GeezerVison

1. Preface

The UTF-8 encoding is the most appropriate encoding for interchange of Unicode, the universal coded character set. Therefore, for new protocols and formats, as well as existing formats deployed in new contexts, this specification requires (and defines) the UTF-8 encoding.

The other (legacy) encodings have been defined to some extent in the past. However, user agents 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 addresses those gaps so that new user agents do not have to reverse engineer encoding implementations and existing user agents can converge.

In particular, this specification defines all those encodings, their algorithms to go from bytes to scalar values and back, and their canonical names and identifying labels. This specification also defines an API to expose part of the encoding algorithms to JavaScript.

User agents have also significantly deviated from the labels listed in the IANA Character Sets registry. To stop spreading legacy encodings further, this specification is exhaustive about the aforementioned details and therefore has no need for the registry. In particular, this specification does not provide a mechanism for extending any aspect of encodings.

2. Security background

There is a set of encoding security issues when the producer and consumer do not agree on the encoding in use, or on the way a given encoding is to be implemented. For instance, an attack was reported in 2011 where a Shift_JIS leading byte 0x82 was used to “mask” a 0x22 trailing byte in a JSON resource of which an attacker could control some field. The producer did not see the problem even though this is an illegal byte combination. The consumer decoded it as a single U+FFFD (�) and therefore changed the overall interpretation as U+0022 (") is an important delimiter. Decoders of encodings that use multiple bytes for scalar values now require that in case of an illegal byte combination, a scalar value in the range U+0000 to U+007F, inclusive, cannot be “masked”. For the aforementioned sequence the output would be U+FFFD U+0022. (As an unfortunate exception to this, the gb18030 decoder will “mask” up to one such byte at end-of-queue.)

This is a larger issue for encodings that map anything that is an ASCII byte to something that is not an ASCII code point, when there is no leading byte present. These are “ASCII-incompatible” encodings and other than ISO-2022-JP and UTF-16BE/LE, which are unfortunately required due to deployed content, they are not supported. (Investigation is ongoing whether more labels of other such encodings can be mapped to the replacement encoding, rather than the unknown encoding fallback.) An example attack is injecting carefully crafted content into a resource and then encouraging the user to override the encoding, resulting in, e.g., script execution.

Encoders used by URLs found in HTML and HTML’s form feature can also result in slight information loss when an encoding is used that cannot represent all scalar values. E.g., when a resource uses the windows-1252 encoding a server will not be able to distinguish between an end user entering “💩” and “💩” into a form.

The problems outlined here go away when exclusively using UTF-8, which is one of the many reasons that is now the mandatory encoding for all things.

See also the Browser UI chapter.

3. Terminology

This specification depends on the Infra Standard. [INFRA]

Hexadecimal numbers are prefixed with "0x".

In equations, all numbers are integers, addition is represented by "+", subtraction by "−", multiplication by "×", integer division by "/" (returns the quotient), modulo by "%" (returns the remainder of an integer division), logical left shifts by "<<", logical right shifts by ">>", bitwise AND by "&", and bitwise OR by "|".

For logical right shifts operands must have at least twenty-one bits precision.

An I/O queue is a type of list with items of a particular type (i.e., bytes or scalar values). End-of-queue is a special item that can be present in I/O queues of any type and it signifies that there are no more items in the queue.

Inserting the bytes « 0xF0, 0x9F » in an I/O queue « 0x92 0xA9, end-of-queue », results in an I/O queue « 0xF0, 0x9F, 0x92 0xA9, end-of-queue ». The next item to be read would be 0xF0.

The Infra standard is expected to define some infrastructure around type conversions. See whatwg/infra issue #319. [INFRA]

I/O queues are defined as lists, not queues, because they feature a restore operation. However, this restore operation is an internal detail of the algorithms in this specification, and is not to be used by other standards. Implementations are free to find alternative ways to implement such algorithms, as detailed in Implementation considerations.

4. Encodings

An encoding defines a mapping from a scalar value sequence to a byte sequence (and vice versa). Each encoding has a name, and one or more labels.

This specification defines three encodings with the same names as encoding schemes defined in the Unicode standard: UTF-8, UTF-16LE, and UTF-16BE. The encodings differ from the encoding schemes by byte order mark (also known as BOM) handling not being part of the encodings themselves and instead being part of wrapper algorithms in this specification, whereas byte order mark handling is part of the definition of the encoding schemes in the Unicode Standard. UTF-8 used together with the UTF-8 decode algorithm matches the encoding scheme of the same name. This specification does not provide wrapper algorithms that would combine with UTF-16LE and UTF-16BE to match the similarly-named encoding schemes. [UNICODE]

4.1. Encoders and decoders

Each encoding has an associated decoder and most of them have an associated encoder. Instances of decoders and encoders have a handler algorithm and might also have state. A handler algorithm takes an input I/O queue and an item, and returns finished, one or more items, error optionally with a code point, or continue.

The replacement and UTF-16BE/LE encodings have no encoder.

An error mode as used below is "replacement" or "fatal" for a decoder and "fatal" or "html" for an encoder.

An XML processor would set error mode to "fatal". [XML]

"html" exists as error mode due to HTML forms requiring a non-terminating legacy encoder. The "html" error mode causes a sequence to be emitted that cannot be distinguished from legitimate input and can therefore lead to silent data loss. Developers are strongly encouraged to use the UTF-8 encoding to prevent this from happening. [HTML]

4.2. Names and labels

The table below lists all encodings and their labels user agents must support. User agents must not support any other encodings or labels.

For each encoding, ASCII-lowercasing its name yields one of its labels.

Authors must use the UTF-8 encoding and must use its (ASCII case-insensitive) "utf-8" label to identify it.

New protocols and formats, as well as existing formats deployed in new contexts, must use the UTF-8 encoding exclusively. If these protocols and formats need to expose the encoding’s name or label, they must expose it as "utf-8".

This is a more basic and restrictive algorithm of mapping labels to encodings than section 1.4 of Unicode Technical Standard #22 prescribes, as that is necessary to be compatible with deployed content.

All encodings and their labels are also available as non-normative encodings.json resource.

The set of supported encodings is primarily based on the intersection of the sets supported by major browser engines when the development of this standard started, while removing encodings that were rarely used legitimately but that could be used in attacks. The inclusion of some encodings is questionable in the light of anecdotal evidence of the level of use by existing Web content. That is, while they have been broadly supported by browsers, it is unclear if they are broadly used by Web content. However, an effort has not been made to eagerly remove single-byte encodings that were broadly supported by browsers or are part of the ISO 8859 series. In particular, the necessity of the inclusion of IBM866, macintosh, x-mac-cyrillic, ISO-8859-3, ISO-8859-10, ISO-8859-14, and ISO-8859-16 is doubtful for the purpose of supporting existing content, but there are no plans to remove these.

4.3. Output encodings

To get an output encoding from an encoding encoding:

1. If encoding is replacement or UTF-16BE/LE, then return UTF-8.

2. Return encoding.

The get an output encoding algorithm is useful for URL parsing and HTML form submission, which both need exactly this.

5. Indexes

Most legacy encodings make use of an index. An index is an ordered list of entries, each entry consisting of a pointer and a corresponding code point. Within an index pointers are unique and code points can be duplicated.

An efficient implementation likely has two indexes per encoding. One optimized for its decoder and one for its encoder.

To find the pointers and their corresponding code points in an index, let lines be the result of splitting the resource’s contents on U+000A LF. Then remove each item in lines 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 lines on U+0009 TAB. 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.

To signify changes an index includes an Identifier and a Date. If an Identifier has changed, so has the index.

The index code point for pointer in index is the code point corresponding to pointer in index, or null if pointer is not in index.

The index pointer for codePoint in index is the first pointer corresponding to codePoint in index, or null if codePoint is not in index.

These are the indexes defined by this specification, excluding index single-byte, which have their own table:

All indexes are also available as a non-normative indexes.json resource. (Index gb18030 ranges has a slightly different format here, to be able to represent ranges.)

6. Hooks for standards

6.1. Legacy hooks for standards

7. API

This section uses terminology from Web IDL. Browser user agents must support this API. JavaScript implementations should support this API. Other user agents or programming languages are encouraged to use an API suitable to their needs, which might not be this one. [WEBIDL]

function encodeArrayOfStrings(strings) {
  var encoder, encoded, len, bytes, view, offset;

  encoder = new TextEncoder();
  encoded = [];

  len = Uint32Array.BYTES_PER_ELEMENT;
  for (var i = 0; i < strings.length; i++) {
    len += Uint32Array.BYTES_PER_ELEMENT;
    encoded[i] = encoder.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 (var 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;
}

function decodeArrayOfStrings(buffer, encoding) {
  var decoder, view, offset, num_strings, strings, len;

  decoder = new TextDecoder(encoding);
  view = new DataView(buffer);
  offset = 0;
  strings = [];

  num_strings = view.getUint32(offset);
  offset += Uint32Array.BYTES_PER_ELEMENT;
  for (var i = 0; i < num_strings; i++) {
    len = view.getUint32(offset);
    offset += Uint32Array.BYTES_PER_ELEMENT;
    strings[i] = decoder.decode(
      new DataView(view.buffer, offset, len));
    offset += len;
  }
  return strings;
}

7.1. Interface mixin TextDecoderCommon

interface mixin TextDecoderCommon {
  readonly attribute DOMString encoding;
  readonly attribute boolean fatal;
  readonly attribute boolean ignoreBOM;
};

The TextDecoderCommon interface mixin defines common getters that are shared between TextDecoder and TextDecoderStream objects. These objects have an associated:

encoding

An encoding.

decoder

A decoder instance.

I/O queue

An I/O queue of bytes.

ignore BOM

A boolean, initially false.

BOM seen

A boolean, initially false.

error mode

An error mode, initially "replacement".

7.2. Interface TextDecoder

dictionary TextDecoderOptions {
  boolean fatal = false;
  boolean ignoreBOM = false;
};

dictionary TextDecodeOptions {
  boolean stream = false;
};

[Exposed=*]
interface TextDecoder {
  constructor(optional DOMString label = "utf-8", optional TextDecoderOptions options = {});

  USVString decode(optional AllowSharedBufferSource input, optional TextDecodeOptions options = {});
};
TextDecoder includes TextDecoderCommon;

A TextDecoder object has an associated do not flush, which is a boolean, initially false.

decoder = new TextDecoder([label = "utf-8" [, options]])

Returns a new TextDecoder object.

If label is either not a label or is a label for replacement, throws a RangeError.

decoder . encoding

Returns encoding’s name, lowercased.

decoder . fatal

Returns true if error mode is "fatal"; otherwise false.

decoder . ignoreBOM

Returns the value of ignore BOM.

decoder . decode([input [, options]])

Returns the result of running encoding’s decoder. The method can be invoked zero or more times with options’s stream set to true, and then once without options’s stream (or set to false), to process a fragmented input. If the invocation without options’s stream (or set to false) has no input, it’s clearest to omit both arguments.

var string = "", decoder = new TextDecoder(encoding), buffer;
while(buffer = next_chunk()) {
  string += decoder.decode(buffer, {stream:true});
}
string += decoder.decode(); // end-of-queue

If the error mode is "fatal" and encoding’s decoder returns error, throws a TypeError.

7.3. Interface mixin TextEncoderCommon

interface mixin TextEncoderCommon {
  readonly attribute DOMString encoding;
};

The TextEncoderCommon interface mixin defines common getters that are shared between TextEncoder and TextEncoderStream objects.

7.4. Interface TextEncoder

dictionary TextEncoderEncodeIntoResult {
  unsigned long long read;
  unsigned long long written;
};

[Exposed=*]
interface TextEncoder {
  constructor();

  [NewObject] Uint8Array encode(optional USVString input = "");
  TextEncoderEncodeIntoResult encodeInto(USVString source, [AllowShared] Uint8Array destination);
};
TextEncoder includes TextEncoderCommon;

A TextEncoder object offers no label argument as it only supports UTF-8. It also offers no stream option as no encoder requires buffering of scalar values.

encoder = new TextEncoder()

Returns a new TextEncoder object.

encoder . encoding

Returns "utf-8".

encoder . encode([input = ""])

Returns the result of running UTF-8’s encoder.

encoder . encodeInto(source, destination)

Runs the UTF-8 encoder on source, stores the result of that operation into destination, and returns the progress made as an object wherein read is the number of converted code units of source and written is the number of bytes modified in destination.

function convertString(buffer, input, callback) {
  let bufferSize = 256,
      bufferStart = malloc(buffer, bufferSize),
      writeOffset = 0,
      readOffset = 0;
  while (true) {
    const view = new Uint8Array(buffer, bufferStart + writeOffset, bufferSize - writeOffset),
          {read, written} = cachedEncoder.encodeInto(input.substring(readOffset), view);
    readOffset += read;
    writeOffset += written;
    if (readOffset === input.length) {
      callback(bufferStart, writeOffset);
      free(buffer, bufferStart);
      return;
    }
    bufferSize *= 2;
    bufferStart = realloc(buffer, bufferStart, bufferSize);
  }
}

7.5. Interface TextDecoderStream

[Exposed=*]
interface TextDecoderStream {
  constructor(optional DOMString label = "utf-8", optional TextDecoderOptions options = {});
};
TextDecoderStream includes TextDecoderCommon;
TextDecoderStream includes GenericTransformStream;

decoder = new TextDecoderStream([label = "utf-8" [, options]])

Returns a new TextDecoderStream object.

If label is either not a label or is a label for replacement, throws a RangeError.

decoder . encoding

Returns encoding’s name, lowercased.

decoder . fatal

Returns true if error mode is "fatal", and false otherwise.

decoder . ignoreBOM

Returns the value of ignore BOM.

decoder . readable

Returns a readable stream whose chunks are strings resulting from running encoding’s decoder on the chunks written to writable.

decoder . writable

Returns a writable stream which accepts AllowSharedBufferSource chunks and runs them through encoding’s decoder before making them available to readable.

Typically this will be used via the pipeThrough() method on a ReadableStream source.

var decoder = new TextDecoderStream(encoding);
byteReadable
  .pipeThrough(decoder)
  .pipeTo(textWritable);

If the error mode is "fatal" and encoding’s decoder returns error, both readable and writable will be errored with a TypeError.

7.6. Interface TextEncoderStream

[Exposed=*]
interface TextEncoderStream {
  constructor();
};
TextEncoderStream includes TextEncoderCommon;
TextEncoderStream includes GenericTransformStream;

A TextEncoderStream object has an associated:

encoder

An encoder instance.

leading surrogate

Null or a leading surrogate, initially null.

A TextEncoderStream object offers no label argument as it only supports UTF-8.

encoder = new TextEncoderStream()

Returns a new TextEncoderStream object.

encoder . encoding

Returns "utf-8".

encoder . readable

Returns a readable stream whose chunks are Uint8Arrays resulting from running UTF-8’s encoder on the chunks written to writable.

encoder . writable

Returns a writable stream which accepts string chunks and runs them through UTF-8’s encoder before making them available to readable.

Typically this will be used via the pipeThrough() method on a ReadableStream source.

textReadable
  .pipeThrough(new TextEncoderStream())
  .pipeTo(byteWritable);

8. The encoding

8.1. UTF-8

8.1.1. UTF-8 decoder

A byte order mark has priority over a label as it has been found to be more accurate in deployed content. Therefore it is not part of the UTF-8 decoder algorithm, but rather the decode and UTF-8 decode algorithms.

UTF-8’s decoder has an associated:

UTF-8 code point

UTF-8 bytes seen

UTF-8 bytes needed

Each a number, initially 0.

UTF-8 lower boundary

A byte, initially 0x80.

UTF-8 upper boundary

A byte, initially 0xBF.

UTF-8’s decoder’s handler, given ioQueue and byte, runs these steps:

1. If byte is end-of-queue and UTF-8 bytes needed is not 0, then set UTF-8 bytes needed to 0 and return error.

2. If byte is end-of-queue, then return finished.

3. If UTF-8 bytes needed is 0, based on byte:

   0x00 to 0x7F

   Return a code point whose value is byte.

   0xC2 to 0xDF

   1. Set UTF-8 bytes needed to 1.

   2. Set UTF-8 code point to byte & 0x1F.

      The five least significant bits of byte.

   0xE0 to 0xEF

   1. If byte is 0xE0, then set UTF-8 lower boundary to 0xA0.

   2. If byte is 0xED, then set UTF-8 upper boundary to 0x9F.

   3. Set UTF-8 bytes needed to 2.

   4. Set UTF-8 code point to byte & 0xF.

      The four least significant bits of byte.

   0xF0 to 0xF4

   1. If byte is 0xF0, then set UTF-8 lower boundary to 0x90.

   2. If byte is 0xF4, then set UTF-8 upper boundary to 0x8F.

   3. Set UTF-8 bytes needed to 3.

   4. Set UTF-8 code point to byte & 0x7.

      The three least significant bits of byte.

   Otherwise

   Return error.

   Return continue.

4. If byte is not in the range UTF-8 lower boundary to UTF-8 upper boundary, inclusive:

   1. Set UTF-8 code point, UTF-8 bytes needed, and UTF-8 bytes seen to 0, set UTF-8 lower boundary to 0x80, and set UTF-8 upper boundary to 0xBF.

   2. Restore byte to ioQueue.

   3. Return error.

5. Set UTF-8 lower boundary to 0x80 and UTF-8 upper boundary to 0xBF.

6. Set UTF-8 code point to (UTF-8 code point << 6) | (byte & 0x3F)

   Shift the existing bits of UTF-8 code point left by six places and set the newly-vacated six least significant bits to the six least significant bits of byte.

7. Increase UTF-8 bytes seen by one.

8. If UTF-8 bytes seen is not equal to UTF-8 bytes needed, then return continue.

9. Let codePoint be UTF-8 code point.

10. Set UTF-8 code point, UTF-8 bytes needed, and UTF-8 bytes seen to 0.

11. Return a code point whose value is codePoint.

The constraints in the UTF-8 decoder above match “Best Practices for Using U+FFFD” from the Unicode standard. No other behavior is permitted per the Encoding Standard (other algorithms that achieve the same result are fine, even encouraged). [UNICODE]

8.1.2. UTF-8 encoder

UTF-8’s encoder’s handler, given unused and codePoint, runs these steps:

1. If codePoint is end-of-queue, then return finished.

2. If codePoint is an ASCII code point, then return a byte whose value is codePoint.

3. Set count and offset based on the range codePoint is in:

   U+0080 to U+07FF, inclusive

   1 and 0xC0

   U+0800 to U+FFFF, inclusive

   2 and 0xE0

   U+10000 to U+10FFFF, inclusive

   3 and 0xF0

4. Let bytes be a byte sequence whose first byte is (codePoint >> (6 × count)) + offset.

5. While count is greater than 0:

   1. Set temp to codePoint >> (6 × (count − 1)).

   2. Append to bytes 0x80 | (temp & 0x3F).

   3. Decrease count by one.

6. Return bytes bytes, in order.

This algorithm has identical results to the one described in the Unicode standard. It is included here for completeness. [UNICODE]

9. Legacy single-byte encodings

An encoding where each byte is either a single code point or nothing, is a single-byte encoding. Single-byte encodings share the decoder and encoder. Index single-byte, as referenced by the single-byte decoder and single-byte encoder, is defined by the following table, and depends on the single-byte encoding in use. All but two single-byte encodings have a unique index.

ISO-8859-8 and ISO-8859-8-I are distinct encoding names, because ISO-8859-8 has influence on the layout direction. And although historically this might have been the case for ISO-8859-6 and "ISO-8859-6-I" as well, that is no longer true.

9.1. single-byte decoder

Single-byte encodings’s decoder’s handler, given unused and byte, runs these steps:

1. If byte is end-of-queue, then return finished.

2. If byte is an ASCII byte, then return a code point whose value is byte.

3. Let codePoint be the index code point for byte − 0x80 in index single-byte.

4. If codePoint is null, then return error.

5. Return a code point whose value is codePoint.

9.2. single-byte encoder

Single-byte encodings’s encoder’s handler, given unused and codePoint, runs these steps:

1. If codePoint is end-of-queue, then return finished.

2. If codePoint is an ASCII code point, then return a byte whose value is codePoint.

3. Let pointer be the index pointer for codePoint in index single-byte.

4. If pointer is null, then return error with codePoint.

5. Return a byte whose value is pointer + 0x80.

10. Legacy multi-byte Chinese (simplified) encodings

10.1. GBK

10.1.1. GBK decoder

GBK’s decoder is gb18030’s decoder.

10.1.2. GBK encoder

GBK’s encoder is gb18030’s encoder with its is GBK set to true.

Not fully aliasing GBK with gb18030 is a conservative move to decrease the chances of breaking legacy servers and other consumers of content generated with GBK’s encoder.

10.2. gb18030

10.2.1. gb18030 decoder

gb18030’s decoder has an associated:

gb18030 first

gb18030 second

gb18030 third

Each a byte, initially 0x00.

gb18030’s decoder’s handler, given ioQueue and byte, runs these steps:

1. If byte is end-of-queue and gb18030 first, gb18030 second, and gb18030 third are 0x00, then return finished.

2. If byte is end-of-queue, and gb18030 first, gb18030 second, or gb18030 third is not 0x00, then set gb18030 first, gb18030 second, and gb18030 third to 0x00, and return error.

3. If gb18030 third is not 0x00:

   1. If byte is not in the range 0x30 to 0x39, inclusive:

      1. Restore « gb18030 second, gb18030 third, byte » to ioQueue.

      2. Set gb18030 first, gb18030 second, and gb18030 third to 0x00.

      3. Return error.

   2. Let codePoint be the index gb18030 ranges code point for ((gb18030 first − 0x81) × (10 × 126 × 10)) + ((gb18030 second − 0x30) × (10 × 126)) + ((gb18030 third − 0x81) × 10) + byte − 0x30.

   3. Set gb18030 first, gb18030 second, and gb18030 third to 0x00.

   4. If codePoint is null, then return error.

   5. Return a code point whose value is codePoint.

4. If gb18030 second is not 0x00:

   1. If byte is in the range 0x81 to 0xFE, inclusive, then set gb18030 third to byte and return continue.

   2. Restore « gb18030 second, byte » to ioQueue, set gb18030 first and gb18030 second to 0x00, and return error.

5. If gb18030 first is not 0x00:

   1. If byte is in the range 0x30 to 0x39, inclusive, then set gb18030 second to byte and return continue.

   2. Let leading be gb18030 first.

   3. Set gb18030 first to 0x00.

   4. Let pointer be null.

   5. Let offset be 0x40 if byte is less than 0x7F; otherwise 0x41.

   6. If byte is in the range 0x40 to 0x7E, inclusive, or 0x80 to 0xFE, inclusive, then set pointer to (leading − 0x81) × 190 + (byte − offset).

   7. Let codePoint be null if pointer is null; otherwise the index code point for pointer in index gb18030.

   8. If codePoint is non-null, then return a code point whose value is codePoint.

   9. If byte is an ASCII byte, then restore byte to ioQueue.

   10. Return error.

6. If byte is an ASCII byte, then return a code point whose value is byte.

7. If byte is 0x80, then return code point U+20AC (€).

8. If byte is in the range 0x81 to 0xFE, inclusive, then set gb18030 first to byte and return continue.

9. Return error.

10.2.2. gb18030 encoder

gb18030’s encoder has an associated is GBK, which is a boolean, initially false.

gb18030’s encoder’s handler, given unused and codePoint, runs these steps:

1. If codePoint is end-of-queue, then return finished.

2. If codePoint is an ASCII code point, then return a byte whose value is codePoint.

3. If codePoint is U+E5E5, then return error with codePoint.

   Index gb18030 maps 0xA3 0xA0 to U+3000 IDEOGRAPHIC SPACE rather than U+E5E5 for compatibility with deployed content. Therefore it cannot roundtrip.

4. If is GBK is true and codePoint is U+20AC (€), then return byte 0x80.

5. If there is a row in the table below whose first column is codePoint, then return the two bytes on the same row listed in the second column:

   Code point	Bytes
   U+E78D	0xA6 0xD9
   U+E78E	0xA6 0xDA
   U+E78F	0xA6 0xDB
   U+E790	0xA6 0xDC
   U+E791	0xA6 0xDD
   U+E792	0xA6 0xDE
   U+E793	0xA6 0xDF
   U+E794	0xA6 0xEC
   U+E795	0xA6 0xED
   U+E796	0xA6 0xF3
   U+E81E	0xFE 0x59
   U+E826	0xFE 0x61
   U+E82B	0xFE 0x66
   U+E82C	0xFE 0x67
   U+E832	0xFE 0x6D
   U+E843	0xFE 0x7E
   U+E854	0xFE 0x90
   U+E864	0xFE 0xA0

   This asymmetric encoder table preserves compatibility with the GB18030-2005 standard. See also the explanation at index gb18030 ranges.

6. Let pointer be the index pointer for codePoint in index gb18030.

7. If pointer is non-null:

   1. Let leading be pointer / 190 + 0x81.

   2. Let trailing be pointer % 190.

   3. Let offset be 0x40 if trailing is less than 0x3F, otherwise 0x41.

   4. Return two bytes whose values are leading and trailing + offset.

8. If is GBK is true, then return error with codePoint.

9. Set pointer to the index gb18030 ranges pointer for codePoint.

10. Let byte1 be pointer / (10 × 126 × 10).

11. Set pointer to pointer % (10 × 126 × 10).

12. Let byte2 be pointer / (10 × 126).

13. Set pointer to pointer % (10 × 126).

14. Let byte3 be pointer / 10.

15. Let byte4 be pointer % 10.

16. Return four bytes whose values are byte1 + 0x81, byte2 + 0x30, byte3 + 0x81, byte4 + 0x30.

11. Legacy multi-byte Chinese (traditional) encodings

11.1. Big5

11.1.1. Big5 decoder

Big5’s decoder has an associated Big5 leading, which is a byte, initially 0x00.

Big5’s decoder’s handler, given ioQueue and byte, runs these steps:

1. If byte is end-of-queue and Big5 leading is not 0x00, then set Big5 leading to 0x00 and return error.

2. If byte is end-of-queue and Big5 leading is 0x00, then return finished.

3. If Big5 leading is not 0x00:

   1. Let leading be Big5 leading.

   2. Set Big5 leading to 0x00.

   3. Let pointer be null.

   4. Let offset be 0x40 if byte is less than 0x7F; otherwise 0x62.

   5. If byte is in the range 0x40 to 0x7E, inclusive, or 0xA1 to 0xFE, inclusive, then set pointer to (leading − 0x81) × 157 + (byte − offset).

   6. If there is a row in the table below whose first column is pointer, then return the two code points listed in its second column (the third column is irrelevant):

      Pointer	Code points	Notes
      1133	U+00CA U+0304	Ê̄ (LATIN CAPITAL LETTER E WITH CIRCUMFLEX AND MACRON)
      1135	U+00CA U+030C	Ê̌ (LATIN CAPITAL LETTER E WITH CIRCUMFLEX AND CARON)
      1164	U+00EA U+0304	ê̄ (LATIN SMALL LETTER E WITH CIRCUMFLEX AND MACRON)
      1166	U+00EA U+030C	ê̌ (LATIN SMALL LETTER E WITH CIRCUMFLEX AND CARON)

      Since indexes are limited to single code points this table is used for these pointers.

   7. Let codePoint be null if pointer is null; otherwise the index code point for pointer in index Big5.

   8. If codePoint is non-null, then return a code point whose value is codePoint.

   9. If byte is an ASCII byte, restore byte to ioQueue.

   10. Return error.

4. If byte is an ASCII byte, then return a code point whose value is byte.

5. If byte is in the range 0x81 to 0xFE, inclusive, then set Big5 leading to byte and return continue.

6. Return error.

11.1.2. Big5 encoder

Big5’s encoder’s handler, given unused and codePoint, runs these steps:

1. If codePoint is end-of-queue, then return finished.

2. If codePoint is an ASCII code point, then return a byte whose value is codePoint.

3. Let pointer be the index Big5 pointer for codePoint.

4. If pointer is null, then return error with codePoint.

5. Let leading be pointer / 157 + 0x81.

6. Let trailing be pointer % 157.

7. Let offset be 0x40 if trailing is less than 0x3F, otherwise 0x62.

8. Return two bytes whose values are leading and trailing + offset.

12. Legacy multi-byte Japanese encodings

12.1. EUC-JP

12.1.1. EUC-JP decoder

EUC-JP’s decoder has an associated:

EUC-JP jis0212

A boolean, initially false.

EUC-JP leading

A byte, initially 0x00.

EUC-JP’s decoder’s handler, given ioQueue and byte, runs these steps:

1. If byte is end-of-queue and EUC-JP leading is not 0x00, then set EUC-JP leading to 0x00 and return error.

2. If byte is end-of-queue and EUC-JP leading is 0x00, then return finished.

3. If EUC-JP leading is 0x8E and byte is in the range 0xA1 to 0xDF, inclusive, then set EUC-JP leading to 0x00 and return a code point whose value is 0xFF61 − 0xA1 + byte.

4. If EUC-JP leading is 0x8F and byte is in the range 0xA1 to 0xFE, inclusive, then set EUC-JP jis0212 to true, set EUC-JP leading to byte, and return continue.

5. If EUC-JP leading is not 0x00:

   1. Let leading be EUC-JP leading.

   2. Set EUC-JP leading to 0x00.

   3. Let codePoint be null.

   4. If leading and byte are both in the range 0xA1 to 0xFE, inclusive, then set codePoint to the index code point for (leading − 0xA1) × 94 + byte − 0xA1 in index jis0208 if EUC-JP jis0212 is false and in index jis0212 otherwise.

   5. Set EUC-JP jis0212 to false.

   6. If codePoint is non-null, then return a code point whose value is codePoint.

   7. If byte is an ASCII byte, then restore byte to ioQueue.

   8. Return error.

6. If byte is an ASCII byte, then return a code point whose value is byte.

7. If byte is 0x8E, 0x8F, or in the range 0xA1 to 0xFE, inclusive, then set EUC-JP leading to byte and return continue.

8. Return error.

12.1.2. EUC-JP encoder

EUC-JP’s encoder’s handler, given unused and codePoint, runs these steps:

1. If codePoint is end-of-queue, then return finished.

2. If codePoint is an ASCII code point, then return a byte whose value is codePoint.

3. If codePoint is U+00A5 (¥), then return byte 0x5C.

4. If codePoint is U+203E (‾), then return byte 0x7E.

5. If codePoint is in the range U+FF61 (｡) to U+FF9F (ﾟ), inclusive, then return two bytes whose values are 0x8E and codePoint − 0xFF61 + 0xA1.

6. If codePoint is U+2212 (−), then set it to U+FF0D (－).

7. Let pointer be the index pointer for codePoint in index jis0208.

   If pointer is non-null, it is less than 8836 due to the nature of index jis0208 and the index pointer operation.

8. If pointer is null, then return error with codePoint.

9. Let leading be pointer / 94 + 0xA1.

10. Let trailing be pointer % 94 + 0xA1.

11. Return two bytes whose values are leading and trailing.

12.2. ISO-2022-JP

12.2.1. ISO-2022-JP decoder

ISO-2022-JP’s decoder has an associated:

ISO-2022-JP decoder state

A state, initially ASCII.

ISO-2022-JP decoder output state

A state, initially ASCII.

ISO-2022-JP leading

A byte, initially 0x00.

ISO-2022-JP output

A boolean, initially false.

ISO-2022-JP’s decoder’s handler, given ioQueue and byte, runs these steps, switching on ISO-2022-JP decoder state:

ASCII

Based on byte:

0x1B

Set ISO-2022-JP decoder state to escape start and return continue.

0x00 to 0x7F, excluding 0x0E, 0x0F, and 0x1B

Set ISO-2022-JP output to false and return a code point whose value is byte.

end-of-queue

Return finished.

Otherwise

Set ISO-2022-JP output to false and return error.

Roman

Based on byte:

0x1B

Set ISO-2022-JP decoder state to escape start and return continue.

0x5C

Set ISO-2022-JP output to false and return code point U+00A5 (¥).

0x7E

Set ISO-2022-JP output to false and return code point U+203E (‾).

0x00 to 0x7F, excluding 0x0E, 0x0F, 0x1B, 0x5C, and 0x7E

Set ISO-2022-JP output to false and return a code point whose value is byte.

end-of-queue

Return finished.

Otherwise

Set ISO-2022-JP output to false and return error.

katakana

Based on byte:

0x1B

Set ISO-2022-JP decoder state to escape start and return continue.

0x21 to 0x5F

Set ISO-2022-JP output to false and return a code point whose value is 0xFF61 − 0x21 + byte.

end-of-queue

Return finished.

Otherwise

Set ISO-2022-JP output to false and return error.

Leading byte

Based on byte:

0x1B

Set ISO-2022-JP decoder state to escape start and return continue.

0x21 to 0x7E

Set ISO-2022-JP output to false, ISO-2022-JP leading to byte, ISO-2022-JP decoder state to trailing byte, and return continue.

end-of-queue

Return finished.

Otherwise

Set ISO-2022-JP output to false and return error.

Trailing byte

Based on byte:

0x1B

Set ISO-2022-JP decoder state to escape start and return error.

0x21 to 0x7E

1. Set the ISO-2022-JP decoder state to leading byte.

2. Let pointer be (ISO-2022-JP leading − 0x21) × 94 + byte − 0x21.

3. Let codePoint be the index code point for pointer in index jis0208.

4. If codePoint is null, then return error.

5. Return a code point whose value is codePoint.

end-of-queue

Set the ISO-2022-JP decoder state to leading byte and return error.

Otherwise

Set ISO-2022-JP decoder state to leading byte and return error.

Escape start

1. If byte is either 0x24 or 0x28, then set ISO-2022-JP leading to byte, ISO-2022-JP decoder state to escape, and return continue.

2. If byte is not end-of-queue, then restore byte to ioQueue.

3. Set ISO-2022-JP output to false, ISO-2022-JP decoder state to ISO-2022-JP decoder output state, and return error.

Escape

1. Let leading be ISO-2022-JP leading and set ISO-2022-JP leading to 0x00.

2. Let state be null.

3. If leading is 0x28 and byte is 0x42, then set state to ASCII.

4. If leading is 0x28 and byte is 0x4A, then set state to Roman.

5. If leading is 0x28 and byte is 0x49, then set state to katakana.

6. If leading is 0x24 and byte is either 0x40 or 0x42, then set state to leading byte.

7. If state is non-null:

   1. Set ISO-2022-JP decoder state and ISO-2022-JP decoder output state to state.

   2. Let output be the value of ISO-2022-JP output.

   3. Set ISO-2022-JP output to true.

   4. Return continue, if output is false, and error otherwise.

8. If byte is end-of-queue, then restore leading to ioQueue; otherwise, restore « leading, byte » to ioQueue.

9. Set ISO-2022-JP output to false, ISO-2022-JP decoder state to ISO-2022-JP decoder output state and return error.

12.2.2. ISO-2022-JP encoder

ISO-2022-JP’s encoder has an associated ISO-2022-JP encoder state which is ASCII, Roman, or jis0208, initially ASCII.

ISO-2022-JP’s encoder’s handler, given ioQueue and codePoint, runs these steps:

1. If codePoint is end-of-queue and ISO-2022-JP encoder state is not ASCII, then set ISO-2022-JP encoder state to ASCII and return three bytes 0x1B 0x28 0x42.

2. If codePoint is end-of-queue and ISO-2022-JP encoder state is ASCII, then return finished.

3. If ISO-2022-JP encoder state is ASCII or Roman, and codePoint is U+000E, U+000F, or U+001B, then return error with U+FFFD (�).

   This returns U+FFFD (�) rather than codePoint to prevent attacks.

4. If ISO-2022-JP encoder state is ASCII and codePoint is an ASCII code point, then return a byte whose value is codePoint.

5. If ISO-2022-JP encoder state is Roman and codePoint is an ASCII code point, excluding U+005C (\) and U+007E (~), or is U+00A5 (¥) or U+203E (‾):

   1. If codePoint is an ASCII code point, then return a byte whose value is codePoint.

   2. If codePoint is U+00A5 (¥), then return byte 0x5C.

   3. If codePoint is U+203E (‾), then return byte 0x7E.

6. If codePoint is an ASCII code point, and ISO-2022-JP encoder state is not ASCII, then restore codePoint to ioQueue, set ISO-2022-JP encoder state to ASCII, and return three bytes 0x1B 0x28 0x42.

7. If codePoint is either U+00A5 (¥) or U+203E (‾), and ISO-2022-JP encoder state is not Roman, then restore codePoint to ioQueue, set ISO-2022-JP encoder state to Roman, and return three bytes 0x1B 0x28 0x4A.

8. If codePoint is U+2212 (−), then set it to U+FF0D (－).

9. If codePoint is in the range U+FF61 (｡) to U+FF9F (ﾟ), inclusive, then set it to the index code point for codePoint − 0xFF61 in index ISO-2022-JP katakana.

10. Let pointer be the index pointer for codePoint in index jis0208.

    If pointer is non-null, it is less than 8836 due to the nature of index jis0208 and the index pointer operation.

11. If pointer is null:

    1. If ISO-2022-JP encoder state is jis0208, then restore codePoint to ioQueue, set ISO-2022-JP encoder state to ASCII, and return three bytes 0x1B 0x28 0x42.

    2. Return error with codePoint.

12. If ISO-2022-JP encoder state is not jis0208, then restore codePoint to ioQueue, set ISO-2022-JP encoder state to jis0208, and return three bytes 0x1B 0x24 0x42.

13. Let leading be pointer / 94 + 0x21.

14. Let trailing be pointer % 94 + 0x21.

15. Return two bytes whose values are leading and trailing.

12.3. Shift_JIS

12.3.1. Shift_JIS decoder

Shift_JIS’s decoder has an associated Shift_JIS leading, which is a byte, initially 0x00.

Shift_JIS’s decoder’s handler, given ioQueue and byte, runs these steps:

1. If byte is end-of-queue and Shift_JIS leading is not 0x00, then set Shift_JIS leading to 0x00 and return error.

2. If byte is end-of-queue and Shift_JIS leading is 0x00, then return finished.

3. If Shift_JIS leading is not 0x00:

   1. Let leading be Shift_JIS leading.

   2. Set Shift_JIS leading to 0x00.

   3. Let pointer be null.

   4. Let offset be 0x40 if byte is less than 0x7F; otherwise 0x41.

   5. Let leadingOffset be 0x81 if leading is less than 0xA0; otherwise 0xC1.

   6. If byte is in the range 0x40 to 0x7E, inclusive, or 0x80 to 0xFC, inclusive, then set pointer to (leading − leadingOffset) × 188 + byte − offset.

   7. If pointer is in the range 8836 to 10715, inclusive, then return a code point whose value is 0xE000 − 8836 + pointer.

      This is interoperable legacy from Windows known as EUDC.

   8. Let codePoint be null if pointer is null; otherwise the index code point for pointer in index jis0208.

   9. If codePoint is non-null, then return a code point whose value is codePoint.

   10. If byte is an ASCII byte, then restore byte to ioQueue.

   11. Return error.

4. If byte is an ASCII byte or 0x80, then return a code point whose value is byte.

5. If byte is in the range 0xA1 to 0xDF, inclusive, then return a code point whose value is 0xFF61 − 0xA1 + byte.

6. If byte is in the range 0x81 to 0x9F, inclusive, or 0xE0 to 0xFC, inclusive, then set Shift_JIS leading to byte and return continue.

7. Return error.

12.3.2. Shift_JIS encoder

Shift_JIS’s encoder’s handler, given unused and codePoint, runs these steps:

1. If codePoint is end-of-queue, then return finished.

2. If codePoint is an ASCII code point or U+0080, then return a byte whose value is codePoint.

3. If codePoint is U+00A5 (¥), then return byte 0x5C.

4. If codePoint is U+203E (‾), then return byte 0x7E.

5. If codePoint is in the range U+FF61 (｡) to U+FF9F (ﾟ), inclusive, then return a byte whose value is codePoint − 0xFF61 + 0xA1.

6. If codePoint is U+2212 (−), then set it to U+FF0D (－).

7. Let pointer be the index Shift_JIS pointer for codePoint.

8. If pointer is null, then return error with codePoint.

9. Let leading be pointer / 188.

10. Let leadingOffset be 0x81 if leading is less than 0x1F; otherwise 0xC1.

11. Let trailing be pointer % 188.

12. Let offset be 0x40 if trailing is less than 0x3F; otherwise 0x41.

13. Return two bytes whose values are leading + leadingOffset and trailing + offset.

13. Legacy multi-byte Korean encodings

13.1. EUC-KR

13.1.1. EUC-KR decoder

EUC-KR’s decoder has an associated EUC-KR leading, which is a byte, initially 0x00.

EUC-KR’s decoder’s handler, given ioQueue and byte, runs these steps:

1. If byte is end-of-queue and EUC-KR leading is not 0x00, then set EUC-KR leading to 0x00 and return error.

2. If byte is end-of-queue and EUC-KR leading is 0x00, then return finished.

3. If EUC-KR leading is not 0x00:

   1. Let leading be EUC-KR leading.

   2. Set EUC-KR leading to 0x00.

   3. Let pointer be null.

   4. If byte is in the range 0x41 to 0xFE, inclusive, then set pointer to (leading − 0x81) × 190 + (byte − 0x41).

   5. Let codePoint be null if pointer is null; otherwise the index code point for pointer in index EUC-KR.

   6. If codePoint is non-null, then return a code point whose value is codePoint.

   7. If byte is an ASCII byte, then restore byte to ioQueue.

   8. Return error.

4. If byte is an ASCII byte, then return a code point whose value is byte.

5. If byte is in the range 0x81 to 0xFE, inclusive, then set EUC-KR leading to byte and return continue.

6. Return error.

13.1.2. EUC-KR encoder

EUC-KR’s encoder’s handler, given unused and codePoint, runs these steps:

1. If codePoint is end-of-queue, then return finished.

2. If codePoint is an ASCII code point, then return a byte whose value is codePoint.

3. Let pointer be the index pointer for codePoint in index EUC-KR.

4. If pointer is null, then return error with codePoint.

5. Let leading be pointer / 190 + 0x81.

6. Let trailing be pointer % 190 + 0x41.

7. Return two bytes whose values are leading and trailing.

14. Legacy miscellaneous encodings

14.1. replacement

The replacement encoding exists to prevent certain attacks that abuse a mismatch between encodings supported on the server and the client.

14.1.1. replacement decoder

replacement’s decoder has an associated replacement error returned, which is a boolean, initially false.

replacement’s decoder’s handler, given unused and byte, runs these steps:

1. If byte is end-of-queue, then return finished.

2. If replacement error returned is false, then set replacement error returned to true and return error.

3. Return finished.

14.2. Common infrastructure for UTF-16BE/LE

UTF-16BE/LE is UTF-16BE or UTF-16LE.

14.2.1. shared UTF-16 decoder

A byte order mark has priority over a label as it has been found to be more accurate in deployed content. Therefore it is not part of the shared UTF-16 decoder algorithm, but rather the decode algorithm.

shared UTF-16 decoder has an associated:

UTF-16 leading byte

Null or a byte, initially null.

UTF-16 leading surrogate

Null or a leading surrogate, initially null.

is UTF-16BE decoder

A boolean, initially false.

shared UTF-16 decoder’s handler, given ioQueue and byte, runs these steps:

1. If byte is end-of-queue and either UTF-16 leading byte or UTF-16 leading surrogate is non-null, then set UTF-16 leading byte and UTF-16 leading surrogate to null, and return error.

2. If byte is end-of-queue and UTF-16 leading byte and UTF-16 leading surrogate are null, then return finished.

3. If UTF-16 leading byte is null, then set UTF-16 leading byte to byte and return continue.

4. Let codeUnit be the result of:

   is UTF-16BE decoder is true

   (UTF-16 leading byte << 8) + byte.

   is UTF-16BE decoder is false

   (byte << 8) + UTF-16 leading byte.

5. Set UTF-16 leading byte to null.

6. If UTF-16 leading surrogate is non-null:

   1. Let leadingSurrogate be UTF-16 leading surrogate.

   2. Set UTF-16 leading surrogate to null.

   3. If codeUnit is a trailing surrogate, then return a scalar value from surrogates given leadingSurrogate and codeUnit.

   4. Let byte1 be codeUnit >> 8.

   5. Let byte2 be codeUnit & 0x00FF.

   6. Let bytes be a list of two bytes whose values are byte1 and byte2, if is UTF-16BE decoder is true; otherwise byte2 and byte1.

   7. Restore bytes to ioQueue and return error.

7. If codeUnit is a leading surrogate, then set UTF-16 leading surrogate to codeUnit and return continue.

8. If codeUnit is a trailing surrogate, then return error.

9. Return code point codeUnit.

14.3. UTF-16BE

14.3.1. UTF-16BE decoder

UTF-16BE’s decoder is shared UTF-16 decoder with its is UTF-16BE decoder set to true.

14.4. UTF-16LE

"utf-16" is a label for UTF-16LE to deal with deployed content.

14.4.1. UTF-16LE decoder

UTF-16LE’s decoder is shared UTF-16 decoder.

14.5. x-user-defined

While technically this is a single-byte encoding, it is defined separately as it can be implemented algorithmically.

14.5.1. x-user-defined decoder

x-user-defined’s decoder’s handler, given unused and byte, runs these steps:

1. If byte is end-of-queue, then return finished.

2. If byte is an ASCII byte, then return a code point whose value is byte.

3. Return a code point whose value is 0xF780 + byte − 0x80.

14.5.2. x-user-defined encoder

x-user-defined’s encoder’s handler, given unused and codePoint, runs these steps:

1. If codePoint is end-of-queue, then return finished.

2. If codePoint is an ASCII code point, then return a byte whose value is codePoint.

3. If codePoint is in the range U+F780 to U+F7FF, inclusive, then return a byte whose value is codePoint − 0xF780 + 0x80.

4. Return error with codePoint.

15. Browser UI

Browsers are encouraged to not enable overriding the encoding of a resource. If such a feature is nonetheless present, browsers should not offer UTF-16BE/LE as an option, due to the aforementioned security issues. Browsers should also disable this feature if the resource was decoded using UTF-16BE/LE.

Implementation considerations

Instead of supporting I/O queues with arbitrary restore, the decoders for encodings in this standard could be implemented with:

1. The ability to unread the current byte.

2. A single-byte buffer for gb18030 (an ASCII byte) and ISO-2022-JP (0x24 or 0x28).

   For gb18030 when hitting a bogus byte while gb18030 third is not 0x00, gb18030 second could be moved into the single-byte buffer to be returned next, and gb18030 third would be the new gb18030 first, checked for not being 0x00 after the single-byte buffer was returned and emptied. This is possible as the range for the first and third byte in gb18030 is identical.

The ISO-2022-JP encoder needs ISO-2022-JP encoder state as additional state, but other than that, none of the encoders for encodings in this standard require additional state or buffers.

Acknowledgments

There have been a lot of people that have helped make encodings more interoperable over the years and thereby furthered the goals of this standard. Likewise many people have helped making this standard what it is today.

With that, many thanks to Adam Rice, Alan Chaney, Alexander Shtuchkin, Allen Wirfs-Brock, Andreu Botella, Aneesh Agrawal, Arkadiusz Michalski, Asmus Freytag, Ben Noordhuis, Bnaya Peretz, Boris Zbarsky, Bruno Haible, Cameron McCormack, Charles McCathieNeville, Christopher Foo, CodifierNL, David Carlisle, Domenic Denicola, Dominique Hazaël-Massieux, Doug Ewell, Erik van der Poel, 譚永鋒 (Frank Yung-Fong Tang), Glenn Maynard, Gordon P. Hemsley, Henri Sivonen, Ian Hickson, J. King, James Graham, Jeffrey Yasskin, John Tamplin, Joshua Bell, 村井純 (Jun Murai), 신정식 (Jungshik Shin), Jxck, 강 성훈 (Kang Seonghoon), 川幡太一 (Kawabata Taichi), Ken Lunde, Ken Whistler, Kenneth Russell, 田村健人 (Kent Tamura), Leif Halvard Silli, Luke Wagner, Maciej Hirsz, Makoto Kato, Mark Callow, Mark Crispin, Mark Davis, Martin Dürst, Masatoshi Kimura, Mattias Buelens, Ms2ger, Nigel Megitt, Nigel Tao, Norbert Lindenberg, Øistein E. Andersen, Peter Krefting, Philip Jägenstedt, Philip Taylor, Richard Ishida, Robbert Broersma, Robert Mustacchi, Ryan Dahl, Sam Sneddon, Shawn Steele, Simon Montagu, Simon Pieters, Simon Sapin, Stephen Checkoway, 寺田健 (Takeshi Terada), Vyacheslav Matva, Wolf Lammen, and 成瀬ゆい (Yui Naruse) for being awesome.

This standard is written by Anne van Kesteren (Apple, [email protected]). The API chapter was initially written by Joshua Bell (Google).

Intellectual property rights

Copyright © WHATWG (Apple, Google, Mozilla, Microsoft). This work is licensed under a Creative Commons Attribution 4.0 International License. To the extent portions of it are incorporated into source code, such portions in the source code are licensed under the BSD 3-Clause License instead.

This is the Living Standard. Those interested in the patent-review version should view the Living Standard Review Draft.