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<!doctype html>
<html lang=en-US>
<meta charset=utf-8>
<title>Encoding Standard</title>
<link rel=stylesheet href=//www.whatwg.org/style/specification>
<link rel=icon href=//resources.whatwg.org/logo-encoding.svg>
<div class=head>
<p><a class=logo href=//www.whatwg.org/><img alt=WHATWG src=//resources.whatwg.org/logo-encoding.svg width=100 height=100></a></p>
<h1>Encoding</h1>
<h2 class="no-num no-toc">Living Standard — Last Updated [DATE: 01 Jan 1901]</h2>
<dl>
<dt>This Version:
<dd><a href=http://encoding.spec.whatwg.org/>http://encoding.spec.whatwg.org/</a>
<dt>Participate:
(<a href="http://lists.w3.org/Archives/Public/www-international/">archives</a>) or
<a href="https://www.w3.org/Bugs/Public/enter_bug.cgi?product=WHATWG&component=Encoding">file a bug</a>
(<a href="https://www.w3.org/Bugs/Public/buglist.cgi?product=WHATWG&component=Encoding&resolution=---">open bugs</a>)
<dd><a href="http://wiki.whatwg.org/wiki/IRC">IRC: #whatwg on Freenode</a>
<dt>Version History:
<dd><a href=https://github.com/whatwg/encoding/commits>https://github.com/whatwg/encoding/commits</a>
<dd><a href=https://twitter.com/encodings>@encodings</a>
<dt>Editors:
<dd><a href="http://annevankesteren.nl/">Anne van Kesteren</a>
<dd>Joshua Bell (Google)
</dl>
<script src=//resources.whatwg.org/file-bug.js async></script>
<p class=copyright><a rel="license" href="http://creativecommons.org/publicdomain/zero/1.0/">CC0 1.0 Universal</a>.
To the extent possible under law, the editor has waived all copyright and
related or neighboring rights to this work. In addition, as of
[DATE: 01 Jan 1901], the editor has made this specification available
under the
<a rel="license"
href="http://www.openwebfoundation.org/legal/the-owf-1-0-agreements/owfa-1-0">Open Web Foundation Agreement Version 1.0</a>,
which is available at
http://www.openwebfoundation.org/legal/the-owf-1-0-agreements/owfa-1-0.
</div>
<h2 class="no-num no-toc">Table of Contents</h2>
<!--toc-->
<h2>Preface</h2>
<p>While encodings have been defined to some extent, implementations have
not always implemented them in the same way, have not always used the same
labels, and often differ in dealing with undefined and former proprietary
areas of encodings. This specification attempts to fill those gaps so that
new implementations do not have to reverse engineer encoding implementations
of the market leaders and existing implementations can converge.
<p class=note>This specification is primarily intended for dealing with
legacy content, it requires new content and formats to use the
<span>utf-8</span> <span>encoding</span> exclusively.
<h2>Conformance</h2>
<p>All diagrams, examples, and notes in this specification are
non-normative, as are all sections explicitly marked non-normative.
Everything else in this specification is normative.
<p>The key words "MUST", "MUST NOT", "REQUIRED", <!--"SHALL", "SHALL
NOT",--> "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and
"OPTIONAL" in the normative parts of this document are to be
interpreted as described in RFC2119. For readability, these words do
not appear in all uppercase letters in this specification.
<span data-anolis-ref>RFC2119</span>
<p>Conformance requirements phrased as algorithms or specific steps
may be implemented in any manner, so long as the end result is
equivalent. (In particular, the algorithms defined in this
specification are intended to be easy to follow, and not intended to
be performant.)
<p id="hardwareLimitations">User agents may impose
implementation-specific limits on otherwise unconstrained inputs,
e.g. to prevent denial of service attacks, to guard against running
out of memory, or to work around platform-specific limitations.
<h2>Terminology</h2>
<p>Hexadecimal numbers are prefixed with "0x".
<p>In equations, all numbers are integers, addition is represented by "+",
subtraction by "−", multiplication by "×", division by "/",
calculating the remainder of a division (also known as modulo) by "%",
exponentiation by "<var title>b</var><sup><var title>n</var></sup>",
arithmetic left shifts by "<<", arithmetic right shifts by ">>",
bitwise AND by "&", and bitwise OR by "|".
<p>A <dfn>byte</dfn> is a sequence of eight bits, represented as a
double-digit hexadecimal number in the range 0x00 to 0xFF.
<p>A <dfn>code point</dfn> is a Unicode code point and is represented as a
four-to-six digit hexadecimal number, typically prefixed with "U+".
In equations and <span title=index>indexes</span> code points are prefixed
with "0x". <span data-anolis-ref>UNICODE</span>
<p>The <dfn>ASCII whitespace</dfn> are code points U+0009, U+000A, U+000C,
U+000D, and U+0020.
<p>A <dfn>string</dfn> is a sequence of code points.
<p>Comparing two strings in an <dfn>ASCII case-insensitive</dfn> manner
means comparing them exactly, code point for code point, except that the
characters in the range U+0041 to U+005A (i.e. LATIN CAPITAL LETTER A to
LATIN CAPITAL LETTER Z) and the corresponding characters in the range
U+0061 to U+007A (i.e. LATIN SMALL LETTER A to LATIN SMALL LETTER Z) are
considered to also match.
<h2>Encodings</h2>
<p>An <dfn>encoding</dfn> defines a mapping from a code point sequence to a
byte sequence (and vice versa). Each <span>encoding</span> has a
<dfn>name</dfn>, and one or more <dfn title=label>labels</dfn>.
<p>Each <span>encoding</span> also has a <dfn>decoder</dfn> and
<dfn>encoder</dfn> algorithm.
<p>A <span>decoder</span> algorithm takes a byte stream and emits a
code point stream. The <dfn>byte pointer</dfn> is initially zero,
pointing to the first byte in the stream. It cannot be negative. It can be
increased and decreased to point to other bytes in the stream. The
<dfn>EOF byte</dfn> is a conceptual byte representing the end of the
stream. The <span>byte pointer</span> cannot point beyond the
<span>EOF byte</span>. The <dfn>EOF code point</dfn> is a conceptual code
point that is emitted once the byte stream is handled in its entirety.
A <dfn>decoder error</dfn> indicates an error in the byte stream.
Unless stated otherwise, emitting a <span>decoder error</span> must emit
code point U+FFFD.
A <span>decoder</span> must be invoked again when the word continue is used,
when one or more code points are emitted of which none is the
<span>EOF code point</span>, or when a <span>decoder error</span> is
emitted.
<p class=note>An XML processor would halt upon the first
<span>decoder error</span> emitted.
<p>An <span>encoder</span> algorithm takes a code point stream and emits a
byte stream. It fails when a code point is passed for which it does not have
a corresponding byte (sequence). Analogously to a <span>decoder</span>, it
has a <dfn>code point pointer</dfn> and <dfn>encoder error</dfn>.
An <span>encoder</span> must be invoked again when the word continue is
used, or when one or more bytes are emitted of which none is the
<span>EOF byte</span>. Unless stated otherwise, when an
<span>encoder error</span> is emitted the <span>encoder</span> terminates.
<p class=note>HTML forms and URLs require non-terminating
<span title=encoder>encoders</span> and have therefore special handling
whenever an <span>encoder error</span> is reached. Instead of terminating
the <span>encoder</span> one or more code points in the range
U+0000 to U+007F are inserted into the code point stream at
<span>code point pointer</span> after <span>encoder error</span> is emitted.
<hr>
<p>The table below lists all <span title=encoding>encodings</span>
and their <span title=label>labels</span> user agents must support.
User agents must not support any other <span title=encoding>encodings</span>
or <span title=label>labels</span>.
<p>Authors must use the <span>utf-8</span> <span>encoding</span> and must use the
"<code title>utf-8</code>" <span>label</span> to identify it.
<p>New protocols and formats must use the <span>utf-8</span> <span>encoding</span>
exclusively. If these protocols and formats need to expose the <span>encoding</span>'s
<span>label</span>, they must expose it as "<code title>utf-8</code>".
<p>To <dfn title=concept-encoding-get>get an encoding</dfn> from a string
<var title>label</var>, run these steps:
<ol>
<li><p>Remove any leading and trailing <span>ASCII whitespace</span> from
<var title>label</var>.
<li><p>If <var title>label</var> is an <span>ASCII case-insensitive</span>
match for any of the <span title=label>labels</span> listed in the table
below, return the corresponding <span>encoding</span>, and return failure
otherwise.
</ol>
<p class=note>In violation of
<a href="http://www.unicode.org/reports/tr22/tr22-7.html#Charset_Alias_Matching">section 1.4 of Unicode Technical Standard #22</a>
this is a much simpler and more restrictive matching algorithm, as that is
found to be necessary to be compatible with deployed content.
<table>
<thead>
<tr>
<th><span>Name</span>
<th><span title=label>Labels</span>
<tbody>
<tr><th colspan=2><a href=#the-encoding>The Encoding</a>
<tr>
<td rowspan=3><span>utf-8</span>
<td>"<code title>unicode-1-1-utf-8</code>"
<tr><td>"<code title>utf-8</code>"
<tr><td>"<code title>utf8</code>"
<tbody>
<tr><th colspan=2><a href=#legacy-single-byte-encodings>Legacy single-byte encodings</a>
<tr>
<td rowspan=4><span>ibm866</span>
<td>"<code title>866</code>"
<tr><td>"<code title>cp866</code>"
<tr><td>"<code title>csibm866</code>"
<tr><td>"<code title>ibm866</code>"
<tr>
<td rowspan=9><span>iso-8859-2</span>
<td>"<code title>csisolatin2</code>"
<tr><td>"<code title>iso-8859-2</code>"
<tr><td>"<code title>iso-ir-101</code>"
<tr><td>"<code title>iso8859-2</code>"
<tr><td>"<code title>iso88592</code>"
<tr><td>"<code title>iso_8859-2</code>"
<tr><td>"<code title>iso_8859-2:1987</code>"
<tr><td>"<code title>l2</code>"
<tr><td>"<code title>latin2</code>"
<tr>
<td rowspan=9><span>iso-8859-3</span>
<td>"<code title>csisolatin3</code>"
<tr><td>"<code title>iso-8859-3</code>"
<tr><td>"<code title>iso-ir-109</code>"
<tr><td>"<code title>iso8859-3</code>"
<tr><td>"<code title>iso88593</code>"
<tr><td>"<code title>iso_8859-3</code>"
<tr><td>"<code title>iso_8859-3:1988</code>"
<tr><td>"<code title>l3</code>"
<tr><td>"<code title>latin3</code>"
<tr>
<td rowspan=9><span>iso-8859-4</span>
<td>"<code title>csisolatin4</code>"
<tr><td>"<code title>iso-8859-4</code>"
<tr><td>"<code title>iso-ir-110</code>"
<tr><td>"<code title>iso8859-4</code>"
<tr><td>"<code title>iso88594</code>"
<tr><td>"<code title>iso_8859-4</code>"
<tr><td>"<code title>iso_8859-4:1988</code>"
<tr><td>"<code title>l4</code>"
<tr><td>"<code title>latin4</code>"
<tr>
<td rowspan=8><span>iso-8859-5</span>
<td>"<code title>csisolatincyrillic</code>"
<tr><td>"<code title>cyrillic</code>"
<tr><td>"<code title>iso-8859-5</code>"
<tr><td>"<code title>iso-ir-144</code>"
<tr><td>"<code title>iso8859-5</code>"
<tr><td>"<code title>iso88595</code>"
<tr><td>"<code title>iso_8859-5</code>"
<tr><td>"<code title>iso_8859-5:1988</code>"
<tr>
<td rowspan=14><span>iso-8859-6</span>
<td>"<code title>arabic</code>"
<tr><td>"<code title>asmo-708</code>"
<tr><td>"<code title>csiso88596e</code>"
<tr><td>"<code title>csiso88596i</code>"
<tr><td>"<code title>csisolatinarabic</code>"
<tr><td>"<code title>ecma-114</code>"
<tr><td>"<code title>iso-8859-6</code>"
<tr><td>"<code title>iso-8859-6-e</code>"
<tr><td>"<code title>iso-8859-6-i</code>"
<tr><td>"<code title>iso-ir-127</code>"
<tr><td>"<code title>iso8859-6</code>"
<tr><td>"<code title>iso88596</code>"
<tr><td>"<code title>iso_8859-6</code>"
<tr><td>"<code title>iso_8859-6:1987</code>"
<tr>
<td rowspan=12><span>iso-8859-7</span>
<td>"<code title>csisolatingreek</code>"
<tr><td>"<code title>ecma-118</code>"
<tr><td>"<code title>elot_928</code>"
<tr><td>"<code title>greek</code>"
<tr><td>"<code title>greek8</code>"
<tr><td>"<code title>iso-8859-7</code>"
<tr><td>"<code title>iso-ir-126</code>"
<tr><td>"<code title>iso8859-7</code>"
<tr><td>"<code title>iso88597</code>"
<tr><td>"<code title>iso_8859-7</code>"
<tr><td>"<code title>iso_8859-7:1987</code>"
<tr><td>"<code title>sun_eu_greek</code>"
<tr>
<td rowspan=11><span>iso-8859-8</span>
<td>"<code title>csiso88598e</code>"
<tr><td>"<code title>csisolatinhebrew</code>"
<tr><td>"<code title>hebrew</code>"
<tr><td>"<code title>iso-8859-8</code>"
<tr><td>"<code title>iso-8859-8-e</code>"
<tr><td>"<code title>iso-ir-138</code>"
<tr><td>"<code title>iso8859-8</code>"
<tr><td>"<code title>iso88598</code>"
<tr><td>"<code title>iso_8859-8</code>"
<tr><td>"<code title>iso_8859-8:1988</code>"
<tr><td>"<code title>visual</code>"
<tr>
<td rowspan=3><span>iso-8859-8-i</span>
<td>"<code title>csiso88598i</code>"
<tr><td>"<code title>iso-8859-8-i</code>"
<tr><td>"<code title>logical</code>"
<tr>
<td rowspan=7><span>iso-8859-10</span>
<td>"<code title>csisolatin6</code>"
<tr><td>"<code title>iso-8859-10</code>"
<tr><td>"<code title>iso-ir-157</code>"
<tr><td>"<code title>iso8859-10</code>"
<tr><td>"<code title>iso885910</code>"
<tr><td>"<code title>l6</code>"
<tr><td>"<code title>latin6</code>"
<tr>
<td rowspan=3><span>iso-8859-13</span>
<td>"<code title>iso-8859-13</code>"
<tr><td>"<code title>iso8859-13</code>"
<tr><td>"<code title>iso885913</code>"
<tr>
<td rowspan=3><span>iso-8859-14</span>
<td>"<code title>iso-8859-14</code>"
<tr><td>"<code title>iso8859-14</code>"
<tr><td>"<code title>iso885914</code>"
<tr>
<td rowspan=6><span>iso-8859-15</span>
<td>"<code title>csisolatin9</code>"
<tr><td>"<code title>iso-8859-15</code>"
<tr><td>"<code title>iso8859-15</code>"
<tr><td>"<code title>iso885915</code>"
<tr><td>"<code title>iso_8859-15</code>"
<tr><td>"<code title>l9</code>"
<tr>
<td><span>iso-8859-16</span>
<td>"<code title>iso-8859-16</code>"
<tr>
<td rowspan=5><span>koi8-r</span>
<td>"<code title>cskoi8r</code>"
<tr><td>"<code title>koi</code>"
<tr><td>"<code title>koi8</code>"
<tr><td>"<code title>koi8-r</code>"
<tr><td>"<code title>koi8_r</code>"
<tr>
<td><span>koi8-u</span>
<td>"<code title>koi8-u</code>"
<tr>
<td rowspan=4><span>macintosh</span>
<td>"<code title>csmacintosh</code>"
<tr><td>"<code title>mac</code>"
<tr><td>"<code title>macintosh</code>"
<tr><td>"<code title>x-mac-roman</code>"
<tr>
<td rowspan=6><span>windows-874</span>
<td>"<code title>dos-874</code>"
<tr><td>"<code title>iso-8859-11</code>"
<tr><td>"<code title>iso8859-11</code>"
<tr><td>"<code title>iso885911</code>"
<tr><td>"<code title>tis-620</code>"
<tr><td>"<code title>windows-874</code>"
<tr>
<td rowspan=3><span>windows-1250</span>
<td>"<code title>cp1250</code>"
<tr><td>"<code title>windows-1250</code>"
<tr><td>"<code title>x-cp1250</code>"
<tr>
<td rowspan=3><span>windows-1251</span>
<td>"<code title>cp1251</code>"
<tr><td>"<code title>windows-1251</code>"
<tr><td>"<code title>x-cp1251</code>"
<tr>
<td rowspan=17><span>windows-1252</span>
<td>"<code title>ansi_x3.4-1968</code>"
<tr><td>"<code title>ascii</code>"
<tr><td>"<code title>cp1252</code>"
<tr><td>"<code title>cp819</code>"
<tr><td>"<code title>csisolatin1</code>"
<tr><td>"<code title>ibm819</code>"
<tr><td>"<code title>iso-8859-1</code>"
<tr><td>"<code title>iso-ir-100</code>"
<tr><td>"<code title>iso8859-1</code>"
<tr><td>"<code title>iso88591</code>"
<tr><td>"<code title>iso_8859-1</code>"
<tr><td>"<code title>iso_8859-1:1987</code>"
<tr><td>"<code title>l1</code>"
<tr><td>"<code title>latin1</code>"
<tr><td>"<code title>us-ascii</code>"
<tr><td>"<code title>windows-1252</code>"
<tr><td>"<code title>x-cp1252</code>"
<tr>
<td rowspan=3><span>windows-1253</span>
<td>"<code title>cp1253</code>"
<tr><td>"<code title>windows-1253</code>"
<tr><td>"<code title>x-cp1253</code>"
<tr>
<td rowspan=12><span>windows-1254</span>
<td>"<code title>cp1254</code>"
<tr><td>"<code title>csisolatin5</code>"
<tr><td>"<code title>iso-8859-9</code>"
<tr><td>"<code title>iso-ir-148</code>"
<tr><td>"<code title>iso8859-9</code>"
<tr><td>"<code title>iso88599</code>"
<tr><td>"<code title>iso_8859-9</code>"
<tr><td>"<code title>iso_8859-9:1989</code>"
<tr><td>"<code title>l5</code>"
<tr><td>"<code title>latin5</code>"
<tr><td>"<code title>windows-1254</code>"
<tr><td>"<code title>x-cp1254</code>"
<tr>
<td rowspan=3><span>windows-1255</span>
<td>"<code title>cp1255</code>"
<tr><td>"<code title>windows-1255</code>"
<tr><td>"<code title>x-cp1255</code>"
<tr>
<td rowspan=3><span>windows-1256</span>
<td>"<code title>cp1256</code>"
<tr><td>"<code title>windows-1256</code>"
<tr><td>"<code title>x-cp1256</code>"
<tr>
<td rowspan=3><span>windows-1257</span>
<td>"<code title>cp1257</code>"
<tr><td>"<code title>windows-1257</code>"
<tr><td>"<code title>x-cp1257</code>"
<tr>
<td rowspan=3><span>windows-1258</span>
<td>"<code title>cp1258</code>"
<tr><td>"<code title>windows-1258</code>"
<tr><td>"<code title>x-cp1258</code>"
<tr>
<td rowspan=2><span>x-mac-cyrillic</span>
<td>"<code title>x-mac-cyrillic</code>"
<tr><td>"<code title>x-mac-ukrainian</code>"
<tbody>
<tr><th colspan=2><a href=#legacy-multi-byte-chinese-(simplified)-encodings>Legacy multi-byte Chinese (simplified) encodings</a>
<tr>
<td rowspan=9><span>gbk</span>
<td>"<code title>chinese</code>"
<tr><td>"<code title>csgb2312</code>"
<tr><td>"<code title>csiso58gb231280</code>"
<tr><td>"<code title>gb2312</code>"
<tr><td>"<code title>gb_2312</code>"
<tr><td>"<code title>gb_2312-80</code>"
<tr><td>"<code title>gbk</code>"
<tr><td>"<code title>iso-ir-58</code>"
<tr><td>"<code title>x-gbk</code>"
<tr>
<td><span>gb18030</span>
<td>"<code title>gb18030</code>"
<tr>
<td><span>hz-gb-2312</span>
<td>"<code title>hz-gb-2312</code>"
<tbody>
<tr><th colspan=2><a href=#legacy-multi-byte-chinese-(traditional)-encodings>Legacy multi-byte Chinese (traditional) encodings</a>
<tr>
<td rowspan=5><span>big5</span>
<td>"<code title>big5</code>"
<tr><td>"<code title>big5-hkscs</code>"
<tr><td>"<code title>cn-big5</code>"
<tr><td>"<code title>csbig5</code>"
<tr><td>"<code title>x-x-big5</code>"
<tbody>
<tr><th colspan=2><a href=#legacy-multi-byte-japanese-encodings>Legacy multi-byte Japanese encodings</a>
<tr>
<td rowspan=3><span>euc-jp</span>
<td>"<code title>cseucpkdfmtjapanese</code>"
<tr><td>"<code title>euc-jp</code>"
<tr><td>"<code title>x-euc-jp</code>"
<tr>
<td rowspan=2><span>iso-2022-jp</span>
<td>"<code title>csiso2022jp</code>"
<tr><td>"<code title>iso-2022-jp</code>"
<tr>
<td rowspan=7><span>shift_jis</span>
<td>"<code title>csshiftjis</code>"
<tr><td>"<code title>ms_kanji</code>"
<tr><td>"<code title>shift-jis</code>"
<tr><td>"<code title>shift_jis</code>"
<tr><td>"<code title>sjis</code>"
<tr><td>"<code title>windows-31j</code>"
<tr><td>"<code title>x-sjis</code>"
<tbody>
<tr><th colspan=2><a href=#legacy-multi-byte-korean-encodings>Legacy multi-byte Korean encodings</a>
<tr>
<td rowspan=10><span>euc-kr</span>
<td>"<code title>cseuckr</code>"
<tr><td>"<code title>csksc56011987</code>"
<tr><td>"<code title>euc-kr</code>"
<tr><td>"<code title>iso-ir-149</code>"
<tr><td>"<code title>korean</code>"
<tr><td>"<code title>ks_c_5601-1987</code>"
<tr><td>"<code title>ks_c_5601-1989</code>"
<tr><td>"<code title>ksc5601</code>"
<tr><td>"<code title>ksc_5601</code>"
<tr><td>"<code title>windows-949</code>"
<tr>
<td rowspan=2><span>iso-2022-kr</span>
<td>"<code title>csiso2022kr</code>"
<tr><td>"<code title>iso-2022-kr</code>"
<tbody>
<tr><th colspan=2><a href=#legacy-miscellaneous-encodings>Legacy miscellaneous encodings</a>
<tr>
<td rowspan=2><span>replacement</span>
<td>"<code title>iso-2022-cn</code>"
<tr><td>"<code title>iso-2022-cn-ext</code>"
<tr>
<td><span>utf-16be</span>
<td>"<code title>utf-16be</code>"
<tr>
<td rowspan=2><span>utf-16le</span>
<td>"<code title>utf-16</code>"
<tr><td>"<code title>utf-16le</code>"
<tr>
<td><span>x-user-defined</span>
<td>"<code title>x-user-defined</code>"
</table>
<p class=note>All <span title=encoding>encodings</span> and their
<span title=label>labels</span> are also available as non-normative
<a href=encodings.json>encodings.json</a> resource.
<h2>Indexes</h2>
<p>Most legacy <span title=encoding>encodings</span> make use of
an <dfn>index</dfn>. An <span>index</span> is an ordered list of
pointers and corresponding code points. Within an <span>index</span>
pointers are unique and code points can be duplicated.
<p>To find the pointers and their corresponding code points in an <span>index</span>,
let <var title>lines</var> be the result of splitting the resource's contents on U+000A.
Then remove each item in <var title>lines</var> that is the empty string or starts with U+0023.
Then the pointers and their corresponding code points are found by splitting each item in <var title>lines</var> on U+0009.
The first subitem is the pointer (as a decimal number) and the second is the corresponding code point (as a hexadecimal number).
Other subitems are not relevant.
<p>The <dfn>index code point</dfn> for <var title>pointer</var> in
<var title>index</var> is the code point corresponding to
<var title>pointer</var> in <var title>index</var>, or null if
<var title>pointer</var> is not in <var title>index</var>.
<p>The <dfn>index pointer</dfn> for <var title>code point</var> in
<var title>index</var> is the <em>first</em> pointer corresponding to
<var title>code point</var> in <var title>index</var>, or null if
<var title>code point</var> is not in <var title>index</var>.
<p>These are the <span title=index>indexes</span> defined by this
specification, excluding <span>index single-byte</span>:
<table>
<tr><th colspan=2><span>Index</span><th>Notes
<tr>
<td><dfn>index big5</dfn>
<td><a href=index-big5.txt>index-big5.txt</a>
<td>This matches the Big5 standard in combination with the
Hong Kong Supplementary Character Set and other common extensions.
<tr>
<td><dfn>index euc-kr</dfn>
<td><a href=index-euc-kr.txt>index-euc-kr.txt</a>
<td>This matches the KS X 1001 standard and the Unified Hangul Code, more
commonly known together as Windows Codepage 949.
<tr>
<td><dfn>index gbk</dfn>
<td><a href=index-gbk.txt>index-gbk.txt</a>
<td>This matches the GB18030 standard for code points encoded as two
bytes.
<tr>
<td><dfn>index gb18030</dfn>
<td><a href=index-gb18030.txt>index-gb18030.txt</a>
<td>This <span>index</span> works different from all others. Listing all
code points would result in over a million items whereas they can be
represented neatly in 207 ranges combined with trivial limit checks. It
therefore only superficially matches the GB18030 standard for code points
encoded as four bytes. See also <span>index gb18030 code point</span> and
<span>index gb18030 pointer</span> below.
<tr>
<td><dfn>index jis0208</dfn>
<td><a href=index-jis0208.txt>index-jis0208.txt</a>
<td>This is the JIS X 0208 standard including formerly proprietary
extensions from IBM and NEC.
<!-- NEC = Nippon Electronics Corporation -->
<tr>
<td><dfn>index jis0212</dfn>
<td><a href=index-jis0212.txt>index-jis0212.txt</a>
<td>This is the JIS X 0212 standard.
</table>
<p>The <dfn>index gb18030 code point</dfn> for <var title>pointer</var> is
the return value of these steps:
<ol>
<li><p>If <var title>pointer</var> is greater than 39419 and less than
189000, or <var title>pointer</var> is greater than 1237575, return null.
<li><p>Let <var title>offset</var> be the last pointer in
<span>index gb18030</span> that is equal to or less than
<var title>pointer</var> and let <var title>code point offset</var> be its
corresponding code point.
<li><p>Return a code point whose value is
<var title>code point offset</var> + <var title>pointer</var> − <var title>offset</var>.
</ol>
<p>The <dfn>index gb18030 pointer</dfn> for <var title>code point</var> is
the return value of these steps:
<ol>
<li><p>Let <var title>offset</var> be the last code point in
<span>index gb18030</span> that is equal to or less than
<var title>code point</var> and let <var title>pointer offset</var> be its
corresponding pointer.
<li><p>Return a pointer whose value is
<var title>pointer offset</var> + <var title>code point</var> − <var title>offset</var>.
</ol>
<p class=note>All <span title=index>indexes</span> are also available as
non-normative <a href=indexes.json>indexes.json</a> resource.
(<span>index gb18030</span> has a slightly different format here, to be able
to represent ranges.)
<h2>Decode and encode</h2>
<p class=note>The algorithms <span>decode</span>, <span>utf-8 decode</span>,
and <span>encode</span> are intended for usage by other specifications.
<span>utf-8 decode</span> is to be used by new formats. The
<span title=concept-encoding-get>get an encoding</span> algorithm can be
used first to turn a <span>label</span> into an <span>encoding</span>.
<p>To <dfn>decode</dfn> a byte stream <var title>stream</var> using
fallback encoding <var title>encoding</var>, run these steps:
<ol>
<li><p>Let <var title>offset</var> be 0.
<li>
<p>For each of the rows in the following table, starting with the first
one and going down, if the first bytes of <var title>stream</var> match
all the bytes given in the first column (ergo <var title>stream</var>
contains at least two or three bytes), then set <var title>encoding</var>
to the <span>encoding</span> given in the cell in the second column of
that row, and set <var title>offset</var> to the offset given in the cell
in the third column of that row.
<table>
<tr><th>Byte order mark<th>Encoding<th>Offset
<tr><td>0xFF 0xFE<td><span>utf-16le</span><td>2
<tr><td>0xFE 0xFF<td><span>utf-16be</span><td>2
<tr><td>0xEF 0xBB 0xBF<td><span>utf-8</span><td>3
</table>
<p class=note>For compatibility with deployed content, the byte order mark
(also known as BOM) is considered more authoritative than anything else.
<li><p>Return the result of running <var title>encoding</var>'s
<span>decoder</span> with <span>byte pointer</span> set to
<var title>offset</var>, on <var title>stream</var>.
</ol>
<p>To <dfn>utf-8 decode</dfn> a byte stream <var title>stream</var>, run
these steps:
<ol>
<li><p>Let <var title>offset</var> be 0.
<li><p>If <var title>stream</var> contains at least three bytes and its
first three bytes match 0xEF 0xBB 0xBF, set <var title>offset</var> to 3.
<li><p>Return the result of running the <span>utf-8 decoder</span> with
<span>byte pointer</span> set to <var title>offset</var>, on
<var title>stream</var>.
</ol>
<hr>
<p>To <dfn>encode</dfn> a code point stream <var title>stream</var> using
encoding <var title>encoding</var>, return the result of running
<var title>encoding</var>'s <span>encoder</span> on <var title>stream</var>.
<p>To <dfn>utf-8 encode</dfn> a code point stream <var title>stream</var>,
return the result of <span title=encode>encoding</span>
<var title>stream</var> using encoding <span>utf-8</span>.
<p class=note>If the input to this algorithm stems from a DOMString, the
<span data-anolis-spec=webidl>convert a DOMString to a sequence of Unicode characters</span>
from Web IDL is to be used first.
<h2>API</h2>
<!-- http://wiki.whatwg.org/wiki/StringEncoding -->
<p>This section uses terminology from the DOM, Typed Arrays, and Web IDL.
Non-browser implementations are not required to implement this API.
<span data-anolis-ref>DOM</span>
<span data-anolis-ref>TYPEDARRAY</span>
<span data-anolis-ref>WEBIDL</span>
<div class=example>
<p>The following example uses the <code>TextEncoder</code> object to encode
an array of strings into an
<code data-anolis-spec=typedarray>ArrayBuffer</code>. The result is a
<code data-anolis-spec=typedarray>Uint8Array</code> containing the number
of strings (as a <code data-anolis-spec=typedarray>Uint32Array</code>),
followed by the length of the first string (as a
<code data-anolis-spec=typedarray>Uint32Array</code>), the
<span>utf-8</span> encoded string data, the length of the second string (as
a <code data-anolis-spec=typedarray>Uint32Array</code>), the string data,
and so on.
<pre><code>function encodeArrayOfStrings(strings, encoding) {
var encoder, encoded, len, i, bytes, view, offset;
encoder = TextEncoder(encoding);
encoded = [];
len = Uint32Array.BYTES_PER_ELEMENT;
for (i = 0; i < strings.length; i += 1) {
len += Uint32Array.BYTES_PER_ELEMENT;
encoded[i] = TextEncoder(encoding).encode(strings[i]);
len += encoded[i].byteLength;
}
bytes = new Uint8Array(len);
view = new DataView(bytes.buffer);
offset = 0;
view.setUint32(offset, strings.length);
offset += Uint32Array.BYTES_PER_ELEMENT;
for (i = 0; i < encoded.length; i += 1) {
len = encoded[i].byteLength;
view.setUint32(offset, len);
offset += Uint32Array.BYTES_PER_ELEMENT;
bytes.set(encoded[i], offset);
offset += len;
}
return bytes.buffer;
}</code></pre>
<p>The following example decodes an
<code data-anolis-spec=typedarray>ArrayBuffer</code> containing data
encoded in the format produced by the previous example back into an array
of strings.
<pre><code>function decodeArrayOfStrings(buffer, encoding) {
var decoder, view, offset, num_strings, strings, i, len;
decoder = TextDecoder(encoding);
view = new DataView(buffer);
offset = 0;
strings = [];
num_strings = view.getUint32(offset);
offset += Uint32Array.BYTES_PER_ELEMENT;
for (i = 0; i < num_strings; i += 1) {
len = view.getUint32(offset);
offset += Uint32Array.BYTES_PER_ELEMENT;
strings[i] = decoder.decode(
new DataView(view.buffer, offset, len));
offset += len;
}
return strings;
}</code></pre>
</div>
<h3>Interface <code title>TextDecoder</code></h3>
<pre class=idl>dictionary <dfn>TextDecoderOptions</dfn> {
boolean fatal = false;
};
dictionary <dfn>TextDecodeOptions</dfn> {
boolean stream = false;
};
[<span title=dom-TextDecoder>Constructor</span>(optional DOMString <var title>label</var> = "utf-8", optional <span>TextDecoderOptions</span> <var title>options</var>)]
interface <dfn>TextDecoder</dfn> {
readonly attribute DOMString <span title=dom-TextDecoder-encoding>encoding</span>;
DOMString <span title=dom-TextDecoder-decode>decode</span>();
DOMString <span title=dom-TextDecoder-decode>decode</span>(<span data-anolis-spec=typedarray>ArrayBufferView</span> <var title>input</var>, optional <span>TextDecodeOptions</span> <var title>options</var>);
};</pre>
<p>A <code>TextDecoder</code> object has an associated
<b>encoding</b>, <b>encoding state</b>, <b>stream</b>,
<b>BOM seen flag</b> (initially unset), <b>fatal flag</b> (initially unset)
and <b>streaming flag</b> (initially unset).
<dl class=domintro>
<dt><code><var title>decoder</var> = new <span title=dom-TextDecoder>TextDecoder</span>([<var title>label</var> = "utf-8" [, <var title>options</var>]])</code>
<dd>
<p>Returns a new <code>TextDecoder</code> object.
<p>If <var title>label</var> is either not a <span>label</span> or is a
<span>label</span> for <span>replacement</span>,
<span data-anolis-spec=webidl title=throw>throws</span> a
<code>TypeError</code>.
<dt><code><var title>decoder</var> . <span title=dom-TextDecoder-encoding>encoding</span></code>
<dd><p>Returns <b>encoding</b>'s <span>name</span>.
<dt><code><var title>decoder</var> . <span title=dom-TextDecoder-decode>decode</span>([<var title>input</var> [, <var title>options</var>]])</code>
<dd>
<p>Returns the result of running <b>encoding</b>'s
<span>decoder</span>. If <var title>options</var>'s
<code title>stream</code> is set to true the method can be invoked
multiple times to process a fragmented stream.
<p>If the <b>fatal flag</b> is set and <b>encoding</b>'s
<span>decoder</span> emits a <span>decoder error</span>,
<span data-anolis-spec=dom title=concept-throw>throws</span> an
"<code data-anolis-spec=dom>EncodingError</code>".
</dl>
<p>The
<dfn title=dom-TextDecoder><code>TextDecoder(<var title>label</var>, <var title>options</var>)</code></dfn>
constructor must run these steps:
<ol>
<li><p>Let <var title>encoding</var> be the result of
<span title=concept-encoding-get>getting an encoding</span> from
<var title>label</var>.
<li><p>If <var title>encoding</var> is failure or <span>replacement</span>,
<span data-anolis-spec=webidl>throw</span> a <code>TypeError</code>.
<li><p>Let <var title>dec</var> be a new <code>TextDecoder</code> object.
<li><p>Set <var title>dec</var>'s <b>encoding</b> to
<var title>encoding</var>.
<li><p>Set <var title>dec</var>'s <b>encoding state</b> to the default
values of <var title>dec</var>'s <b>encoding</b>'s <span>decoder</span>'s
associated variables.
<li><p>If <var title>options</var>'s <code title>fatal</code> member is
true, set <var title>dec</var>'s <b>fatal flag</b>.
<li><p>Return <var title>dec</var>.
</ol>
<p>The <dfn title=dom-TextDecoder-encoding><code>encoding</code></dfn>
attribute must return <b>encoding</b>'s <span>name</span>.
<p>The
<dfn title=dom-TextDecoder-decode><code>decode(<var title>input</var>, <var title>options</var>)</code></dfn>
method must run these steps:
<ol>
<li><p>If the <b>streaming flag</b> is unset, set the <b>encoding state</b>
to the default values of the <b>encoding</b>'s <span>decoder</span>'s
associated variables and empty the <b>stream</b>.
<li><p>If <var title>options</var>'s <code title>stream</code> is true,
set the <b>streaming flag</b>, and unset the <b>streaming flag</b>
otherwise.
<li><p>If <var title>input</var> is given, then given
<var title>input</var>'s <code title>buffer</code>,
<code title>byteOffset</code>, and <code title>byteLength</code>, append
<code title>byteLength</code> bytes from <code title>buffer</code>,
starting at <code title>byteOffset</code>, to the <b>stream</b>.
<!-- TYPEDARRAY really needs to make this simpler -->
<li>
<p>If the <b>BOM seen flag</b> is unset, and the <b>stream</b> either
holds at least two bytes, or at least three bytes if the <b>encoding</b>
is <span>utf-8</span>, then set the <b>BOM seen flag</b>, and for each of
the rows in the following table, starting with the first one and going
down, if the first bytes of the <b>stream</b> match all the bytes given in
the first column, and the <b>encoding</b> matches the
<span>encoding</span> given in the cell in the second column of that row,
then remove those bytes at the start of the <b>stream</b>.
<table>
<tr><th>Byte order mark<th>Encoding
<tr><td>0xFF 0xFE<td><span>utf-16le</span>
<tr><td>0xFE 0xFF<td><span>utf-16be</span>
<tr><td>0xEF 0xBB 0xBF<td><span>utf-8</span>
</table>
<p class=note>This algorithm is intentionally different from the
<span>decode</span> algorithm used by the rest of the platform to give API
users more control.
<li><p>If the <b>streaming flag</b> is unset, append the
<span>EOF byte</span> to the <b>stream</b>.
<li>
<p>Return the output of running <b>encoding</b>'s <span>decoder</span> on
the <b>stream</b>. If the <b>fatal flag</b> is set and
<b>encoding</b>'s <span>decoder</span> emits a <span>decoder error</span>,
<span data-anolis-spec=dom title=concept-throw>throw</span> a
"<code title>EncodingError</code>".
<p class=note>In addition to the reason given above with respect to the
byte order mark, this also does not use the <span>encode</span> algorithm
as it assumes a continuous stream rather than one delivered in fragments.
</ol>
<h3>Interface <code title>TextEncoder</code></h3>
<pre class=idl>dictionary <dfn>TextEncodeOptions</dfn> {
boolean stream = false;
};
[<span title=dom-TextEncoder>Constructor</span>(optional DOMString <var title>utfLabel</var> = "utf-8")]
interface <dfn>TextEncoder</dfn> {
readonly attribute DOMString <span title=dom-TextEncoder-encoding>encoding</span>;
<span data-anolis-spec=typedarray>Uint8Array</span> <span title=dom-TextEncoder-encode>encode</span>(optional DOMString <var title>input</var> = "", optional <span>TextEncodeOptions</span> <var title>options</var>);
};</pre>
<p>A <code>TextEncoder</code> object has an associated
<b>encoding</b>, <b>encoding state</b>, <b>stream</b>, and
<b>streaming flag</b> (initially unset).
<dl class=domintro>
<dt><code><var title>encoder</var> = new <span title=dom-TextEncoder>TextEncoder</span>([<var title>utfLabel</var> = "utf-8"])</code>
<dd>
<p>Returns a new <code>TextEncoder</code> object.
<p>If <var title>utfLabel</var> is not a <span>label</span> for
<span>utf-8</span>, <span>utf-16le</span>, or <span>utf-16be</span>,
<span data-anolis-spec=webidl title=throw>throws</span> a
<code>TypeError</code>.
<dt><code><var title>encoder</var> . <span title=dom-TextEncoder-encoding>encoding</span></code>
<dd><p>Returns <b>encoding</b>'s <span>name</span>.
<dt><code><var title>encoder</var> . <span title=dom-TextEncoder-encode>encode</span>([<var title>input</var> [, <var title>options</var>]])</code>
<dd><p>Returns the result of running <b>encoding</b>'s
<span>encoder</span>. If <var title>options</var>'s
<code title>stream</code> is set to true, the method can be invoked
multiple times to process a fragmented stream.
</dl>
<p>The
<dfn title=dom-TextEncoder><code>TextEncoder(<var title>utfLabel</var>)</code></dfn>
constructor must run these steps:
<ol>
<li><p>Let <var title>encoding</var> be the result of
<span title=concept-encoding-get>getting an encoding</span> from
<var title>utfLabel</var>.
<li><p>If <var title>encoding</var> is failure, or is none of
<span>utf-8</span>, <span>utf-16le</span>, and <span>utf-16be</span>,
<span data-anolis-spec=webidl>throw</span> a <code>TypeError</code>.
<li><p>Let <var title>enc</var> be a new <code>TextEncoder</code> object.
<li><p>Set <var title>enc</var>'s <b>encoding</b> to
<var title>encoding</var>.
<li><p>Set <var title>enc</var>'s <b>encoding state</b> to the default
values of <var title>enc</var>'s <b>encoding</b>'s <span>encoder</span>'s
associated variables.
<li><p>Return <var title>enc</var>.
</ol>
<p>The <dfn title=dom-TextEncoder-encoding><code>encoding</code></dfn>
attribute must return <b>encoding</b>'s <span>name</span>.
<p>The
<dfn title=dom-TextEncoder-encode><code>encode(<var title>input</var>, <var title>options</var>)</code></dfn>
method must run these steps:
<ol>
<li><p>If the <b>streaming flag</b> is unset, then set the
<b>encoding state</b> to the default values of the <b>encoding</b>'s
<span>encoder</span>'s associated variables, and empty the <b>stream</b>.
<li><p>If <var title>options</var>'s <code title>stream</code> is true,
set the <b>streaming flag</b>, and unset the <b>streaming flag</b>
otherwise.
<li><p>Append the result of
<span data-anolis-spec=webidl title="convert a DOMString to a sequence of Unicode characters">converting <var title>input</var> to Unicode</span>
to the <b>stream</b>.
<li><p>If the <b>streaming flag</b> is unset, append the
<span>EOF code point</span> to the <b>stream</b>.
<li>
<p>Let <var title>bytes</var> be the output of running