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Web Encodings
My scratchpad for encoding related notes.
Goals
- Document existing practices by describing for each browser
- The list of supported encodings.
- The list of supported labels for those encodings.
- The matching algorithm for labels.
- Converge the various used algorithms by
- Defining a list of encodings everyone has to support. Browsers may not support more encodings than on that list.
- Defining a list of supported labels for those encodings. Browsers may not support more labels than on that list.
- Defining the matching algorithm. (HTML5 has been updated with a better one now.)
- Get the new rules implemented
Documenting more exactly the encoding and decoding algorithms for each encoding and getting that implemented interoperably would also be great.
Current Implementations
Does this differ per platform? Opera might differ a bit on Mac.
Data
Integrate this awesome data somehow:
- http://coq.no/character-tables/mime/en
- http://coq.no/character-tables/mime/iso-2022/en
- http://coq.no/character-tables/mime/euc/en
- http://coq.no/character-tables/mime/locale-specific/en
Opera
Matching
UTS22 and strips leading x characters. (For now, plan is to switch to removing leading and trailing whitespace and ASCII case-insensitive matching afterwards in the future.)
Encodings
| Encoding | Labels | Decoded As | Notes |
|---|---|---|---|
| big5 | big5, cnbig5, csbig5 | ||
| big5-hkscs | big5hkscs | ||
| euc-jp | cseucpkdfmtjapanese, eucjp, extendedunixcodepackedformatforjapanese | ||
| euc-kr | cseuckr, csksc56011987, euckr, isoir149, korean, ksc5601, ksc56011987, ksc56011989, windows949 | ||
| euc-tw | euctw | ||
| gb18030 | gb18030 | ||
| gbk | chinese, cngb, cp936, csgb2312, csiso58gb231280, euccn, gb2312, gb231280, gbk, isoir58, ms936, windows936 | ||
| hz-gb-2312 | hzgb2312 | ||
| ibm866 | 866, cp866, csibm866, ibm866 | ||
| iso-2022-cn | iso2022cn | ||
| iso-2022-jp | csiso2022jp, iso2022jp | ||
| iso-2022-jp-1 | iso2022jp1 | ||
| iso-2022-kr | csiso2022kr, iso2022kr | ||
| iso-8859-1 | cp819, csisolatin1, ibm819, iso88591, iso885911987, isoir100, l1, latin1 | windows-1252 | |
| iso-8859-2 | csisolatin2, iso88592, iso885921987, isoir101, l2, latin2 | ||
| iso-8859-3 | csisolatin3, iso88593, iso885931988, isoir109, l3, latin3 | ||
| iso-8859-4 | csisolatin4, iso88594, iso885941988, isoir110, l4, latin4 | ||
| iso-8859-5 | csisolatincyrillic, cyrillic, iso88595, iso885951988, isoir144 | ||
| iso-8859-6 | arabic, asmo708, csiso88596e, csisolatinarabic, ecma114, iso88596, iso885961987, iso88596e, isoir127 | ||
| iso-8859-6-i | csiso88596i, iso88596i | ||
| iso-8859-7 | csisolatingreek, ecma118, elot928, greek, greek8, iso88597, iso885971987, isoir126 | ||
| iso-8859-8 | csiso88598e, csisolatinhebrew, hebrew, iso88598, iso885981988, iso88598e, isoir138, visual | ||
| iso-8859-8-i | csiso88598i, iso88598i | ||
| iso-8859-9 | csisolatin5, iso88599, iso885991989, isoir148, l5, latin5 | ||
| iso-8859-10 | csisolatin6, iso885910, iso8859101992, isoir157, l6, latin6 | ||
| iso-8859-11 | iso885911, tis620, tis6202533, windows874 | Actually implemented as windows-874 | |
| iso-8859-13 | iso885913 | ||
| iso-8859-14 | iso885914, iso8859141998, isoceltic, isoir199, l8, latin8 | ||
| iso-8859-15 | iso885915, latin9 | ||
| iso-8859-16 | iso885916, iso8859162001, isoir226, l10, latin10 | ||
| koi8-r | cskoi8r, koi8r | ||
| koi8-u | koi8u | ||
| macintosh | csmacintosh, mac, macintosh, macroman | Likely disabled. | |
| shift_jis | cp932, csshiftjis, cswindows31j, ms932, mskanji, shiftjis, sjis, windows31j | ||
| tcvn | tcvn, viettcvn | ||
| us-ascii | ansix341968, ansix341986, ascii, cp367, csascii, csinvariant, csiso646basic1983, ibm367, invariant, iso646basic1983, iso646irv1991, iso646us, isoir6, ref, us, usascii | windows-1252 | |
| utf-16 | csunicode, csunicode11, csunicodeascii, iso10646j1, iso10646ucs2, iso10646ucsbasic, utf16 | ||
| utf-16be | utf16be | ||
| utf-16le | utf16le | ||
| utf-8 | utf8 | ||
| viscii | csviscii, viscii | ||
| windows-1250 | cp1250, microsoftcp1250, windows1250 | ||
| windows-1251 | cp1251, microsoftcp1251, windows1251 | ||
| windows-1252 | cp1252, microsoftcp1252, windows1252 | ||
| windows-1253 | cp1253, microsoftcp1253, windows1253 | ||
| windows-1254 | cp1254, microsoftcp1254, windows1254 | ||
| windows-1255 | cp1255, microsoftcp1255, windows1255 | ||
| windows-1256 | cp1256, microsoftcp1256, windows1256 | ||
| windows-1257 | cp1257, microsoftcp1257, windows1257 | ||
| windows-1258 | cp1258, microsoftcp1258, windows1258 | ||
| windows-sami-2 | samiws2, windowssami2, ws2 | ||
| x-mac-ce | macce | Likely disabled. | |
| x-mac-cyrillic | maccyrillic | Likely disabled. | |
| x-mac-greek | macgreek | Likely disabled. | |
| x-mac-turkish | macturkish | Likely disabled. | |
| x-vps | vps |
Firefox
Matching
ASCII lowercasing.
Encodings
| Encoding | Labels | Decoded As | Notes |
|---|---|---|---|
| armscii-8 | armscii-8 | ||
| Big5 | big5, csbig5, x-x-big5, zh_tw-big5 | ||
| Big5-HKSCS | big5-hkscs | ||
| EUC-JP | cseucjpkdfmtjapanese, euc-jp, x-euc-jp | ||
| EUC-KR | 5601, csksc56011987, csueckr, euc-kr, iso-ir-149, korean, ks_c_5601-1989, ksc5601, ksc_5601 | x-windows-949 | |
| gb18030 | gb18030 | ||
| GB2312 | chinese, csgb2312, csiso58gb231280, gb2312, gb_2312, gb_2312-80, iso-ir-58, zh_cn.euc | x-gbk | |
| GEOSTD8 | geostd8 | Does not seem to work. | |
| HZ-GB-2312 | hz-gb-2312 | ||
| IBM850 | 850, cp850, csIBM850, ibm850 | csIBM850 not recognised. | |
| IBM852 | 852, cp852, csIBM852, ibm852 | csIBM852 not recognised. | |
| IBM855 | 855, cp855, csIBM855, ibm855 | csIBM855 not recognised. | |
| IBM857 | 857, cp857, csIBM857, ibm857 | csIBM857 not recognised. | |
| IBM862 | 862, cp862, csIBM862, ibm862 | csIBM862 not recognised. | |
| IBM864 | 864, cp864, csIBM864, ibm-864, ibm864 | csIBM864 not recognised. | |
| IBM864i | 864i, cp864i, csibm864i, ibm-864i, ibm864i | ||
| IBM866 | 866, cp-866, cp866, csIBM866, ibm866 | csIBM866 not recognised. | |
| ISO-2022-CN | iso-2022-cn, iso-2022-cn-ext | ||
| ISO-2022-JP | csiso2022jp, csiso2022jp2, iso-2022-jp, iso-2022-jp-2 | ||
| ISO-2022-KR | csiso2022kr, iso-2022-kr | ||
| ISO-8859-1 | cp819, csisolatin1, ibm819, iso-8859-1, iso-ir-100, iso8859-1, iso88591, iso_8859-1, l1, latin1 | windows-1252 | |
| ISO-8859-10 | csisolatin6, iso-8859-10, iso-ir-157, iso8859-10, iso885910, l6, latin6 | ||
| ISO-8859-11 | iso-8859-11, iso8859-11, iso885911 | windows-874 | |
| ISO-8859-13 | iso-8859-13, iso8859-13, iso885913 | ||
| ISO-8859-14 | iso-8859-14, iso8859-14, iso885914 | ||
| ISO-8859-15 | iso-8859-15, iso8859-15, iso885915, iso_8859-15 | ||
| ISO-8859-16 | iso-8859-16 | ||
| ISO-8859-2 | csisolatin2, iso-8859-2, iso-ir-101, iso8859-2, iso88592, iso_8859-2, l2, latin2 | ||
| ISO-8859-3 | csisolatin3, iso-8859-3, iso-ir-109, iso8859-3, iso88593, iso_8859-3, l3, latin3 | ||
| ISO-8859-4 | csisolatin4, iso-8859-4, iso-ir-110, iso8859-4, iso88594, iso_8859-4, l4, latin4 | ||
| ISO-8859-5 | csisolatincyrillic, cyrillic, iso-8859-5, iso-ir-144, iso8859-5, iso88595, iso_8859-5 | ||
| ISO-8859-6 | arabic, asmo-708, csisolatinarabic, ecma-114, iso-8859-6, iso-ir-127, iso8859-6, iso88596, iso_8859-6 | ||
| ISO-8859-6-E | csiso88596e, iso-8859-6-e | ||
| ISO-8859-6-I | csiso88596i, iso-8859-6-i | ||
| ISO-8859-7 | csisolatingreek, ecma-118, elot_928, greek, greek8, iso-8859-7, iso-ir-126, iso8859-7, iso88597, iso_8859-7, sun_eu_greek | ||
| ISO-8859-8 | csisolatinhebrew, hebrew, iso-8859-8, iso-ir-138, iso8859-8, iso88598, iso_8859-8, visual | ||
| ISO-8859-8-E | csiso88598e, iso-8859-8-e | ||
| ISO-8859-8-I | csiso88598i, iso-8859-8-i, iso-8859-8i | ||
| ISO-8859-9 | csisolatin5, iso-8859-9, iso-ir-148, iso8859-9, iso88599, iso_8859-9, l5, latin5 | ||
| ISO-IR-111 | csiso111ecmacyrillic, ecma-cyrillic, iso-ir-111 | ||
| KOI8-R | koi8-r | ||
| KOI8-U | koi8-u | ||
| Shift_JIS | csshiftjis, ms_kanji, shift-jis, shift_jis, windows-31j, x-sjis | ||
| T.61-8bit | csiso103t618bit, iso-ir-103, t.61, t.61-8bit | ||
| TIS-620 | tis-620, tis620 | windows-874 | |
| us-ascii | 646, ansi_x3.4-1968, ascii, us-ascii | windows-1252 | |
| UTF-16 | utf-16 | Recognized as BE or LE by BOM or byte sniffing | |
| UTF-16BE | csunicode, csunicode11, csunicodeascii, csunicodelatin1, iso-10646, iso-10646-j-1, iso-10646-ucs-2, iso-10646-ucs-basic, iso-10646-unicode-latin1, utf-16be, x-iso-10646-ucs-2-be | ||
| UTF-16LE | utf-16le, x-iso-10646-ucs-2-le | ||
| UTF-32 | utf-32 | Recognized as BE or LE by BOM or byte sniffing | |
| UTF-32BE | iso-10646-ucs-4, utf-32be, x-iso-10646-ucs-4-be | ||
| UTF-32LE | utf-32le, x-iso-10646-ucs-4-le | ||
| UTF-7 | csunicode11utf7, unicode-1-1-utf-7, unicode-2-0-utf-7, utf-7, x-unicode-2-0-utf-7 | ||
| UTF-8 | unicode-1-1-utf-8, utf-8, utf8 | ||
| VISCII | csviscii, viscii | ||
| windows-1250 | cp1250, windows-1250, x-cp1250 | ||
| windows-1251 | ansi-1251, cp1251, windows-1251, x-cp1251 | ||
| windows-1252 | cp1252, windows-1252, x-cp1252 | ||
| windows-1253 | cp1253, windows-1253, x-cp1253 | ||
| windows-1254 | cp1254, windows-1254, x-cp1254 | ||
| windows-1255 | cp1255, windows-1255, x-cp1255 | ||
| windows-1256 | cp1256, windows-1256, x-cp1256 | ||
| windows-1257 | cp1257, windows-1257, x-cp1257 | ||
| windows-1258 | cp1258, windows-1258, x-cp1258 | ||
| windows-874 | ibm874, windows-874 | ||
| windows-936 | windows-936 | ||
| x-euc-tw | cns11643, x-euc-tw, zh_tw-euc | ||
| x-gbk | gbk, x-gbk | ||
| x-imap4-modified-utf7 | x-imap4-modified-utf7 | ||
| x-johab | x-johab | ||
| x-mac-arabic | x-mac-arabic | ||
| x-mac-ce | x-mac-ce | ||
| x-mac-croatian | x-mac-croatian | ||
| x-mac-cyrillic | x-mac-cyrillic | ||
| x-mac-devanagari | x-mac-devanagari | ||
| x-mac-farsi | x-mac-farsi | ||
| x-mac-greek | x-mac-greek | ||
| x-mac-gujarati | x-mac-gujarati | ||
| x-mac-gurmukhi | x-mac-gurmukhi | ||
| x-mac-hebrew | x-mac-hebrew | ||
| x-mac-icelandic | x-mac-icelandic | ||
| x-mac-roman | csMacintosh, mac, macintosh, x-mac-roman | csMacintosh not recognised. | |
| x-mac-romanian | x-mac-romanian | ||
| x-mac-turkish | x-mac-turkish | ||
| x-mac-ukrainian | x-mac-ukrainian | ||
| x-user-defined | x-user-defined | ||
| x-viet-tcvn5712 | x-viet-tcvn5712 | ||
| x-viet-vps | x-viet-vps | ||
| x-windows-949 | ks_c_5601-1987, x-windows-949 |
Table generated from <http://mxr.mozilla.org/mozilla1.9.1/source/intl/uconv/src/charsetalias.properties> (corresponds to Firefox 3.5.2).
Aliases (used for parsing, apparently not for serialisation) are scattered around in a large number of files; cf. <http://mxr.mozilla.org/firefox/source/intl/uconv/ucvlatin/nsISO885911ToUnicode.cpp> for the mapping from ISO-8859-11 to windows-874.
8-bit encodings (excluding UTFs, CJK encodings and T.61) tested using <http://coq.no/X/charset5/tests8bit.html> (fail/pass should not be taken too seriously yet, especially not for more obscure encodings), Firefox version 3.5.1, OS X.
Bugs: Filed <https://bugzilla.mozilla.org/show_bug.cgi?id=512060> for the labels marked 'not recognised' in the table above since the lack of support for these is clearly accidental rather than deliberate (though it seems to suggest that these particular labels are not particularly widely used). In most other cases, research and deliberation will be needed to distinguish between bugs and features.
Chrome
Very much like Safari with some changes on top of ICU. Documented in the source...
Internet Explorer
Matching
Strips leading and trailing whitespace and then does ASCII(?) case-insensitive matching. (Matches HTML5.)
Encodings
Needs sorting out:
- http://blogs.msdn.com/shawnste/archive/2009/08/18/alternate-encoding-names-recognized-by-net-ie.aspx
- http://msdn.microsoft.com/en-us/library/system.text.encoding.getencodings.aspx
- http://web.archive.org/web/20080204211015/http://www.hitachi-to.co.jp/prod/prod_2/inter/emk/help/TextEncoder/CodePage.htm
Safari
Matching
UTS22
Encodings
Apple’s reference <http://developer.apple.com/documentation/Carbon/Conceptual/ProgWithTECM/tecmgr_encnames/tecmgr_encnames.html#//apple_ref/doc/uid/TP40000932-CH204-TPXREF103> is incomplete or at least severely out of date even as a description of the Text Encoding Conversion Manager (TECM).
Querying TECM programmatically gives labels for more encodings, but the set of encodings does not match what Safari currently supports.
According to webkit/WebCore/platform/text/TextCodecICU.cpp, WebKit now uses ICU <http://site.icu-project.org/> with additional aliases (webkit/WebCore/platform/text/TextCodecICU.cpp), additional encodings (webkit/WebCore/platform/text/mac/mac-encodings.txt) possibly implemented using TECM at least on the Mac, a list of official IANA labels (webkit/WebCore/platform/text/mac/character-sets.txt) and probably a few more which I have not noticed.
ICU 4.2’s icu/source/data/mappings/convrtrs.txt or <http://demo.icu-project.org/icu-bin/convexp> lists encodings and labels not supported in Safari 4.0 on Leopard, and webkit/WebCore/platform/text/TextCodecICU.cpp mentions that Tiger included ICU 3.2.
Does encoding support in Safari depend on OS and OS version, and will Safari ultimately support everything in ICU 4.2? -- Windows comes with ICU but does not support some of the encodings the Mac edition does.
Integrate notes from othermaciej in http://krijnhoetmer.nl/irc-logs/whatwg/20090909 Also: http://trac.webkit.org/browser/trunk/WebCore/platform/text