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GB 18030

GB 18030 encoding layout. "Half codes" indicates codes used in pairs as four-byte codes.
MIME / IANA	GB18030
Alias(es)	Code page 54936
Language(s)	International, but primarily meant for Chinese
Standard	GB 18030-2022, GB 18030-2005, GB 18030-2000
Classification	Unicode Transformation Format, extended ASCII, variable-width encoding, CJK encoding
Extends	EUC-CN, GBK
Transforms / Encodes	ISO 10646 (Unicode)
Preceded by	GBK, GB2312
Not in the strictest sense of the term, as ASCII bytes can appear as trail bytes.
v t e

GB 18030 is a Chinese government standard, described as Information Technology — Chinese coded character set and defines the required language and character support necessary for software in China. GB18030 is the registered Internet name for the official character set of the People's Republic of China (PRC) superseding GB2312. As a Unicode Transformation Format (i.e. an encoding of all Unicode code points), GB18030 supports both simplified and traditional Chinese characters. It is also compatible with legacy encodings including GB/T 2312, CP936, and GBK 1.0.

The Unicode Consortium has warned implementers that the latest version of this Chinese standard, GB 18030-2022, introduces what they describe as "disruptive changes" from the previous version GB 18030-2005 "involving 33 different characters and 55 code positions". GB 18030-2022 was enforced from 1 August 2023. It has been implemented in ICU 73.2; and in Java 21, and backported to older Java 8, 11, 17 (LTS releases) and 20.0.2.

In addition to the encoding method, this standard contains requirements about which additional scripts and languages should be represented, and to whom this standard is applicable. This standard however does not define the official character forms for the Chinese characters; this is standardised in List of Commonly Used Standard Chinese Characters.

History

The GB18030 character set is formally called "Chinese National Standard GB 18030-2005: Information Technology—Chinese coded character set". GB abbreviates Guójiā Biāozhǔn (国家标准), which means national standard in Chinese. The standard was published by the China Standard Press, Beijing, 8 November 2005. Only a portion of the standard is mandatory. Since 1 May 2006, support for the mandatory subset is officially required for all software products sold in the PRC.

An older version of the standard, known as "Chinese National Standard GB 18030-2000: Information Technology—Chinese ideograms coded character set for information interchange—Extension for the basic set", was published on March 17, 2000. The encoding scheme stays the same in the new version, and the only difference in GB-to-Unicode mapping is that GB 18030-2000 mapped the character A8 BC (ḿ) to a private use code point U+E7C7, and character 81 35 F4 37 (without specifying any glyph) to U+1E3F (ḿ), whereas GB 18030-2005 swaps these two mapping assignments. More code points are now associated with characters due to update of Unicode, especially the appearance of CJK Unified Ideographs Extension B. Some characters used by ethnic minorities in China, such as Mongolian characters and Tibetan characters (GB 16959-1997 and GB/T 20542-2006), have been added as well, which accounts for the renaming of the standard.

Compared with its ancestors, GB 18030's mapping to Unicode has been modified for the 81 characters that were provisionally assigned a Unicode Private Use Area code point (U+E000–F8FF) in GBK 1.0 and that have later been encoded in Unicode. This is specified in Appendix E of GB 18030. There are 24 characters in GB 18030-2005 that are still mapped to Unicode PUA.

In the GB 18030-2022 update, the requirements for characters to be mapped to PUA has been lifted completely and all characters should be mapped to their standard Unicode codepoints. Of these, 18 mappings were updated by position-swapping similar to what happened between GBK and GB 18030. The remaining six kept the two-byte PUA mappings, so that a change to the 4-byte sequence is needed to follow the non-PUA preference.

As a national standard

The first version of GB 18030, designated GB 18030-2000 Information Technology—Chinese coded character set for information interchange — Extension for the basic set, consists of 1-byte and 2-byte encodings, together with 4-byte encoding for CJK Unified Ideographs Extension A matching those in Unicode 3.0. The corresponding Unicode code points of this subset, including provisional private assignments, lie entirely in the BMP. These parts are fully mandatory in GB 18030-2000. Most major computer companies had already standardized on some version of Unicode as the primary format for use in their binary formats and OS calls. However, they mostly had only supported code points in the BMP originally defined in Unicode 1.0, which supported only 65,536 codepoints and was often encoded in 16 bits as UCS-2. This standard is basically an extension based on GBK with additional characters in CJK Unified Ideographs Extension A.

The second version designated GB 18030-2005 Information Technology—Chinese coded character set has the same mandatory subset as GB 18030-2000 of 1-, 2- and 4-byte encodings. This version also includes the full CJK Unified Ideographs Extension B in the 4-byte encoding section which is outside the BMP as a suggestion support requirement. However, as the inclusion of CJK Unified Ideographs Extension B in a 4-byte region is required to be maintained during information processing, software can no longer get away with treating characters as 16-bit fixed width entities (UCS-2). Therefore, they must either process the data as a variable-width format (as with UTF-8 or UTF-16), which is the most common choice, or move to a larger fixed-width format (i.e. UTF-32). Microsoft made the change from UCS-2 to UTF-16 with Windows 2000. This version matches with Unicode 3.1, and also provided support for Hangul (Korean), Mongolian (including Manchu, Clear script, Sibe hergen, Galik), Tai Nuea, Tibetan, Uyghur/Kazakh/Kyrgyz and Yi.

The third and latest version, GB 18030-2022 Information Technology—Chinese coded character set, mandates the suggestion support part of CJK Unified Ideographs Extension B in GB 18030-2005, along with updates up to Unicode 11.0 including Kangxi Radicals and CJK Unified Ideographs URO, Extension C, D, E and F. Additional languages are also recognized by GB 18030-2022 such as part of Arabic, Tai Le, New Tai Lue, Tai Tham, Lisu, and Miao. GB 18030-2022 also introduces three implementation levels, with the requirement of "all products using this standard should implements Implementation Level 1" that includes 66 new BMP characters in the 4-byte encoding region that were added between Unicode 3.1 and Unicode 11.0. Implementation Level 2 requires the support of List of Commonly Used Standard Chinese Characters, and Implementation Level 3 requires all other specified regions in the standard.

From late 2022 to 2023, drafts of a further amendment are to be made to GB 18030-2022 available for public consultation. The current draft updates up to Unicode 15.1 on Ideographic Description Characters, CJK Unified Ideographs URO, Extension A, B, C, G, H and I. Originally, in late 2022, it would have placed 897 new sinographic characters in Plane 10 (hexadecimal: 0A), a yet-untitled astral Unicode plane, for citizen real-name certification in China, but eventually the repertoire (reduced to 622 characters after expert review) was fast-tracked into Unicode 15.1 in September 2023, as the CJK Unified Ideographs Extension I block. Following this, the amendment draft was modified to use the Extension I code points.

Mapping

GB 18030 defines a one (ASCII), two (extended GBK), or four-byte (UTF) encoding. The two-byte codes are defined in a lookup table, while the four-byte codes are defined sequentially (hence algorithmically) to fill otherwise unencoded parts in UCS. GB 18030 inherits the bad aspects of GBK, most notably needing special code to safely find ASCII characters in a GB18030 sequence.

The one- and two-byte code points are essentially GBK with the euro sign, PUA mappings for unassigned/user-defined points, and vertical punctuations. The four byte scheme can be thought of as consisting of two units, each of two bytes. Each unit has a similar format to a GBK two byte character but with a range of values for the second byte of 0x30–0x39 (the ASCII codes for decimal digits). The first byte has the range 0x81 to 0xFE, as before. This means that a string-search routine that is safe for GBK should also be reasonably safe for GB18030 (in much the same way that a basic byte-oriented search routine is reasonably safe for EUC).

This gives a total of 1,587,600 (126×10×126×10) possible 4-byte sequences, which is easily sufficient to cover Unicode's 1,112,064 (17×65536 − 2048 surrogates) assigned, reserved, and noncharacter code points.

Unfortunately, to further complicate matters there are no simple rules to translate between a 4-byte sequence and its corresponding code point. Instead, codes are allocated sequentially (with the first byte containing the most significant part and the last the least significant part) only to Unicode code points that are not mapped in any other manner. For example:

U+00DE (Þ) → 81 30 89 37
U+00DF (ß) → 81 30 89 38
U+00E0 (à) → A8 A4
U+00E1 (á) → A8 A2
U+00E2 (â) → 81 30 89 39
U+00E3 (ã) → 81 30 8A 30

An offset table is used in the WHATWG and W3C version of GB 18030 to efficiently translate code points. ICU and glibc use similar range definitions to avoid wasting space on large sequential blocks.

Support

This section needs expansion. You can help by adding to it. (October 2016)

Encoding

GB 18030 has been supported on Windows since the release of Windows 95, as code page 54936. Windows 2000 and XP offer a GB18030 Support Package. The open source PostgreSQL database supports GB18030 through its full support for UTF-8, i.e. by converting it to and from UTF-8. Similarly Microsoft SQL Server supports GB18030 by conversion to and from UTF-16.

More specifically, supporting the GB18030 encoding on Windows means that Code Page 54936 is supported by MultiByteToWideChar and WideCharToMultiByte. Due to the backward compatibility of the mapping, many files in GB18030 can be actually opened successfully as the legacy Code Page 936, that is GBK, even if the Code Page 54936 is not supported. However, that is only true if the file in question contains only GBK characters. Loading will fail or cause corrupted result if the file contains characters that do not exist in GBK (see § Technical details for examples).

GNU glibc's gconv, the character codec library used on most Linux distributions, supports GB 18030-2000 since 2.2, and GB 18030-2005 since 2.14; glibc notably includes non-PUA mappings for GB 18030-2005 in order to achieve round-trip conversion. GNU libiconv, an alternative iconv implementation frequently used on non-glibc UNIX-like environments like Cygwin, supports GB 18030 since version 1.4.

As of 2022, "supporting non-Chinese scripts continues to be optional" (presumably for display/font support only; and in China, since the encoding is a full UTF). The standard is known to support English/ASCII and the "following non-Chinese scripts are recognized by GB 18030-2022: Arabic, Tibetan, Mongolian, Tai Le, New Tai Lue, Tai Tham, Yi, Lisu, Hangul (Korean), and Miao."

Fonts

The GB18030 Support Package for Windows contains SimSun18030.ttc, a TrueType font collection file which combines two Chinese fonts, SimSun-18030 and NSimSun-18030. The SimSun 18030 font includes all the characters in Unicode 2.1 plus new characters found in the Unicode CJK Unified Ideographs Extension A block although, despite its name, it does not contain glyphs for all characters encoded by GB 18030, as all (about a million) Unicode code points up to U+10FFFF can be encoded as GB 18030. GB 18030 compliance certification only requires correct handling and recognition of glyphs in the mandatory (two-byte, and CJK Ext. A) Chinese part. Nevertheless, the requirement of PUA characters in the standard have hampered this implementation.

Microsoft YaHei and DengXian provided by Microsoft are updated in 2023 to match GB 18030-2022 implementation level 2, and SimSun is updated to match implementation level 3.

Source Han Sans (and its counterpart Noto Sans CJK) are already compliant with GB 18030-2022 implementation level 2 when the standard update for GB 18030 is announced as of November 2022. Source Han Serif (and its counterpart Noto Serif CJK) however is not compliant at the time, and an update is provided to ensure the font is compliant to implementation level 2. Similarly Microsoft YaHei and PingFang (Apple) require a small number of URO additions that are associated with implementation level 1 in order to become compliant with GB 18030-2022 implementation level 2.

Other CJK font families like HAN NOM and Hanazono Mincho provide wider coverage for Unicode CJK Extension blocks than SimSun-18030 or even SimSun (Founder Extended), but they don't support all code points defined in GB 18030.

See also

• Guobiao code
• CJK characters
• Chinese character encoding
• Comparison of Unicode encodings

Notes

1. Note that GB18030 omits surrogates; see #Mapping.
2. The euro sign is an exception which is given a single byte code of 0x80 in Microsoft's later versions of CP936/GBK and a two byte code of A2 E3 in GB18030.
3. The code points include the 66 Unicode noncharacters.
4. ICU seems to erroneously consider this code point valid, which is in neither versions of the published standards. WHATWG assigns this byte to U+20AC (GBK euro sign) in its universal gb2312-gbk-gb18030 decoder.
5. For a finer division of this range, see GBK (character encoding) § Encoding.
6. Some code points are encoded with two bytes (upper row), the others with four bytes (lower row). U+FFFF is encoded as 84 31 A4 39 on page 239 of the 2005 standard, although the standard gives as far as 84 39 FE 39 for BMP mapping.
7. These are surrogate code points; they have no meaning outside of UTF-16 encoding.
8. Furthermore, due to the encodings of U+E7C7 and U+1E3F having been swapped, U+E7C7 is encoded in the 2005 edition of the standard as 81 35 F4 37, between U+1E3E (81 35 F4 36) and U+1E40 (81 35 F4 38). Hence, only the 2000 edition is entirely sequential in allocating the four-byte codes to otherwise unmapped code points.

References

1. Anthony Fok (2002-03-15). "Application of IANA Charset Registration for GB18030". IANA Character Set Registrations. Retrieved 2016-12-05.
2. "Disruptive Changes in GB 18030-2022" (PDF). www.unicode.org. Retrieved 2024-02-12.
3. "[JDK-8301119] Support for GB18030-2022 - Java Bug System". bugs.openjdk.org. Retrieved 2023-08-14.
4. "JDK 21 Release Notes". jdk.java.net. Retrieved 2023-08-14.
5. "[JDK-8307340] Release Note: Support for GB18030-2022 - Java Bug System". bugs.openjdk.org. Retrieved 2023-08-30.
6. ^ CESI (2009-07-08). "GB18030 符合性问与答" [GB18030 compliance FAQ]. CESI Certification Center. Archived from the original on 2016-09-28. Retrieved 2016-10-12. Page 4 同时达到以下两个要求的产品，为符合GB 18030-2005强制部分的产品：①产品可以正确输入、输出、处理GB 18030-2005强制部分规定的全部汉字字符；②产品可以正确识别GB 18030-2005强制性部分规定的全部汉字字符对应的编码。 Alt URL
7. ^ Standardization Administration of China (SAC) (2005-11-18). GB 18030-2005: Information Technology—Chinese coded character set.
8. "Unicode FAQ on GB 18030". ICU Project. Retrieved 10 September 2016.
9. ^ GB 18030-2000: Information Technology—Chinese ideograms coded character set for information interchange—Extension for the basic set. 2000-03-17. {{cite book}}: |work= ignored (help)
10. ^ Lunde, Ken (2006). "L2/06-394 Update on GB 18030:2005". Unicode Technical Committee Document Registry. Retrieved 28 September 2016.
11. ^ Lunde, Ken (4 August 2022). "The GB 18030-2022 Standard". Medium. Retrieved 7 August 2022.
12. "Group:GBK外字". GlyphWiki. Retrieved 11 September 2016.
13. ^ Lunde, Ken (December 2008). CJKV Information Processing. O'Reilly Media, Inc. ISBN 978-0-596-51447-1. Retrieved 11 September 2016.
14. CESI (2009-07-08). "GB18030 符合性问与答" [GB18030 compliance FAQ]. CESI Certification Center. Archived from the original on 2016-09-28. Retrieved 2016-10-12. Page 4 同时达到以下两个要求的产品，为符合GB 18030-2005强制部分的产品：①产品可以正确输入、输出、处理GB 18030-2005强制部分规定的全部汉字字符；②产品可以正确识别GB 18030-2005强制性部分规定的全部汉字字符对应的编码。
15. Lunde, Dr Ken (2023-11-12). "The First Amendment". Medium. Retrieved 2024-09-09.
16. China National Body (2023-04-26). "GB 18030—2022《信息技术 中文编码字符集》国家标准第１号修改单（征求意见稿）" (PDF). UTC L2/23-113.
17. ^ China National Body (2023-10-13). "IRG #61 Activity Report" (PDF). ISO/IEC JTC1/SC2/WG2/IRG N2623; UTC L2/23-240.
18. United States National Body (May 1, 2023). "USNB Comments on Draft 2 of GB 18030-2022 Amendment 1 and recommendation for ISO/IEC 10646:2020 Amendment 2" (PDF). ISO/IEC JTC1/SC2 N4852, WG2 N5222; UTC L2/23-115.
19. ^ Authoritative mapping table between GB18030-2000 and Unicode. ICU – International Components for Unicode. 2001-02-21. Accessed 2016-09-04.
20. "Encoding Standard # gb18030-index". WHATWG. Retrieved 2016-09-24.
21. Bridge, Karl (13 October 2021). "MultiByteToWideChar function (stringapiset.h) - Win32 apps". learn.microsoft.com. Retrieved 2022-11-01.
22. Microsoft. "GB18030 Support Package". Microsoft. Archived from the original on 2012-06-05.
23. Drepper, Ulrich. "GB18030 iconv module for glibc". glibc git. Retrieved 29 November 2016.
24. Drepper, Ulrich. "Update GB18030 to 2005 version". glibc git. Retrieved 29 November 2016.
25. Weimer, Florian; O'Donell, Carlos. "Status of GB18030 tables (#19575)". Sourceware Bugzilla. Retrieved 29 November 2016.
26. "NEWS - libiconv.git - libiconv". git.savannah.gnu.org. Retrieved 2016-10-13.
27. ^ Lunde, Ken (2022-08-16). "The GB 18030-2022 Standard". Medium. Retrieved 2022-11-01.
28. Lunde, Ken. "If gb18030 is revised, consider aligning the Encoding Standard · Issue #27 · whatwg/encoding". GitHub. Besides, supporting PUA code points in the context of the Noto CJK and Source Han fonts is a total non-starter, mainly because they are Pan-CJK typefaces, and PUA usage is extremely dangerous in such contexts. One of my friends at CESI shared with me the text from the final draft a few days ago. This confirmed that the PUA requirement for the 24 characters is being lifted.
29. "July 11, 2023—KB5028171 (OS Build 20348.1850) - Microsoft Support". support.microsoft.com. Microsoft. Retrieved 25 March 2024.
30. VietUnicode. "/hannom". sourceforge.net. Retrieved 2016-10-13.
31. "Hanazono fonts". fonts.jp. Archived from the original on 2010-04-12. Retrieved 2016-10-13.

External links

• IANA Charset Registration for GB18030
• "English language summary of  – -2000" (PDF). February 16, 2001. Archived from the original (PDF) on 2017-02-02.
• Introduction to GB18030 including evolution from GB2312 and GBK (Sun/Internet Archive)
• ICU data
  • GB18030: A mega-codepage (IBM DeveloperWorks)
  • Authoritative mapping table between GB18030-2000 and Unicode
  • ICU Converter Explorer: GB18030
• Unicode charts
  • Unicode CJK Unified Ideographs Extension A (PDF, 1.5 MB)
  • Unicode CJK Unified Ideographs Extension B (PDF, 13 MB)
• GB18030 Support Package for Windows 2000/XP, including Chinese, Tibetan, Yi, Mongolian and Thai font by Microsoft (Internet Archive)
• SIL's freeware fonts, editors and documentation

v t e Character encodings
Early telecommunications	Telegraph code Needle Morse Non-Latin Wabun/Kana Chinese Cyrillic Baudot and Murray Fieldata ASCII ISO/IEC 646 BCDIC Teletex and Videotex/Teletext T.51/ISO/IEC 6937 ITU T.61 ITU T.101 World System Teletext background sets Transcode
ISO/IEC 8859	Approved parts -1 (Western Europe) -2 (Central Europe) -3 (Maltese/Esperanto) -4 (North Europe) -5 (Cyrillic) -6 (Arabic) -7 (Greek) -8 (Hebrew) -9 (Turkish) -10 (Nordic) -11 (Thai) -13 (Baltic) -14 (Celtic) -15 (New Western Europe) -16 (Romanian) Abandoned parts -12 (Devanagari) Proposed but not approved KOI-8 Cyrillic Sámi Adaptations Welsh Barents Cyrillic Estonian Ukrainian Cyrillic
Bibliographic use	MARC-8 ANSEL CCCII/EACC ISO 5426 5426-2 5427 5428 6438 6862
National standards	ArmSCII Big5 BraSCII CNS 11643 DIN 66003 ELOT 927 GOST 10859 GB 2312 GB 12345 GB 12052 GB 18030 HKSCS ISCII JIS X 0201 JIS X 0208 JIS X 0212 JIS X 0213 KOI-7 KPS 9566 KS X 1001 KS X 1002 LST 1564 LST 1590-4 PASCII Shift JIS SI 960 TIS-620 TSCII VISCII VSCII YUSCII
ISO/IEC 2022	ISO/IEC 8859 ISO/IEC 10367 Extended Unix Code / EUC
Mac OS Code pages ("scripts")	Armenian Arabic Barents Cyrillic Celtic Central European Croatian Cyrillic Devanagari Farsi (Persian) Font X (Kermit) Gaelic Georgian Greek Gujarati Gurmukhi Hebrew Iceland Inuit Keyboard Latin (Kermit) Maltese/Esperanto Ogham Roman Romanian Sámi Turkish Turkic Cyrillic Ukrainian VT100
DOS code pages	437 668 708 720 737 770 773 775 776 777 778 850 851 852 853 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 897 899 903 904 932 936 942 949 950 951 1040 1042 1043 1046 1098 1115 1116 1117 1118 1127 3846 ABICOMP CS Indic CSX Indic CSX+ Indic CWI-2 Iran System Kamenický Mazovia MIK
IBM AIX code pages	895 896 912 915 921 922 1006 1008 1009 1010 1012 1013 1014 1015 1016 1017 1018 1019 1046 1124 1133
Windows code pages	CER-GS 932 936 (GBK) 950 1169 Extended Latin-8 1250 1251 1252 1253 1254 1255 1256 1257 1258 1270 Cyrillic + Finnish Cyrillic + French Cyrillic + German Polytonic Greek
EBCDIC code pages	Japanese language in EBCDIC DKOI
DEC terminals (VTx)	Multinational (MCS) National Replacement (NRCS) French Canadian Swiss Spanish United Kingdom Dutch Finnish French Norwegian and Danish Swedish Norwegian and Danish (alternative) 8-bit Greek 8-bit Turkish SI 960 Hebrew Special Graphics Technical (TCS)
Platform specific	1052 1053 1054 1055 1056 1057 1058 Acorn RISC OS Amstrad CPC Apple II ATASCII Atari ST BICS Casio calculators CDC Compucolor 8001 Compucolor II CP/M+ DEC RADIX 50 DEC MCS/NRCS DG International Galaksija GEM GSM 03.38 HP Roman HP FOCAL HP RPL SQUOZE LICS LMBCS MSX NEC APC NeXT PETSCII PostScript Standard PostScript Latin 1 SAM Coupé Sega SC-3000 Sharp calculators Sharp MZ Sinclair QL Teletext TI calculators TRS-80 Ventura International WISCII XCCS ZX80 ZX81 ZX Spectrum
Unicode / ISO/IEC 10646	UTF-1 UTF-7 UTF-8 UTF-16 UTF-32 UTF-EBCDIC GB 18030 DIN 91379 BOCU-1 CESU-8 SCSU TACE16 Comparison of Unicode encodings
TeX typesetting system	Cork LY1 OML OMS OT1
Miscellaneous code pages	ABICOMP ASMO 449 Digital encoding of APL symbols ISO-IR-68 ARIB STD-B24 Fieldata HZ IEC-P27-1 INIS 7-bit 8-bit ISO-IR-169 ISO 2033 KOI KOI8-R KOI8-RU KOI8-U Mojikyō SEASCII Stanford/ITS Symbol TRON Unified Hangul Code
Control character	Morse prosigns C0 and C1 control codes ISO/IEC 6429 JIS X 0211 Unicode control, format and separator characters Whitespace characters
Related topics	CCSID Character encodings in HTML Charset detection Han unification Hardware code page MICR code Mojibake Variable-length encoding
Character sets

• Guobiao standards
• Unicode Transformation Formats
• Chinese character encodings