of user-defined extensions for private interchange. This document, in combination with RFC 4647, replaces RFC 3066, which replaced RFC 1766. Phillips & Davis Best Current Practice [Page 1] RFC 4646 Tags for Identifying Languages September 2006 Table of Contents 1. Introduction ....................................................3 2. The Language Tag ................................................4 2.1. Syntax .....................................................4 2.2. Language Subtag Sources and Interpretation .................7 2.2.1. Primary Language Subtag .............................8 2.2.2. Extended Language Subtags ..........................10 2.2.3. Script Subtag ......................................11 2.2.4. Region Subtag ......................................11 2.2.5. Variant Subtags ....................................13 2.2.6. Extension Subtags ..................................14 2.2.7. Private Use Subtags ................................16 2.2.8. Preexisting RFC 3066 Registrations .................16 2.2.9. Classes of Conformance .............................17 3. Registry Format and Maintenance ................................18 3.1. Format of the IANA Language Subtag Registry ...............18 3.2. Language Subtag Reviewer ..................................24 3.3. Maintenance of the Registry ...............................24 3.4. Stability of IANA Registry Entries ........................25 3.5. Registration Procedure for Subtags ........................29 3.6. Possibilities for Registration ............................32 3.7. Extensions and Extensions Registry ........................34 3.8. Initialization of the Registries ..........................37 4. Formation and Processing of Language Tags ......................38 4.1. Choice of Language Tag ....................................38 4.2. Meaning of the Language Tag ...............................40 4.3. Length Considerations .....................................41 4.3.1. Working with Limited Buffer Sizes ..................42 4.3.2. Truncation of Language Tags ........................43 4.4. Canonicalization of Language Tags .........................44 4.5. Considerations for Private Use Subtags ....................45 5. IANA Considerations ............................................46 5.1. Language Subtag Registry ..................................46 5.2. Extensions Registry .......................................47 6. Security Considerations ........................................48 7. Character Set Considerations ...................................48 8. Changes from RFC 3066 ..........................................49 9. References .....................................................52 9.1. Normative References ......................................52 9.2. Informative References ....................................53 Appendix A. Acknowledgements ......................................55 Appendix B. Examples of Language Tags (Informative) ...............56 Phillips & Davis Best Current Practice [Page 2] RFC 4646 Tags for Identifying Languages September 2006 1. Introduction Human beings on our planet have, past and present, used a number of languages. There are many reasons why one would want to identify the language used when presenting or requesting information. A user's language preferences often need to be identified so that appropriate processing can be applied. For example, the user's language preferences in a Web browser can be used to select Web pages appropriately. Language preferences can also be used to select amongShow full document text