RFC 2279 (rfc2279) - Page 1 of 10

UTF-8, a transformation format of ISO 10646

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Network Working Group                                       F. Yergeau
Request for Comments: 2279                           Alis Technologies
Obsoletes: 2044                                           January 1998
Category: Standards Track


              UTF-8, a transformation format of ISO 10646

Status of this Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (1998).  All Rights Reserved.

Abstract

   ISO/IEC 10646-1 defines a multi-octet character set called the
   Universal Character Set (UCS) which encompasses most of the world's
   writing systems. Multi-octet characters, however, are not compatible
   with many current applications and protocols, and this has led to the
   development of a few so-called UCS transformation formats (UTF), each
   with different characteristics.  UTF-8, the object of this memo, has
   the characteristic of preserving the full US-ASCII range, providing
   compatibility with file systems, parsers and other software that rely
   on US-ASCII values but are transparent to other values. This memo
   updates and replaces RFC 2044, in particular addressing the question
   of versions of the relevant standards.

1.  Introduction

   ISO/IEC 10646-1 [ISO-10646] defines a multi-octet character set
   called the Universal Character Set (UCS), which encompasses most of
   the world's writing systems.  Two multi-octet encodings are defined,
   a four-octet per character encoding called UCS-4 and a two-octet per
   character encoding called UCS-2, able to address only the first 64K
   characters of the UCS (the Basic Multilingual Plane, BMP), outside of
   which there are currently no assignments.

   It is noteworthy that the same set of characters is defined by the
   Unicode standard [UNICODE], which further defines additional
   character properties and other application details of great interest
   to implementors, but does not have the UCS-4 encoding.  Up to the



Yergeau                     Standards Track
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