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Network Working Group                                        D. ConnollyRequest for Comments: 2854               World Wide Web Consortium (W3C)Obsoletes:2070,1980,1942,1867,1866                      L. MasinterCategory: Informational                                             AT&T                                                               June 2000The 'text/html' Media TypeStatus of this Memo   This memo provides information for the Internet community.  It does   not specify an Internet standard of any kind.  Distribution of this   memo is unlimited.Copyright Notice   Copyright (C) The Internet Society (2000).  All Rights Reserved.Abstract   This document summarizes the history of HTML development, and defines   the "text/html" MIME type by pointing to the relevant W3C   recommendations; it is intended to obsolete the previous IETF   documents defining HTML, includingRFC 1866,RFC 1867,RFC 1980,RFC1942 andRFC 2070, and to remove HTML from IETF Standards Track.   This document was prepared at the request of the W3C HTML working   group. Please send comments to www-html@w3.org, a public mailing list   with archive at <http://lists.w3.org/Archives/Public/www-html/>.1. Introduction and background   HTML has been in use in the World Wide Web information infrastructure   since 1990, and specified in various informal documents.  The   text/html media type was first officially defined by the IETF HTML   working group in 1995 in [HTML20]. Extensions to HTML were proposed   in [HTML30], [UPLOAD], [TABLES], [CLIMAPS], and [I18N].   The IETF HTML working group closed Sep 1996, and work on defining   HTML moved to the World Wide Web Consortium (W3C). The proposed   extensions were incorporated to some extent in [HTML32], and to a   larger extent in [HTML40]. The definition of multipart/form-data from   [UPLOAD] was described in [FORMDATA]. In addition, a reformulation of   HTML 4.0 in XML 1.0[XHTML1] was developed.Connolly & Masinter          Informational                      [Page 1]

RFC 2854               The 'text/html' Media Type              June 2000   [HTML32] notes "This specification defines HTML version 3.2. HTML 3.2   aims to capture recommended practice as of early '96 and as such to   be used as a replacement for HTML 2.0 (RFC 1866)."  Subsequent   specifications for HTML describe the differences in each version.   In addition to the development of standards, a wide variety of   additional extensions, restrictions, and modifications to HTML were   popularized by NCSA's Mosaic system and subsequently by the   competitive implementations of Netscape Navigator and Microsoft   Internet Explorer; these extensions are documented in numerous books   and online guides.2. Registration of MIME media type text/html   MIME media type name:      text   MIME subtype name:         html   Required parameters:       none   Optional parameters:      charset         The optional parameter "charset" refers to the character         encoding used to represent the HTML document as a sequence of         bytes. Any registered IANA charset may be used, but UTF-8 is         preferred.  Although this parameter is optional, it is strongly         recommended that it always be present. SeeSection 6 below for         a discussion of charset default rules.      Note that [HTML20] included an optional "level" parameter; in      practice, this parameter was never used and has been removed from      this specification.  [HTML30] also suggested a "version"      parameter; in practice, this parameter also was never used and has      been removed from this specification.   Encoding considerations:      SeeSection 4 of this document.   Security considerations:      SeeSection 7 of this document.   Interoperability considerations:      HTML is designed to be interoperable across the widest possible      range of platforms and devices of varying capabilities.  However,      there are contexts (platforms of limited display capability, for      example) where not all of the capabilities of the full HTML      definition are feasible. There is ongoing work to develop both a      modularization of HTML and a set of profiling capabilities to      identify and negotiate restricted (and extended) capabilities.Connolly & Masinter          Informational                      [Page 2]

RFC 2854               The 'text/html' Media Type              June 2000      Due to the long and distributed development of HTML, current      practice on the Internet includes a wide variety of HTML variants.      Implementors of text/html interpreters must be prepared to be      "bug-compatible" with popular browsers in order to work with many      HTML documents available the Internet.      Typically, different versions are distinguishable by the DOCTYPE      declaration contained within them, although the DOCTYPE      declaration itself is sometimes omitted or incorrect.   Published specification:      The text/html media type is now defined by W3C Recommendations;      the latest published version is [HTML401].  In addition, [XHTML1]      defines a profile of use of XHTML which is compatible with HTML      4.01 and which may also be labeled as text/html.   Applications which use this media type:      The first and most common application of HTML is the World Wide      Web; commonly, HTML documents contain URI references [URI] to      other documents and media to be retrieved using the HTTP protocol      [HTTP]. Many gateway applications provide HTML-based interfaces to      other underlying complex services. Numerous other applications now      also use HTML as a convenient platform-independent multimedia      document representation.   Additional information:      Magic number:         There is no single initial string that is always present for         HTML files. However,Section 5 below gives some guidelines for         recognizing HTML files.      File extension:         The file extensions 'html' or 'htm' are commonly used, but         other extensions denoting file formats for preprocessing are         also common.      Macintosh File Type code: TEXT   Person & email address to contact for further information:      Dan Connolly <connolly@w3.org>      Larry Masinter <lmm@acm.org>Connolly & Masinter          Informational                      [Page 3]

RFC 2854               The 'text/html' Media Type              June 2000   Intended usage: COMMON   Author/Change controller:      The HTML specification is a work product of the World Wide Web      Consortium's HTML Working Group.  The W3C has change control over      the HTML specification.   Further information:      HTML has a means of including, by reference via URI, additional      resources (image, video clip, applet) within the base document. In      order to transfer a complete HTML object and the included      resources in a single MIME object, the mechanisms of [MHTML] may      be used.3. Fragment Identifiers   The URI specification [URI] notes that the semantics of a fragment   identifier (part of a URI after a "#") is a property of the data   resulting from a retrieval action, and that the format and   interpretation of fragment identifiers is dependent on the media type   of the retrieval result.   For documents labeled as text/html, the fragment identifier   designates the correspondingly named element; any element may be   named with the "id" attribute, and A, APPLET, FRAME, IFRAME, IMG and   MAP elements may be named with a "name" attribute.  This is described   in detail in [HTML40]section 12.4. Encoding considerations   Because of the availability within HTML itself for using character   entity references, documents that use a wide repertoire of characters   may still be represented using the US-ASCII charset and transported   without encoding.  However, transport of text/html using a charset   other than US-ASCII may require base64 or quoted-printable encoding   for 7-bit channels.   As with all MIME text subtypes, the canonical form of "text/html"   must always represent a line break as a sequence of a CR byte value   (0x0D) followed by an LF (0x0A) byte value.  Similarly, any   occurrence of such a CRLF sequence in "text/html" must represent a   line break.  Use of CR byte values and LF byte values outside of line   break sequences is also forbidden. This rule applies regardless of   the character encoding ('charset') involved.Connolly & Masinter          Informational                      [Page 4]

RFC 2854               The 'text/html' Media Type              June 2000   Note, however, that the HTTP protocol allows the transport of data   not in canonical form, and, in particular, with other end-of-line   conventions; see [HTTP]section 3.7.1. This exception is commonly   used for HTML.   HTML sent via email is still subject to the MIME restrictions; this   is discussed fully in [MHTML]Section 10.5. Recognizing HTML files   Almost all HTML files have the string "<html" or "<HTML" near the   beginning of the file.   Documents conformant to HTML 2.0, HTML 3.2 and HTML 4.0 will start   with a DOCTYPE declaration "<!DOCTYPE HTML" near the beginning,   before the "<html". These dialects are case insensitive.  Files may   start with white space, comments (introduced by "<!--" ), or   processing instructions (introduced by "<?") prior to the DOCTYPE   declaration.   XHTML documents (optionally) start with an XML declaration which   begins with "<?xml" and are required to have a DOCTYPE declaration   "<!DOCTYPE html".6. Charset default rules   The use of an explicit charset parameter is strongly recommended.   While [MIME] specifies "The default character set, which must be   assumed in the absence of a charset parameter, is US-ASCII."  [HTTP]Section 3.7.1, defines that "media subtypes of the 'text' type are   defined to have a default charset value of 'ISO-8859-1'".Section19.3 of [HTTP] gives additional guidelines.  Using an explicit   charset parameter will help avoid confusion.   Using an explicit charset parameter also takes into account that the   overwhelming majority of deployed browsers are set to use something   else than 'ISO-8859-1' as the default; the actual default is either a   corporate character encoding or character encodings widely deployed   in a certain national or regional community. For further   considerations, please also see Section 5.2 of [HTML40].Connolly & Masinter          Informational                      [Page 5]

RFC 2854               The 'text/html' Media Type              June 20007. Security Considerations   [HTML401], section B.10, notes various security issues with   interpreting anchors and forms in HTML documents.   In addition, the introduction of scripting languages and interactive   capabilities in HTML 4.0 introduced a number of security risks   associated with the automatic execution of programs written by the   sender but interpreted by the recipient.  User agents executing such   scripts or programs must be extremely careful to insure that   untrusted software is executed in a protected environment.8. Authors' Addresses   Daniel W. Connolly   World Wide Web Consortium (W3C)   MIT Laboratory for Computer Science   545 Technology Square   Cambridge, MA 02139, U.S.A.   EMail: connolly@w3.orghttp://www.w3.org/People/Connolly/   Larry Masinter   AT&T   75 Willow Road   Menlo Park, CA 94025   EMail: LM@att.comhttp://larry.masinter.net9. References   [CLIMAPS]  Seidman, J., "A Proposed Extension to HTML: Client-Side              Image Maps",RFC 1980, August 1996.   [FORMDATA] Masinter, L., "Returning Values from Forms:              multipart/form-data",RFC 2388, August 1998.   [HTML20]   Berners-Lee, T. and D. Connolly, "Hypertext Markup              Language - 2.0",RFC 1866, November 1995.   [HTML30]   Raggett, D., "HyperText Markup Language Specification              Version 3.0", September 1995.  (Available at              <http://www.w3.org/MarkUp/html3/CoverPage>).Connolly & Masinter          Informational                      [Page 6]

RFC 2854               The 'text/html' Media Type              June 2000   [HTML32]   Raggett, D., "HTML 3.2 Reference Specification", W3C              Recomendation, January 1997.              Available at <http://www.w3.org/TR/REC-html32>.   [HTML40]   Raggett, D., et al., "HTML 4.0 Specification", W3C              Recommendation, December 1997.              Available at <http://www.w3.org/TR/1998/REC-html40-19980424>   [HTML401]  Raggett, D., et al., "HTML 4.01 Specification", W3C              Recommendation, December 1999.              Available at <http://www.w3.org/TR/html401>.   [HTTP]     Gettys, J., Fielding, R., Mogul, J., Frystyk, H.,              Masinter, L., Leach, P. and T. Berners-Lee, "Hypertext              Transfer Protocol -- HTTP/1.1",RFC 2616, June 1999.   [I18N]     Yergeau, F., Nicol, G. and M. Duerst,              "Internationalization of the Hypertext Markup Language",RFC 2070, January 1997.   [MHTML]    Palme, J., Hotmann, A. and N. Shelness, "MIME              Encapsulation of Aggregate Documents, such as HTML              (MHTML)",RFC 2557, March 1999.   [MIME]     Freed, N. and N. Borenstein, "Multipurpose Internet Mail              Extensions (MIME) Part Two: Media Types",RFC 2046,              November 1996.   [TABLES]   Raggett, D., "HTML Tables",RFC 1942, May 1996.   [UPLOAD]   Nebel, E. and L. Masinter, "Form-based File Upload in              HTML",RFC 1867, November 1995.   [URI]      Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform              Resource Identifiers (URI): Generic Syntax",RFC 2396,              August 1998.   [XHTML1]   "XHTML 1.0: The Extensible HyperText Markup Language: A              Reformulation of HTML 4 in XML 1.0", W3C Recommendation,              January 2000. Available at <http://www.w3.org/TR/xhtml1>.Connolly & Masinter          Informational                      [Page 7]

RFC 2854               The 'text/html' Media Type              June 200010. Full Copyright Statement   Copyright (C) The Internet Society (2000).  All Rights Reserved.   This document and translations of it may be copied and furnished to   others, and derivative works that comment on or otherwise explain it   or assist in its implementation may be prepared, copied, published   and distributed, in whole or in part, without restriction of any   kind, provided that the above copyright notice and this paragraph are   included on all such copies and derivative works.  However, this   document itself may not be modified in any way, such as by removing   the copyright notice or references to the Internet Society or other   Internet organizations, except as needed for the purpose of   developing Internet standards in which case the procedures for   copyrights defined in the Internet Standards process must be   followed, or as required to translate it into languages other than   English.   The limited permissions granted above are perpetual and will not be   revoked by the Internet Society or its successors or assigns.   This document and the information contained herein is provided on an   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.Acknowledgement   Funding for the RFC Editor function is currently provided by the   Internet Society.Connolly & Masinter          Informational                      [Page 8]