Half-width kana is not contained in ISO-2022-JP: it includes the Roman set of JIS X 0201, and all of JIS X 0208, but not the katakana set of JIS X 0201 (which is used for half-width kana in Shift JIS, for instance). Both sets of JIS X 0201 have ISO 2022 codes, but the ISO-2022-JP profile only includes the Roman set: this means that the format for including half-width katakana in ISO-2022-JP is both well-defined and a violation of the ISO-2022-JP format. For this reason, if half-width kana were accidentally included in a message, it could become garbled during transmission (see mojibake). The WHATWG encoding standard used by HTML5 permits decoding, but not encoding, of JIS X 0201 katakana in ISO-2022-JP as an extension to the format, and converts half-width katakana to their JIS X 0208 equivalents upon encoding.