[Unicode]   Technical Reports


Working Draft for Proposed Update

Unicode Standard Annex #44

Unicode Character Database

Version Unicode 5.2 draft 1
Authors Mark Davis (markdavis@google.com) and Ken Whistler (ken@unicode.org)
Date 2008-7-03
This Version http://www.unicode.org/reports/tr44/tr44-3.html
Previous Version http://www.unicode.org/reports/tr44/tr44-2.html
Latest Version http://www.unicode.org/reports/tr44/
Revision 3


This annex consolidates information documenting the Unicode Character Database.


This is a draft document which may be updated, replaced, or superseded by other documents at any time. Publication does not imply endorsement by the Unicode Consortium. This is not a stable document; it is inappropriate to cite this document as other than a work in progress.

A Unicode Standard Annex (UAX) forms an integral part of the Unicode Standard, but is published online as a separate document. The Unicode Standard may require conformance to normative content in a Unicode Standard Annex, if so specified in the Conformance chapter of that version of the Unicode Standard. The version number of a UAX document corresponds to the version of the Unicode Standard of which it forms a part.

Please submit corrigenda and other comments with the online reporting form [Feedback]. Related information that is useful in understanding this annex is found in Unicode Standard Annex #41, “Common References for Unicode Standard Annexes.” For the latest version of the Unicode Standard, see [Unicode]. For a list of current Unicode Technical Reports, see [Reports]. For more information about versions of the Unicode Standard, see [Versions]. For any errata which may apply to this annex, see [Errata].



Warning: the information in this annex does not completely describe the use and interpretation of Unicode character properties and behavior. It must be used in conjunction with the data in the other files in the Unicode Character Database, and relies on the notation and definitions supplied in The Unicode Standard. All chapter references are to Version 5.0.0 of the standard unless otherwise indicated.

1 Introduction

The Unicode Standard is far more than a simple encoding of characters. The standard also associates a rich set of semantics with each encoded character—properties that are required for interoperability and correct behavior in implementations, as well as for Unicode conformance. These semantics are embodied in the Unicode Character Database (UCD), a collection of data files which contain the Unicode character code points and character names. The data files define the Unicode character properties and mappings between Unicode characters (such as case mappings).

This annex describes the UCD and provides a guide to the various documentation files associated with it.

The latest version of the UCD is always located on the Unicode Web site at:


The specific files for the UCD associated with this version of the Unicode Standard (5.2.0) are located at:


Stable, archived versions of the UCD associated with all earlier versions of the Unicode Standard can be accessed from:


For a description of the changes in the UCD for this version and earlier versions, see UCD Change History.

2 Conformance

The Unicode Character Database is an integral part of the Unicode Standard.

The UCD contains normative property and mapping information required for implementation of various Unicode algorithms such as the Unicode Bidirectional Algorithm, Unicode Normalization, and Unicode Casefolding. The data files also contain additional informative and provisional character property information.

Each specification of a Unicode algorithm, whether specified in the text of [Unicode] or in one of the Unicode Standard Annexes, designates which data file(s) in the UCD are needed to provide normative property information required by that algorithm.

For information on the meaning and application of the terms, normative, informative, and provisional, see Section 3.5, "Properties" in [Unicode].

For information about the applicable terms of use for the UCD, see the Unicode Terms of Use.

2.1 Simple and Derived Properties

Some character properties in the UCD are simple properties. This status has no bearing on whether or not the properties are normative, but merely indicates that their values are not derived from some combination of other properties.

Other character properties are derived. This means that their values are derived by rule from some other combination of properties. Generally such rules are stated as set operations, and may or may not include explicit exception lists for individual characters.

Sometimes simple properties are defined merely to make the statement of the rule defining a derived property more compact or general. Such properties are known as contributory properties. Sometimes these contributory properties are defined to encapsulate the messiness inherent in exception lists. At other times, a contributory property may be defined to help stabilize the definition of an important derived property which is subject to stability guarantees.

Derived character properties are not considered second-class citizens among Unicode character properties. They are defined to make implementation of important algorithms easier to state. Included among the first-class derived properties important for such implementations are: Uppercase, Lowercase, XID_Start, XID_Continue, Math, and Default_Ignorable_Code_Point, all defined in DerivedCoreProperties.txt, and derived properties for the optimization of normalization, defined in DerivedNormalizationProps.txt.

Implementations should simply use the derived properties, and should not try to rederive them from lists of simple properties and collections of rules, because of the chances for error and divergence when doing so.

If there are any cases of mismatches between the definition of a derived property as listed in DerivedCoreProperties.txt or similar data files in the UCD, and the definition of a derived property as a set definition rule, the explicit listing in the data file should always be taken as the normative definition of the property.

Definitions of property derivations are provided for information only, typically in comment fields in the data files. Such definitions may be refactored, refined, or corrected over time. To ensure that there is never any ambiguity between versions of the standard, even if the definition of a derivation is changed at some point in time, the exact property listing in the data files for any given version of the standard is always the truth for that property value for that version—and will never change for that version.

2.2 Use of Default Values

Unicode character properties have default values. Default values are the value or values that a character property takes for an unassigned code point, or in some instances, for designated subranges of code points, whether assigned or unassigned. For example, the default value of a binary Unicode character property is always "N".

For the formal discussion of default values, see D26 in Section 3.5, "Properties" in [Unicode]. For conventions related to default values in various data files of the UCD, see File Format Conventions. For documentation regarding the particular default values of individual Unicode character properties, see the Property Table.

2.3 Stability of Releases

Just as for the Unicode Standard as a whole, each version of the UCD, once published, is absolutely stable and will never change. Each released version is archived in a directory on the Unicode web site, with a directory number associated with that version. URLs pointing to that version's directory are also stable and will be maintained in perpetuity.

Any errors discovered for a released version of the UCD are noted in [Errata], and if appropriate will be corrected in a subsequent version of the UCD.

Stability guarantees constraining how Unicode character properties can (or cannot) change between releases of the UCD are documented in the Unicode Consortium Stability Policies [Stability].

3 Documentation

This annex provides the core documentation for the UCD, but additional information about character properties is available in other parts of the standard and in additional documentation files contained within the UCD itself.

3.1 Character Properties in the Standard

The formal definitions related to character properties used by the Unicode Standard are documented in Section 3.5, "Properties" in [Unicode]. Understanding those definitions and related terminology is essential to the appropriate use of Unicode character properties.

See Section 4.1, "Unicode Character Database", in [Unicode] for a general discussion of the UCD and its use in defining properties. The rest of Chapter 4 provides important explanations regarding the meaning and use of various normative character properties.

3.2 The Character Property Model

For a general discussion of the property model which underlies the definitions associated with the UCD, see UTR #23: The Unicode Character Property Model [UTR23]. That technical report is informative, but over the years various content from it has been incorporated into normative portions of the Unicode Standard, particularly for the definitions in Chapter 3.

UTR #23 also discusses string functions and their relation to character properties.

3.3 NamesList.html

NamesList.html formally describes (in BNF) the format of the NamesList.txt data file, the file which is used to drive the printing of the Unicode code charts and names list. See also Section 17.1, "Character Names List", in [Unicode] for a detailed discussion of the conventions used in the Unicode names list.

3.4 StandardizedVariants.html

StandardizedVariants.html documents standardized variants, showing a representative glyph for each. It is closely tied to the data file, StandardizedVariants.txt, which defines those sequences normatively.

3.5 Unihan and UAX #38

UAX #38, Unicode Han Database (Unihan) [UAX38] describes the format and content of Unihan.txt, the data file which collects together all property information for CJK Unified Ideographs. That annex also specifies in detail which of the Unihan character properties are normative, informative, or provisional.

It is important to note that Unihan.txt and its associated documentation is aimed only at CJK Unified Ideographs. It does not have as its scope legacy East Asian character sets as a whole, which also contain many non-CJK characters. As a result, while Unihan.txt contains extensive and detailed mapping information for CJK Unified Ideographs, it must be supplemented from other sources to establish mapping tables for various important commercial and national character set standards from East Asia.

3.6 Data File Comments

In addition to the specific documentation files for the UCD, individual data files often contain extensive header comments describing their content and any special conventions used in the data.

In some instances, individual property definition sections also contain comments with information about how the property may be derived. Such comments are informative; while they are intended to convey the intent of the derivation, in case of any mismatch between a statement of a derivation in a comment field and the actual listing of the derived property, it is the list which is to be taken as normative. See Simple and Derived Properties.

3.7 Obsolete Documentation Files

UCD.html was formerly the primary documentation file for the UCD. Its content has been wholly incorporated into this document, as of Version 5.2.0.

Unihan.html was formerly the primary documentation file for Unihan.txt. Its content has been wholly incorporated into [UAX38], as of Version 5.1.0.

Much earlier versions of the Unicode Standard contained small, segmented documentation files, UnicodeCharacterDatabase.html, PropList.html, and DerivedProperties.html, which were later incorporated into UCD.html.

4 UCD Files

The heart of the UCD consists of the data files themselves. This section describes the directory structure for the UCD, the format conventions for the data files, and provides documentation for data files not documented elsewhere in this annex.

4.1 Directory Structure

Each version of the UCD is released in a separate, numbered directory under the Public directory on the Unicode web site. The content of that directory is complete for that release. It is also stable—once released, it will be archived permanently in that directory, unchanged, at a stable URL.

The specific files for the UCD associated with this version of the Unicode Standard (5.2.0) are located at:


4.1.1 UCD Files Proper

The UCD proper is located in the ucd subdirectory of the numbered version directory. That directory contains all of the documentation files and most of the data files for the UCD, including some data files for derived properties.

Although all UCD data files are version-specific for a release and most contain internal date and version stamps, the file names of the released data files do not differ from version to version. When linking to a version-specific data file, the version will be indicated by the version number of the directory for the release.

All files for derived extracted properties are in the extracted subdirectory of the ucd subdirectory. See Derived Extracted Properties for documentation regarding those data files and their content.

A number of auxiliary properties are specified in files in the auxiliary subdirectory of the ucd subdirectory. In Version 5.2.0 it contains data files specifying properties associated with UAX #29, Unicode Text Segmentation [UAX29] and with UAX #14, Unicode Line Breaking Algorithm [UAX14], as well as test data for those algorithms. See Segmentation Test Files and Documentation for more information about the test data.

4.1.2 UCD XML Files

The XML version of the UCD is located in the ucdxml subdirectory of the numbered version directory. See the UCD in XML for more details.

4.1.3 Charts

The code charts specific to a version of Unicode are archived as a single large pdf file in the charts subdirectory of the numbered version directory. See the readme.txt in that subdirectory and the general web page explaining the Unicode Code Charts for more details.

4.1.4 Beta Review Considerations

Prior to the formal release for any particular version of the UCD, a beta review is conducted. The beta review files are located in the same directory that is later used for the released UCD, but during the beta review period, the subdirectory structure differs somewhat and may contain temporary files, including documentation of diffs between deltas for the beta review. Also, during the beta review, all data file names are suffixed with version numbers and delta numbers. So a typical file name during beta review may be "PropList-5.2.0d13.txt" instead of the finally released "PropList.txt".

Notices contained in a ReadMe.txt file in the UCD directory during the beta review period also make it clear that that directory contains preliminary material under review, rather than a final, stable release.

4.1.5 File Directory Differences for Early Releases

The UCD in XML was introduced in Version 5.1.0, so UCD directories prior to that do not contain the ucdxml subdirectory.

UCD directories prior to Version 4.1.0 do not contain the auxiliary subdirectory.

UCD directories prior to Version 3.2.0 do not contain the extracted subdirectory.

The general structure of the file directory for a released version of the UCD described above applies to Versions 4.1.0 and later. Prior to Version 4.1.0, versions of the UCD were not self-contained, complete sets of data files for that version, but instead only contained any new data files or any data files which had changed since the prior release.

The directory naming conventions and the file naming conventions also differed prior to Version 4.1.0. So, for example, Version 4.0.0 of the UCD is contained in a directory named 4.0-Update, and Version 4.0.1 of the UCD in a directory named 4.0-Update1. Furthermore, for these earlier versions, the data file names do contain explicit version numbers.

It is important to understand and keep these differences in mind when accessing any version of the UCD earlier than Version 4.1.0. Full details on the exact collection of data files associated with the release of any version of the UCD prior to Version 4.1.0 can be found online by referring to the component listings at Enumerated Versions.

4.2 File Format Conventions

Files in the UCD use the format conventions described in this section, unless otherwise specified.

4.2.1 Data Fields

4.2.2 Code Points and Sequences

4.2.3 Code Point Ranges


4.2.5 Code Point Labels

Code Point Label Tags
Tag General_Category Note
reserved Cn Noncharacter_Code_Point=F
noncharacter Cn Noncharacter_Code_Point=T
control Cc  
private-use Co  
surrogate Cs  


4.2.6 Multiple Values

4.2.7 Binary Property Values

4.2.8 Default Values

Some default values for common catalog, enumeration, and numeric properties are listed in the table below:

Default Values for Properties
Property Name Default Value
Age unassigned
Block No_Block
Canonical_Combining_Class Not_Reordered (= 0)
Decomposition_Type None
East_Asian_Width Neutral
Numeric_Value NaN
Script Unknown (= Zzzz)

Default values for some Unicode character properties such as Bidi_Class are complex. See the relevant annexes and other documentation for more details.

4.2.9 Text Encoding

4.2.10 Other Conventions

4.2.11 Other File Formats

4.3 File List

The exact list of files associated with any particular version of the UCD is available on the web site by referring to the component listings at Enumerated Versions.

The majority of the data files in the UCD provide specifications of character properties for Unicode characters. Those files and their contents are documented in detail in the Property Table section below.

The data files in the extracted subdirectory constitute reformatted listings of single character properties extracted from UnicodeData.txt or other primary data files. The reformatting is provided to make it easier to see the particular set of characters having certain values for enumerated properties, or to separate the statement of that property from other properties defined together in UnicodeData.txt. These extracted, derived data files are further documented in the Derived Extracted Properties section below.

The UCD also contains a number of test data files, whose purpose is to provide standard test cases useful in verifying the implementation of complex Unicode algorithms. See the Test Files section below for more documentation.

The remaining files in the Unicode Character Database do not directly specify Unicode properties. The important ones and their functions are listed in the table below. The Status column indicates whether the file (and its content) is considered Normative, Informative, or Provisional.

Other Files in the UCD
File Name Reference Status Description
Index.txt Chapter 17 I Index to Unicode characters, as printed in the Unicode Standard.
NamesList.txt Chapter 17 I Names list used for production of the code charts, derived from UnicodeData.txt. It contains additional annotations.
NamesList.html Chapter 17 I Documents the format of NamesList.txt.
StandardizedVariants.txt Chapter 16 N Lists all the standardized variant sequences that have been defined, plus a textual description of their desired appearance.
StandardizedVariants.html Chapter 16 N A derived documentation file, generated from StandardizedVariants.txt, plus a list of sample glyphs showing the desired appearance of each standardized variant.
NamedSequences.txt [UAX34] N Lists the names for all approved named sequences.
NamedSequencesProv.txt [UAX34] P Lists the names for all provisional named sequences.

For more information about these files and their use, see the referenced annexes or chapters of Unicode Standard.

4.4 Zipped Files

Starting with Version 4.1.0, zipped versions of all of the UCD files, both data files and documentation files, are available under the Public/zipped directory on the Unicode web site. Each collection of zipped files is located there in a numbered subdirectory corresponding to that version of the UCD.

Two different zipped files are provided for each version:

This bifurcation allows for better management of downloading version-specific information, because Unihan.zip contains all the pertinent CJK-related property information, while UCD.zip contains all of the rest of the UCD property information, for those who may not need the voluminous CJK data.

In versions of the UCD prior to Version 4.1.0, zipped copies of Unihan.txt are provided in the same directory as the UCD data files. These zipped files are only posted for versions of the UCD in which Unihan.txt itself was updated.

4.5 UCD in XML

Starting with Version 5.1.0, a set of XML data files using that schema are also released with each version of the UCD. Those data files make it possible to import and process the UCD property data using standard XML parsing tools, instead of the specialized parsing required for the various individual data files of the UCD.

4.5.1 UAX #42

UAX #42, Unicode Character Database in XML [UAX42] defines an XML schema which is used to incorporate all of the Unicode character property information into the XML version of the UCD. See that annex for details of the schema and conventions regarding the grouping of property values for more compact representations.

4.5.2 XML File List

The XML version of the UCD is contained in the ucdxml subdirectory of the UCD. The files are all zipped. The list of files is shown in the table below:

XML File List
File Name CJK non-CJK
ucd.all.flat.zip x x
ucd.all.grouped.zip x x
ucd.nounihan.flat.zip   x
ucd.nounihan.grouped.zip   x
ucd.unihan.flat.zip x  
ucd.unihan.grouped.zip x  

The "flat" file versions simply list all attributes with no particular compression. The "grouped" file versions apply the grouping mechanism described in [UAX42] to cut down on the size of the data files.

5 Properties

This section documents the Unicode character properties, relating them in detail to the particular UCD data files in which they are specified. For enumerated properties in particular, this section also documents the actual values which those properties can have.

An index of all the non-CJK character properties by name can be found below in the Property Summary section. For a comparable index of CJK character propertes, see UAX #38, Unicode Han Database (Unihan) [UAX38].

5.1 Property Table

The big property table below specifies the list of character properties defined in each data file of the UCD.

For each data file in the UCD there is a separate section of the property table. In that section, the first column lists the character properties specified in that file.

The data files which define a single property or a small number of properties are listed first, followed by the data files which define a large number of properties: DerivedCoreProperties.txt, DerivedNormalizationProps.txt, PropList.txt, and UnicodeData.txt.

For UnicodeData.txt the default property values are listed in the first column in parentheses after the property name, with the special convention (<code point>) indicating that code point itself is the default value.

The second column in the property table indicates the type of the property, according to the following key:

Property Type Key
Property Type Symbol Examples
Catalog C Age, Block
Enumeration E Joining_Type, Line_Break
Binary B Uppercase, White_Space
String S Uppercase_Mapping, Case_Folding
Numeric N Numeric_Value
Miscellaneous M Name, Jamo_Short_Name

The third column in the property table indicates the status of the property: Normative or Informative.

Finally, the fourth column in the property table provides a description of the property or properties. This includes information on derivation for derived properties, as well as references to locations in the standard where the property is defined or discussed in detail.

In the section of the table for UnicodeData.txt, the data field numbers are also supplied in parentheses at the start of the description.

For a few entries in the property table, values specified in the fields in a data file only contribute to a full definition of a Unicode character property. For example, the values in field 1 (Name) in UnicodeData.txt do not provide all the values for the Name property for all code points; Jamo.txt must also be used, and the Name property for CJK Unified Ideographs is derived by rule.

Properties marked as stabilized are no longer actively maintained, nor are they extended as new characters are added.

None of the Unicode character properties should be used simply on the basis of the descriptions in the Property Table without consulting the relevant discussions in the Unicode Standard. Because of the enormous variety of characters in the repertoire of the Unicode Standard, character properties tend not to be self-evident in application, even when the names of the properties may seem familiar from their usage with much smaller legacy character encodings.

Humongous Property Table
E N Basic Arabic and Syriac character shaping properties, such as initial, medial and final shapes. See Section 8.2 in [Unicode].
Bidi_Mirroring_Glyph S I Informative mapping for substituting characters in an implementation of bidirectional mirroring. This maps a subset of characters with the Bidi_Mirrored property to other characters that normally are displayed with the corresponding mirrored glyph. See UAX #9: The Unicode Bidirectional Algorithm [UAX9]. Do not confuse this with the Bidi_Mirrored property itself.
Block C N List of block names, which are arbitrary names for ranges of code points. See Chapter 17 in [Unicode].
Composition_Exclusion B N Properties for normalization. See UAX #15: Unicode Normalization Forms [Norm]. Unlike other files, CompositionExclusions simply lists the relevant code points.
S N Mapping from characters to their case-folded forms. This is an informative file containing normative derived properties.

Derived from UnicodeData and SpecialCasing.

Note: The case foldings are omitted in the data file if they are the same as the code point itself.

Age C N/I This file shows when various code points were designated/assigned in successive versions of the Unicode standard.

The Age property is normative in the sense that it is completely specified based on when a character is encoded in the standard. However, DerivedAge.txt is provided for information. The value of the Age property for a code point can be derived by analysis of successive versions of the UCD, and Age is not used normatively in the specification of any Unicode algorithm.

East_Asian_Width E I Properties for determining the choice of wide versus narrow glyphs in East Asian contexts. Property values are described in UAX #11: East Asian Width [Width].
E N The values L, V, T, LV, and LVT used in Chapter 3 in [Unicode].
M N The Hangul Syllable names are derived from the Jamo Short Names, as described in Chapter 3 in [Unicode].
Line_Break E N Properties for line breaking. For more information, see UAX #14: Unicode Line Breaking Algorithm [UAX14].
Grapheme_Cluster_Break E I

See UAX #29: Unicode Text Segmentation [UAX29]

Sentence_Break E I

See UAX #29: Unicode Text Segmentation [UAX29]

Word_Break E I

See UAX #29: Unicode Text Segmentation [UAX29]

M N Normative formal aliases for characters with erroneous names, as described in Chapter 4 in [Unicode]. These aliases exactly match the formal aliases published in the Unicode Standard code charts.
used in Decomposition Mappings S N NormalizationCorrections lists code point differences for Normalization Corrigenda. For more information, see UAX #15: Unicode Normalization Forms [UAX15].
Script C I Script values for use in regular expressions. For more information, see UAX #24: Unicode Script Property [UAX24].
S I Data for producing (in combination with the simple case mappings from UnicodeData.txt) the full case mappings.
Unihan.txt (for more information, see [UAX38])
E I The characters tagged with kPrimaryNumeric, kAccountingNumeric, and kOtherNumeric are given the Numeric_Type numeric, and the values indicated.

Most characters have these properties based on values from UnicodeData.txt. See Numeric_Type.

Unicode_Radical_Stroke M I The Unicode radical-stroke count, based on the tag kRSUnicode.
Alphabetic B I Characters with the Alphabetic property. For more information, see Chapter 4 in [Unicode].

Generated from: Lu + Ll + Lt + Lm + Lo + Nl + Other_Alphabetic

Default_Ignorable_Code_Point B N For programmatic determination of default ignorable code points. New characters that should be ignored in rendering (unless explicitly supported) will be assigned in these ranges, permitting programs to correctly handle the default rendering of such characters when not otherwise supported. For more information, see the FAQ Display of Unsupported Characters, and Section 5.20, "Default Ignorable Code Points" in [Unicode].

Generated from
+ Cf (format characters)
+ Variation_Selector
- White_Space
- FFF9..FFFB (annotation characters)
- 0600..0603, 06DD, 070F (exceptional Cf characters that should be visible)

Lowercase B I Characters with the Lowercase property. For more information, see Chapter 4 in [Unicode].

Generated from: Ll + Other_Lowercase

Grapheme_Base B I For programmatic determination of grapheme cluster boundaries. For more information, see UAX #29: Unicode Text Segmentation [UAX29].

Generated from: [0..10FFFF] - Cc - Cf - Cs - Co - Cn - Zl - Zp - Grapheme_Extend

Grapheme_Extend B I For programmatic determination of grapheme cluster boundaries. For more information, see UAX #29: Unicode Text Segmentation [UAX29].

Generated from: Me + Mn + Other_Grapheme_Extend

Note: Depending on an application's interpretation of Co (private use), they may be either in Grapheme_Base, or in Grapheme_Extend, or in neither.

Grapheme_Link B I Deprecated property, formerly proposed for programmatic determination of grapheme cluster boundaries.

Generated from: Canonical_Combining_Class=Virama

ID_Start B I Used to determine programming identifiers, as described in UAX #31: Unicode Identifier and Pattern Syntax [UAX31].
ID_Continue B I
Math B I Characters with the Math property. For more information, see Chapter 4 in [Unicode].

Generated from: Sm + Other_Math

Uppercase B I Characters with the Uppercase property. For more information, see Chapter 4 in [Unicode].

Generated from: Lu + Other_Uppercase

XID_Start B I Used to determine programming identifiers, as described in UAX #31: Unicode Identifier and Pattern Syntax [UAX31].
XID_Continue B I
Full_Composition_Exclusion B N Characters that are excluded from composition: those listed explicitly in CompositionExclusions.txt, plus the derivable sets of Singleton Decompositions and Non-Starter Decompositions, as documented in that data file.
B N Characters that expand to more than one character in the specified normalization form.
FC_NFKC_Closure S N Characters that require extra mappings for closure under Case Folding plus Normalization Form KC. Characters marked with this property have a third field with the mapping in it.

Generated with the following, where Fold is defined as the default fold operation (excluding the Turkic-specific foldings):

b = NFKC(Fold(a));
c = NFKC(Fold(b));
if (c != b) add mapping from a to c
to the set of mappings that constitute the FC_NFKC_Closure list

Note: The FC_NFKC_Closure value is omitted in the data file if it is the same as the code point itself.

E N For property values, see Decompositions and Normalization. (Abbreviated names: NFD_QC, NFKD_QC, NFC_QC, NFKC_QC)
ASCII_Hex_Digit B N ASCII characters commonly used for the representation of hexadecimal numbers.
Bidi_Control B N Format control characters which have specific functions in the Unicode Bidirectional Algorithm [UAX9].
Dash B I Punctuation characters explicitly called out as dashes in the Unicode Standard, plus their compatibility equivalents. Most of these have the General_Category value Pd, but some have the General_Category value Sm because of their use in mathematics.
Deprecated B N For a machine-readable list of deprecated characters. No characters will ever be removed from the standard, but the usage of deprecated characters is strongly discouraged.
Diacritic B I Characters that linguistically modify the meaning of another character to which they apply. Some diacritics are not combining characters, and some combining characters are not diacritics.
Extender B I Characters whose principal function is to extend the value or shape of a preceding alphabetic character. Typical of these are length and iteration marks.
Hex_Digit B I Characters commonly used for the representation of hexadecimal numbers, plus their compatibility equivalents.
Hyphen (Stabilized as of 3.2) B I Dashes which are used to mark connections between pieces of words, plus the Katakana middle dot. The Katakana middle dot functions like a hyphen, but is shaped like a dot rather than a dash.
Ideographic B I Characters considered to be CJKV (Chinese, Japanese, Korean, and Vietnamese) ideographs.
IDS_Binary_Operator B N Used in Ideographic Description Sequences.
IDS_Trinary_Operator B N Used in Ideographic Description Sequences.
Join_Control B N Format control characters which have specific functions for control of cursive joining and ligation.
Logical_Order_Exception B N There are a small number of characters that do not use logical order. These characters require special handling in most processing.
Noncharacter_Code_Point B N Code points permanently reserved for internal use.
Other_Alphabetic B I Used in deriving the Alphabetic property.
Other_Default_Ignorable_Code_Point B N Used in deriving the Default_Ignorable_Code_Point property.
Other_Grapheme_Extend B N Used in deriving  the Grapheme_Extend property.
Other_ID_Continue B N Used for backward compatibility of ID_Continue.
Other_ID_Start B N Used for backward compatibility of ID_Start.
Other_Lowercase B I Used in deriving the Lowercase property.
Other_Math B I Used in deriving the Math property.
Other_Uppercase B I Used in deriving the Uppercase property.
Pattern_Syntax B N Used for pattern syntax as described in UAX #31: Unicode Identifier and Pattern Syntax [Pattern].
Pattern_White_Space B N
Quotation_Mark B I Punctuation characters that function as quotation marks.
Radical B N Used in Ideographic Description Sequences.
Soft_Dotted B N Characters with a "soft dot", like i or j. An accent placed on these characters causes the dot to disappear. An explicit dot above can be added where required, such as in Lithuanian.
STerm B I Sentence Terminal. Used in UAX #29: Unicode Text Segmentation [UAX29].
Terminal_Punctuation B I Punctuation characters that generally mark the end of textual units.
Unified_Ideograph B N Used in Ideographic Description Sequences.
Variation_Selector B N Indicates characters that are Variation Selectors. For details on the behavior of these characters, see StandardizedVariants.html, Section 16.4, Variation Selectors in [Unicode], and the Unicode Ideographic Variation Database [UTS37].
White_Space B N Separator characters and control characters which should be treated by programming languages as "white space" for the purpose of parsing elements.

Note: ZERO WIDTH SPACE and ZERO WIDTH NO-BREAK SPACE are not included, because their functions are restricted to line-break control. Their names are unfortunately misleading in this respect.

Note: There are other senses of "whitespace" that encompass a different set of characters.

Name (<none>) M N (1) These names match exactly the names published in the code charts of the Unicode Standard. The derived Hangul Syllable names are omitted from this file; see Jamo.txt for their derivation.
General_Category (Cn) E N (2) This is a useful breakdown into various character types which can be used as a default categorization in implementations. For the property values, see General Category Values.
Canonical_Combining_Class (0) N N (3) The classes used for the Canonical Ordering Algorithm in the Unicode Standard. This property could be considered either an enumerated property or a numeric property: the principal use of the property is in terms of the numeric values. For the property value names associated with different numeric values, see DerivedCombiningClass.txt and Canonical Combining Class Values.
Bidi_Class (L, AL, R) E N (4) These are the categories required by the Unicode Bidirectional Algorithm. For the property values, see Bidirectional Class Values. For more information, see UAX #9: The Unicode Bidirectional Algorithm [UAX9].

The default property values depend on the code point, and are given in DerivedBidiClass.txt

Decomposition_Type (None)
Decomposition_Mapping (<code point>)
N (5) This field contains both values, with the type in angle brackets. The decomposition mappings exactly match the decomposition mappings published with the character names in the Unicode Standard. For more information, see Character Decomposition Mappings.

Note: The decomposition mapping is omitted in the data file if the decomposition mapping is the same as the code point itself.

Numeric_Type (None)
Numeric_Value (NaN)
N (6) If the character has the decimal digit property, as specified in Chapter 4 in [Unicode], then the value of that digit is represented with an integer value in fields 6, 7, and 8.
N (7) If the character has the digit property, but is not a decimal digit, then the value of that digit is represented with an integer value in fields 7 and 8. This covers digits that need special handling, such as the compatibility superscript digits.
N (8) If the character has the numeric property, as specified in Chapter 4 in [Unicode], the value of that character is represented with a positive or negative integer or rational number in this field. This includes fractions such as, for example, "1/5" for U+2155 VULGAR FRACTION ONE FIFTH.

Some characters have these properties based on values from the Unihan data file. See Numeric_Type, Han.

Bidi_Mirrored (N) B N (9) If the character is a "mirrored" character in bidirectional text, this field has the value "Y"; otherwise "N". See Section 4.7, "Bidi Mirrored—Normative" of [Unicode]. Do not confuse this with the Bidi_Mirroring_Glyph property.
Unicode_1_Name (<none>) M I (10) Old name as published in Unicode 1.0. This name is only provided when it is significantly different from the current name for the character. The value of field 10 for control characters does not always match the Unicode 1.0 names. Instead, field 10 contains ISO 6429 names for control functions, for printing in the code charts.
ISO_Comment (<none>) M I (11) ISO 10646 comment field. It appears in parentheses in the 10646 names list, or contains an asterisk to mark an Annex P note.
(<code point>)
S N (12) Simple uppercase mapping (single character result).
If a character is part of an alphabet with case distinctions, and has a simple uppercase equivalent, then the uppercase equivalent is in this field. The simple mappings have a single character result, where the full mappings may have multi-character results. For more information, see Case and Case Mapping.

Note: The simple uppercase is omitted in the data file if the uppercase is the same as the code point itself.

(<code point>)
S N (13) Simple lowercase mapping (single character result).

Note: The simple lowercase is omitted in the data file if the lowercase is the same as the code point itself.

(<code point>)
S N (14) Simple titlecase mapping (single character result).

Note: The simple titlecase may be omitted in the data file if the titlecase is the same as the uppercase.


5.2 Derived Extracted Properties

A number of Unicode character properties have been separated out, reformatted, and listed in range format, one property per file. These files are located under the extracted directory of the UCD. The exact list of derived extracted files and the extracted properties they represent are given in the Extracted Properties table below.

The derived extracted files are provided purely as a reformatting of data for properties specified in other data files. In case of any inadvertant mismatch between the primary data files specifying those properties and these lists of extracted properties, the primary data files are taken as definitive.

Extracted Properties
File Status Property Extracted from
DerivedBidiClass.txt N Bidi_Class UnicodeData.txt, field 4
DerivedBinaryProperties.txt N Bidi_Mirrored UnicodeData.txt, field 9
DerivedCombiningClass.txt N Canonical_Combining_Class UnicodeData.txt, field 3
DerivedDecompositionType.txt N/I Decomposition_Type the <tag> in UnicodeData.txt, field 5
DerivedEastAsianWidth.txt I East_Asian_Width EastAsianWidth.txt, field 1
DerivedGeneralCategory.txt N General_Category UnicodeData.txt, field 2
DerivedJoiningGroup.txt N Joining_Group ArabicShaping.txt, field 2
DerivedJoiningType.txt N Joining_Type ArabicShaping.txt, field 1
DerivedLineBreak.txt N Line_Break LineBreak.txt, field 1
DerivedNumericType.txt N Numeric_Type UnicodeData.txt, fields 6 through 8
DerivedNumericValues.txt N Numeric_Value UnicodeData.txt, field 8

For the extraction of Decomposition_Type, characters with canonical decomposition mappings in field 5 of UnicodeData.txt have no tag. For those characters, the extracted value is Decomposition_Type=Canonical. For characters with compatibility decomposition mappings, there are explicit tags in field 5, and the value of Decomposition_Type is equivalent to those tags. The value Decomposition_Type=Canonical is normative. Other values for Decomposition_Type are informative.

Numeric_Value is extracted based on the actual numeric value of the data in field 8 of UnicodeData.txt.

Numeric_Type is extracted as follows. If fields 6, 7, and 8 in UnicodeData.txt are all non-empty, then Numeric_Type=Decimal. Otherwise, if fields 7 and 8 are both non-empty, then Numeric_Type=Digit. Otherwise, if field 8 is non-empty, then Numeric_Type=Numeric. The default value is Numeric_Type=None.

5.3 Property Summary

The following table provides a summary list of the Unicode character properties, excluding most of those specific to Unihan.txt. The properties are roughly organized into groups based on their usage. This grouping is primarily for documentation convenience and except for contributory properties, has no normative implications. The link on each property leads its description in the Property Table above.

Property Summary Table
General Decomposition and Normalization CJK
Name Canonical_Combining_Class Ideographic
Name_Alias Decomposition_Mapping Unified_Ideograph
Block Composition_Exclusion Radical
Age Full_Composition_Exclusion IDS_Binary_Operator
General_Category Decomposition_Type IDS_Trinary_Operator
Script FC_NFKC_Closure Unicode_Radical_Stroke
White_Space NFC_Quick_Check Miscellaneous
Alphabetic NFKC_Quick_Check Math
Hangul_Syllable_Type NFD_Quick_Check Quotation_Mark
Noncharacter_Code_Point NFKD_Quick_Check Dash
Default_Ignorable_Code_Point Expands_On_NFC Hyphen
Deprecated Expands_On_NFD STerm
Logical_Order_Exception Expands_On_NFKC Terminal_Punctuation
Variation_Selector Expands_On_NFKD Diacritic
Case Shaping and Rendering Extender
Uppercase Join_Control Grapheme_Base
Lowercase Joining_Group Grapheme_Extend
Lowercase_Mapping Joining_Type Grapheme_Link (deprecated)
Titlecase_Mapping Line_Break Unicode_1_Name
Uppercase_Mapping Grapheme_Cluster_Break ISO_Comment
Case_Folding Sentence_Break Contributory Properties
Simple_Lowercase_Mapping Word_Break Other_Alphabetic
Simple_Titlecase_Mapping East_Asian_Width Other_Default_Ignorable_Code_Point
Simple_Uppercase_Mapping Bidirectional Other_Grapheme_Extend
Simple_Case_Folding Bidi_Class Other_ID_Start
Soft_Dotted Bidi_Control Other_ID_Continue
Identifiers Bidi_Mirrored Other_Lowercase
ID_Continue Bidi_Mirroring_Glyph Other_Math
ID_Start Numeric Other_Uppercase
XID_Continue Numeric_Value Jamo_Short_Name
XID_Start Numeric_Type  
Pattern_Syntax Hex_Digit  
Pattern_White_Space ASCII_Hex_Digit  


5.3.1 Contributory Properties

Contributory properties contain sets of exceptions used in the generation of other properties derived from them. The contributory properties specifically concerned with identifiers and casing contribute to the maintenance of stability guarantees for properties and/or to invariance relationships between related properties. Other contributory properties are simply defined as a convenience for property derivation.

Most contributory properties have names using the pattern "Other_XXX" and are used to derive the corresponding "XXX" property. For example, the Other_Alphabetic property is used in the derivation of the Alphabetic property.

Contributory properties are typically defined in PropList.txt and the corresponding derived property is then listed in DerivedCoreProperties.txt.

Jamo_Short_Name is an unusual contributory property, both in terms of its name and how it is used. It is defined in its own property file, Jamo.txt, and is used to derive the Name property value for Hangul syllable characters, according to the rules spelled out in Section 3.12, "Conjoining Jamo Behavior" in [Unicode].

Contributory properties are incomplete by themselves and are not intended for independent use. For example, an API returning Unicode property values should implement the derived core properties such as Alphabetic or Default_Ignorable_Code_Point, rather than the corresponding contributory properties, Other_Alphabetic or Other_Default_Ignorable_Code_Point.

5.4 Case and Case Mapping

Case for bicameral scripts and case mapping of characters are complicated topics in the Unicode Standard—both because of their inherent algorithmic complexity and because of the number of characters and special edge cases involved.

This section provides a brief roadmap to discussions about these topics, and specifications and definitions in the standard, as well as explaining which case-related properties are defined in the UCD.

Section 3.13, "Default Case Algorithms" in [Unicode] provides formal definitions for case-related concepts (cased, case-ignorable, ...), for case conversion (toUppercase(X), ...), and for case detection (isUppercase(X), ...). It also provides the formal definition of caseless matching for the standard, taking normalization into account.

Section 4.2, "Case—Normative", in [Unicode] introduces case and case mapping properties. Table 4-1, "Sources for Case Mapping Information", describes the kind of case-related information that is available in various data files of the UCD. The table below lists those data files again, giving the explicit list of case-related properties defined in each. The link on each property leads its description in the Property Table above.

UCD Files and Case Properties
File Name Case Properties
UnicodeData.txt Simple_Uppercase_Mapping, Simple_Lowercase_Mapping, Simple_Titlecase_Mapping
SpecialCasing.txt Uppercase_Mapping, Lowercase_Mapping, Titlecase_Mapping
CaseFolding.txt Simple_Case_Folding, Case_Folding
DerivedCoreProperties.txt Uppercase, Lowercase
PropList.txt Soft_Dotted, Other_Uppercase, Other_Lowercase

For compatibility with existing parsers, UnicodeData.txt only contains case mappings for characters where they constitute one-to-one mappings; it also omits information about context-sensitive case mappings. Information about these special cases can be found in the separate data file, SpecialCasing.txt, expressed as separate properties.

Section 5.18, "Case Mappings", in [Unicode] discusses various implementation issues for handling case, including language-specific case mapping, as for Greek and for Turkish. That section also describes case folding in particular detail.

The special casing conditions associated with case mapping for Greek, Turkish, and Lithuanian are specified in an additional field in SpecialCasing.txt. For example, the lowercase mapping for sigma in Greek varies according to its position in a word. The condition list does not constitute a formal character property in the UCD, because it is a statement about the context of occurrence of casing behavior for a character or characters, rather than a semantic attribute of those characters. Note that versions of the UCD from Version 3.2.0 to Version 5.0.0 did list property aliases for Special_Case_Condition (scc), but this was determined to be an error when the UCD was analyzed for representation in XML; consequently, the Special_Case_Condition property aliases were removed as of Version 5.1.0.

Caseless matching is of particular concern for a number of text processing algorithms, so is also discussed at some length in UAX #31: Unicode Identifier and Pattern Syntax [UAX31] and in UTS #10: Unicode Collation Algorithm [UTS10].

Further information about locale-specific casing conventions can be found in the Unicode Common Locale Data Repository [CLDR].

5.5 Property Value Lists

The following subsections give summaries of property values for certain Enumeration properties. Other property values are documented in other, topically-specific annexes; for example, the Line_Break property values are documented in UAX #14: Unicode Line Breaking Algorithm [UAX14] and the various segmentation-related property values are documented in UAX #29: Unicode Text Segmentation [UAX29].

5.5.1 General Category Values

The General_Category property of a code point provides for the most general classification of that code point. It is usually determined based on the primary characteristic of the assigned character for that code point. For example, is the character a letter, a mark, a number, punctuation, or a symbol, and if so, of what type? Other General_Category values define the classification of code points which are not assigned to regular graphic characters, including such statuses as private-use, control, surrogate code point, and reserved unassigned.

Many characters have multiple uses, and not all such cases can be captured entirely by the General_Category value. For example, the General_Category value of Latin, Greek, or Hebrew letters does not attempt to cover (or preclude) the numerical use of such letters as Roman numerals or in other numerary systems. Conversely, the General_Category of ASCII digits 0..9 as Nd (decimal digit) neither attempts to cover (or preclude) the occasional use of these digits as letters in various orthographies. The General_Category is simply the first-order, most usual categorization of a character.

For more information about the General_Category property, see Chapter 4 in [Unicode].

The values in the General_Category field in UnicodeData.txt make use of the short, abbreviated property value aliases for General_Category. For convenience in reference, the General_Category Values table below lists all the abbreviated and long value aliases for General_Category values, reproduced from PropertyValueAliases.txt, along with a brief description of each category.

General_Category Values
Abbr Long Description
Lu Uppercase_Letter an uppercase letter
Ll Lowercase_Letter a lowercase letter
Lt Titlecase_Letter a digraphic character, with first part uppercase
Lm Modifier_Letter a modifier letter
Lo Other_Letter other letters, including syllables and ideographs
Mn Nonspacing_Mark a nonspacing combining mark (zero advance width)
Mc Spacing_Mark a spacing combining mark (positive advance width)
Me Enclosing_Mark an enclosing combining mark
Nd Decimal_Number a decimal digit
Nl Letter_Number a letterlike numeric character
No Other_Number a numeric character of other type
Pc Connector_Punctuation a connecting punctuation mark, like a tie
Pd Dash_Punctuation a dash or hyphen punctuation mark
Ps Open_Punctuation an opening punctuation mark (of a pair)
Pe Close_Punctuation a closing punctuation mark (of a pair)
Pi Initial_Punctuation an initial quotation mark
Pf Final_Punctuation a final quotation mark
Po Other_Punctuation a punctuation mark of other type
Sm Math_Symbol a symbol of primarily mathematical use
Sc Currency_Symbol a currency sign
Sk Modifier_Symbol a non-letterlike modifier symbol
So Other_Symbol a symbol of other type
Zs Space_Separator a space character (of various non-zero widths)
Zl Line_Separator U+2028 LINE SEPARATOR only
Zp Paragraph_Separator U+2029 PARAGRAPH SEPARATOR only
Cc Control a C0 or C1 control code
Cf Format a format control character
Cs Surrogate a surrogate code point
Co Private_Use a private-use character
Cn Unassigned a reserved unassigned code point or a noncharacter

Note that the value gc=Cn does not actually occur in UnicodeData.txt, because that data file does not list unassigned code points.

Characters with the quotation-related General_Category values Pi or Pf may behave like opening punctuation (gc=Ps) or closing punctuation (gc=Pe), depending on usage and quotation conventions.

The symbol "L&" is used to stand for any combination of uppercase, lowercase or titlecase letters (Lu, Ll, or Lt), in the first part of comments in the data files. The LC value for the General_Category property, as documented in PropertyValueAliases.txt also stands for uppercase, lowercase or titlecase letters.

The Unicode Standard does not assign non-default property values to control characters (gc=Cc), except for certain well-defined exceptions involving the Unicode Bidirectional Algorithm, the Unicode Line Breaking Algorithm, and Unicode Text Segmentation. Also, implementations will usually assign behavior to certain line breaking control characters—most notably U+000D and U+000A (CR and LF)—according to platform conventions. See Section 5.8 "Newline Guidelines" in [Unicode] for more information.

5.5.2 Bidirectional Class Values

The values in the Bidi_Class field in UnicodeData.txt make use of the short, abbreviated property value aliases for Bidi_Class. For convenience in reference, the Bidi_Class Values table below lists all the abbreviated and long value aliases for Bidi_Class values, reproduced from PropertyValueAliases.txt, along with a brief description of each category.

Bidi_Class Values
Abbr Long Description
L Left_To_Right any strong left-to-right character
LRE Left_To_Right_Embedding U+202A: the LR embedding control
LRO Left_To_Right_Override U+202D: the LR override control
R Right_To_Left any strong right-to-left (non-Arabic-type) character
AL Arabic_Letter any strong right-to-left (Arabic-type) character
RLE Right_To_Left_Embedding U+202B: the RL embedding control
RLO Right_To_Left_Override U+202E: the RL override control
PDF Pop_Directional_Format U+202C: terminates an embedding or override control
EN European_Number any ASCII digit or Eastern Arabic-Indic digit
ES European_Separator plus and minus signs
ET European_Terminator a terminator in a numeric format context, includes currency signs
AN Arabic_Number any Arabic-Indic digit
CS Common_Separator commas, colons, and slashes
NSM Nonspacing_Mark any nonspacing mark
BN Boundary_Neutral most format characters, control codes, or noncharacters
B Paragraph_Separator various newline characters
S Segment_Separator various segment-related control codes
WS White_Space spaces
ON Other_Neutral most other symbols and punctuation marks

Please refer to UAX #9: The Unicode Bidirectional Algorithm [UAX9] for an an explanation of the significance of these values when formatting bidirectional text.

5.5.3 Character Decomposition Mapping

The value of the Decomposition_Mapping property for a character is provided in field 5 of UnicodeData.txt. This is a string property, consisting of a sequence of one or more Unicode code points. The default value of the Decomposition_Mapping property is the code point of the character itself. The use of the default value for a character is indicated by leaving field 5 empty in UnicodeData.txt. Informally, the value of the Decomposition_Mapping property for a character is known simply as its decomposition mapping. When a character's decomposition mapping is other than the default value, the decomposition mapping is printed out explicitly in the names list for the Unicode code charts.

The prefixed tags supplied with a subset of the decomposition mappings generally indicate formatting information. Where no such tag is given, the mapping is canonical. Conversely, the presence of a formatting tag also indicates that the mapping is a compatibility mapping and not a canonical mapping. In the absence of other formatting information in a compatibility mapping, the tag is used to distinguish it from canonical mappings.

In some instances a canonical mapping or a compatibility mapping may consist of a single character. For a canonical mapping, this indicates that the character is a canonical equivalent of another single character. For a compatibility mapping, this indicates that the character is a compatibility equivalent of another single character.

The compatibility formatting tags used in the UCD are listed in the table below:

Compatibility Formatting Tags
Tag Description
<font> Font variant (for example, a blackletter form)
<noBreak> No-break version of a space or hyphen
<initial> Initial presentation form (Arabic)
<medial> Medial presentation form (Arabic)
<final> Final presentation form (Arabic)
<isolated> Isolated presentation form (Arabic)
<circle> Encircled form
<super> Superscript form
<sub> Subscript form
<vertical> Vertical layout presentation form
<wide> Wide (or zenkaku) compatibility character
<narrow> Narrow (or hankaku) compatibility character
<small> Small variant form (CNS compatibility)
<square> CJK squared font variant
<fraction> Vulgar fraction form
<compat> Otherwise unspecified compatibility character

Note: There is a difference between decomposition and the Decomposition_Mapping property. The Decomposition_Mapping property is a string property whose values (mappings) are defined in UnicodeData.txt, while the decomposition (also termed "full decomposition") is defined in Section 3.7, "Decomposition" in [Unicode] to use those mappings recursively.

Starting from Unicode 2.1.9, the decomposition mappings in UnicodeData.txt can be used to derive the full decomposition of any single character in canonical order, without the need to separately apply the Canonical Ordering Algorithm. However, canonical ordering of combining character sequences must still be applied in decomposition when normalizing source text which contains any combining marks.

The normalization of Hangul conjoining jamos and of Hangul syllables depends on algorithmic mapping, as specified in Section 3.12, "Conjoining Jamo Behavior" in [Unicode]. That algorithm specifies the full decomposition of all precomposed Hangul syllables, but effectively it is equivalent to the recursive application of pairwise decomposition mappings, as for all other Unicode characters. Formally, the Decomposition_Mapping property value for a Hangul syllable is the pairwise decomposition and not the full decomposition.

Each character with the Hangul_Syllable_Type value LVT will have a Decomposition_Mapping consisting of a character with an LV value and a character with a T value. Thus for U+CE31 the Decomposition_Mapping is <U+CE20, U+11B8>, rather than <U+110E, U+1173, U+11B8>.

5.5.4 Canonical Combining Class Values

The values in the Canonical_Combining_Class field in UnicodeData.txt are numerical values used in the Canonical Ordering Algorithm. Some of those numerical values also have explicit symbolic labels as property value aliases, to make their intended application more understandable. For convenience in reference, the Canonical_Combining_Class Values table below lists all the long symbolic aliases for Canonical_Combining_Class values, reproduced from PropertyValueAliases.txt, along with a brief description of each category.

Canonical_Combining_Class Values
Value Long Description
0 Not_Reordered Spacing and enclosing marks; also many vowel and consonant signs, even if nonspacing
1 Overlay Marks which overlay a base letter or symbol
7 Nukta Diacritic nukta marks in Brahmi-derived scripts
8 Kana_Voicing Hiragana/Katakana voicing marks
9 Virama Viramas
10   Start of fixed position classes
199   End of fixed position classes
200 Attached_Below_Left Marks attached at the bottom left
202 Attached_Below Marks attached directly below
204   Marks attached at the top right
208   Marks attached to the left
210   Marks attached to the right
212   Marks attached at the top left
214   Marks attached directly above
216 Attached_Above_Right Marks attached at the top right
218 Below_Left Distinct marks at the bottom left
220 Below Distinct marks directly below
222 Below_Right Distinct marks at the bottom right
224 Left Distinct marks to the left
226 Right Distinct marks to the right
228 Above_Left Distinct marks at the top left
230 Above Distinct marks directly above
232 Above_Right Distinct marks at the top right
233 Double_Below Distinct marks subtending two bases
234 Double_Above Distinct marks extending above two bases
240 Iota_Subscript Greek iota subscript only

Some of the Canonical_Combining_Class values in the table are not currently used for any characters but are specified here for completeness. Some values do not have long symbolic aliases, but these two sets are not congruent. Do not assume that absence of a long symbolic alias implies non-use of a particular Canonical_Combining_Class. See DerivedCombiningClass.txt for a complete listing of the use of Canonical_Combining_Class values for any particular version of the UCD.

Combining marks with ccc=224 (Left) follow their base character in storage, as for all combining marks, but are rendered visually on the left side of them. Note that for all past versions of the UCD and continuing with this version of the UCD, only two tone marks used in certain notations for Hangul syllables have ccc=224. Those marks are actually rendered visually on the left side of the preceding grapheme cluster, in the case of Hangul syllables resulting from sequences of conjoining jamos.

Those few instances of combining marks with ccc=Left should be distinguished from the far more numerous examples of left-side vowel signs and vowel letters in Brahmi-derived scripts. The Canonical_Combining_Class value is zero (Not_Reordered) for both ordinary, left-side (reordrant) vowel signs such as U+093F DEVANAGARI VOWEL SIGN I and for Thai-style left-side (Logical_Order_Exception=Yes) vowel letters such as U+0E40 THAI CHARACTER SARA E. The "Not_Reordered" of ccc=Not_Reordered refers to the behavior of the character in terms of the Canonical Ordering Algorithm as part of the definition of Unicode Normalization; it does not refer to any issues of visual reordering of glyphs involved in display and rendering. See Section 3.11, "Canonical Ordering Behavior" in [Unicode].

5.5.5 Decompositions and Normalization

Decomposition is specified in Chapter 3, Conformance of [Unicode]. UAX #15, Unicode Normalization Forms [UAX15] specifies the interaction between decomposition and normalization. That annex specifies how the decompositions defined in UnicodeData.txt are used to derive normalized forms of Unicode text.

A number of derived properties related to Unicode normalization are called the "Quick_Check" properties. These are defined to enable various optimizations for implementations of normalization, as explained in Section 14, "Detecting Normalization Forms", in UAX #15, Unicode Normalization Forms [UAX15]. The values for the four Quick_Check properties for all code points are listed in DerivedNormalizationProps.txt. The interpretations of the possible property values are summarized in the table below:

Quick_Check Property Values
Property Value Description
NFC_QC, NFKC_QC, NFD_QC, NFKD_QC No Characters that cannot ever occur in the respective normalization form.
NFC_QC, NFKC_QC Maybe Characters that may occur in the respective normalization, depending on the context.
NFC_QC, NFKC_QC, NFD_QC, NFKD_QC Yes All other characters. This is the default value for Quick_Check properties.


5.6 Property and Property Value Aliases

Both Unicode character properties themselves and their values are given symbolic aliases. The formal lists of aliases are provided so that well-defined symbolic values are available for XML formats of the UCD data, for regular expression property tests, and for other programmatic textual descriptions of Unicode data. The aliases for properties are defined in PropertyAliases.txt. The aliases for property values are defined in PropertyValueAliases.txt.

Alias Files in the UCD
File Name Status Description
PropertyAliases.txt N Names and abbreviations for properties
PropertyValueAliases.txt N Names and abbreviations for property values

Aliases are defined as ASCII-compatible identifiers, using only uppercase or lowercase A-Z, digits, and underscore "_". Case is not significant when comparing aliases, but the preferred form used in the data files for longer aliases is to titlecase them.

Aliases may be translated in appropriate environments, and additional aliases may be useful in certain contexts. There is no requirement that only the aliases defined in the alias files of the UCD be used when referring to Unicode character properties or their values; however, their use is recommended for interoperability in data formats or in programmatic contexts.

5.6.1 Property Aliases

In PropertyAliases.txt, the first field specifies an abbreviated symbolic name for the property, and the second field specifies the long symbolic name for the property. These are the preferred aliases. Additional aliases for a few properties are specified in the third or subsequent fields.

The long symbolic name alias is self-descriptive, and is treated as the official name of a Unicode character property. For clarity it is used whenever possible when referring to that property in this annex and elsewhere in the Unicode Standard. For example: "The Line_Break property is discussed in UAX #14, Unicode Line Breaking Algorithm [UAX14]."

The abbreviated symbolic name alias is short and less mnemonic, but is useful for expressions such as "lb=BA" in data or in other contexts where the meaning is clear.

The property aliases specified in PropertyAliases.txt constitute a unique name space. When using these symbolic values, no alias for one property will match an alias for another property.

5.6.2 Property Value Aliases

In PropertyValueAliases.txt, the first field contains the abbreviated alias for a Unicode property, the second field specifies an abbreviated symbolic name for a value of that property, and the third field specifies the long symbolic name for that value of that property. These are the preferred aliases. Additional aliases for some property values may be specified in the fourth or subsequent fields. For example, for binary properties, the abbreviated alias for the True value is "Y", and the long alias is "Yes", but each entry also specifies "T" and "True" as additional aliases for that value, as shown in the table below:

Binary Property Value Aliases
Long Abbreviated Other Aliases
Yes Y True, T
No N False, F

Not every property value has an associated alias. Property value aliases are typically supplied for catalog and enumeration properties, which have well-defined, enumerated values. It does not make sense to specify property value aliases, for example, for the Numeric_Value property, whose value could be any number, or for a string property such as Simple_Lowercase_Mapping, whose values are mappings from one code point to another.

The Canonical_Combining_Class property requires special handling in PropertyValueAliases.txt. The values of this property are numeric, but they comprise a closed, enumerated set of values. The more important of those values are given symbolic name aliases. In PropertyValueAliases.txt, the second field provides the numeric value, while the third field contains the abbreviated symbolic name alias and the fourth field contains the long symbolic name alias for that numeric value. For example:

ccc; 230; A    ; Above
ccc; 232; AR   ; Above_Right

Taken by themselves, property value aliases do not constitute a unique name space. The abbreviated aliases, in particular, are often re-used as aliases for values for different properties. All of the binary property value aliases, for example, make use of the same "Y", "Yes", "T", "True" symbols. Property value aliases may also overlap the symbols used for property aliases. For example, "Sc" is the abbreviated alias for the "Currency_Symbol" value of the General_Category value, but it is also the abbreviated alias for the Script property. However, the aliases for values for any single property are always unique within the context of that property. What that means is that expressions that combine a property alias and a property value alias, such as "lb=BA" or "gc=Sc" always refer unambiguously just to one value of one given property, and will not match any other value of any other property.

The property value alias entries for three properties, Age, Block, and Joining_Group, make use of a special metavalue "n/a" in the field for the abbreviated alias. This should be understood as meaning that no abbreviated alias is defined for that value for that property, rather than as an alias per se.

In a few cases, because of longstanding legacy practice in referring to values of a property by short identifiers, the abbreviated alias and the long alias are the same. This can be seen, for example, in some property value aliases for the Line_Break property and the Grapheme_Cluster_Break property.

5.7 Matching Rules

When matching Unicode character property names and values, it is strongly recommended that all Property and Property Value Aliases be recognized. For best results in matching, rather than using exact binary comparisons, the following loose matching rules should be observed.

Numeric Property Values

For all numeric properties, and for properties such as Unicode_Radical_Stroke which are constructed from combinations of numeric values, use loose matching rule UAX44-LM1 when comparing property values.

UAX44-LM1. Apply numeric equivalences.

Character Names

Unicode character names constitute a special case. Formally, they are values of the Name property. While each Unicode character name for an assigned character is guaranteed to be unique, names are assigned in such a way that the presence or absence of spaces cannot be used to distinguish them. Furthermore, implementations sometimes create identifiers from Unicode character names by inserting underscores for spaces. For best results in comparing Unicode character names, use loose matching rule UAX44-LM2.

UAX44-LM2. Ignore case, whitespace, underscore ('_'), and all medial hyphens except the hyphen in U+1180 HANGUL JUNGSEONG O-E.

Symbolic Values

Property aliases and property value aliases are symbolic values. When comparing them, use loose matching rule UAX44-LM3.

UAX44-LM3. Ignore case, whitespace, underscore ('_'), and hyphens.

Loose matching is generally appropriate for the property values of Catalog, Enumeration, and Binary properties, which have symbolic aliases defined for their values. Loose matching should not be done for the property values of String properties, which do not have symbolic aliases defined for their values; exact matching for String property values is important, as case distinctions or other distinctions in those values may be significant.

5.8 Invariants

Property values in the UCD may be subject to correction in subsequent versions of the standard, as errors are found. Also, some multi-valued properties such as Line_Break or Word_Break may have additional values defined for them. However, some property values and some aspects of the file formats are considered invariant. This section documents such invariants.

5.8.1 Character Property Invariants

All formally guaranteed invariants for properties or property values are described in the Unicode Character Encoding Stability Policy [Stability]. That policy and the list of invariants it enumerates are maintained outside the context of the Unicode Standard per se. They are not part of the standard, but rather are constraints on what can and cannot change in the standard between versions, and on what decisions the Unicode Technical Committee can and cannot take regarding the standard.

In addition to the formally guaranteed invariants described in the Unicode Character Encoding Stability Policy, this section notes a few additional points regarding character property invariants in the UCD.

Some character properties are simply considered immutable: once assigned, they are never changed. For example, a character's name is immutable, because of its importance in exact identification of the character. The Canonical_Combining_Class and Decomposition_Mapping of a character are immutable, because of their important to the stability of the Unicode Normalization Algorithm [UAX15].

The list of immutable character properties is shown in the table below:

Immutable Properties
Property Name Abbr Name
Name na
Jamo_Short_Name jsn
Canonical_Combining_Class ccc
Decomposition_Mapping dm
Pattern_Syntax Pat_Syn
Pattern_White_Space Pat_WS

In some cases, a property is not immutable, but the list of possible values that it can have is considered invariant. For example, while at least some General_Category values are subject to change and correction, the enumerated set of possible values that the General_Category property can have is fixed and cannot be added to in the future.

All characters other than those of General_Category M* are guaranteed to have Canonical_Combining_Class=0. Currently it is also true that all characters other than those of General_Category Mn have Canonical_Combining_Class=0. However, the more constrained statement is not a guaranteed invariant; it is possible that some new character of General_Category Me or Mc could be given a non-zero value for Canonical_Combining_Class in the future.

In Unicode 4.0 and thereafter, the General_Category value Decimal_Number (Nd), and the Numeric_Type value Decimal (de) are defined to be co-extensive; that is, the set of characters having General_Category=Nd will always be the same as the set of characters having NumericType=de.

5.8.2 UCD File Format Invariants

There are also some constraints on allowable change in the file formats for UCD files. In general, the file format conventions are changed as little as possible, to minimize the impact on implementations which parse the machine-readable data files. However, some of the constraints on allowable file format change go beyond conservatism in format and instead have the status of invariants. These guarantees apply in particular to UnicodeData.txt, the very first data file associated with the UCD.

The number and order of the fields in UnicodeData.txt is fixed. Any additional information about character properties to be added to the UCD in the future will appear in separate data files, rather than being added as an additional field to UnicodeData.txt or by reinterpretation of any of the existing fields.

5.8.3 Invariants in Implementations

Applications may wish to take the various character property and file format invariants into account when choosing how to implement character properties.

The Canonical_Combining_Class offers a good example. The character property invariants regarding Canonical_Combining_Class guarantee that values, once assigned, will never change, and that all values used will be in the range 0..255. This means that the Canonical_Combining_Class can be safely implemented in an unsigned byte and that any value stored in a table for an existing character will not need to be updated dynamically for a later version.

In practice, for Canonical_Combining_Class far fewer than 256 values are used. Unicode 3.0 used 53 values; Unicode 3.1 through Unicode 4.1 used 54 values; and Unicode 5.0 through Unicode 5.1 used 55 values. New, non-zero Canonical_Combining_Class values are seldom added to the standard. (For details about this history, see DerivedCombiningClass.txt.) Implementations may take advantage of this fact for compression, because only the ordering of the non-zero values, and not their absolute values, matters for the Canonical Ordering Algorithm. In principle, it would be possible for up to 256 values to be used in the future, but the chances of the actual number of values exceeding 128 are remote at this point. There are implementation advantages in restricting the number of internal class values to 128—for example, the ability to use signed bytes without implicit widening to ints in Java.

5.9 Validation

KWW NOTE: This section still needs more work. The table is also structured infelicitously in my opinion. Either we need a complete list of all the properties, each with an explicit syntax specified for them (along the lines now done in UAX #38 for the Unihan properties), or we could refactor the discussion (my preference) as follows: First provide a section classifying the value domains for properties into pattern types, providing a table which lists all the properties associated with each pattern type, and then give another table that shows the regex used for each pattern type. That would be both much easier to understand and likely more correct.

The table below appears to have errors and omissions in it still. Age is underspecified, and should be done more tightly. The expression for Unicode_1_Name is probably too tight, by contrast. The ISO_Comment field is incorrect. And the regex for the Block and the Script properties should not be the same. There may be other problems, as well.

The property values for many of the Unicode character properties have a regular syntax that makes it possible to validate the values in the UCD data files by means of regular expressions. Regular expressions for a number of the Catalog, String and Miscellaneous type properties in the UCD are provided in the table below. These expressions use Perl syntax, but may be of course be converted to other formal conventions for use with other regular expression engines.

Regular Expressions for Property Values
Abbr Name Regex for Allowable Values
age Age /([0-9]+\.[0-9]|unassigned)/
nv Numeric_Value /-?[0-9]+\.[0-9]+/ Field 2
/-?[0-9]+(\[0-9]+)?/ Field 3
blk Block /[a-zA-Z0-9]+([_\ ][a-zA-Z0-9]+)*/
sc Script
dm Decomposition_Mapping /[\x{0}-\x{10FFFF}]+/
cf Case_Folding /[\x{0}-\x{10FFFF}]+/
lc Lowercase_Mapping
tc Titlecase_Mapping
uc Uppercase_Mapping
sfc Simple_Case_Folding /[\x{0}-\x{10FFFF}]/
slc Simple_Lowercase_Mapping
stc Simple_Titlecase_Mapping
suc Simple_Uppercase_Mapping
bmg Bidi_Mirroring_Glyph /[\x{0}-\x{10FFFF}]?/
isc ISO_Comment /([A-Z0-9]+(([-\ ]|\ -|-\ )[A-Z0-9]+)*|\<CONTROL\>)?/
na1 Unicode_1_Name /([A-Z0-9]+(([-\ ]|\ -|-\ )[A-Z0-9]+)*(\ \((CR|FF|LF|NEL)\))?)?/
na Name /([A-Z0-9]+(([-\ ]|\ -|-\ )[A-Z0-9]+)*|\<CONTROL\>)?/


6 Test Files

The UCD contains a number of test data files. Those provide data in standard formats which can be used to test implementations of Unicode algorithms. The test data files distributed with this version of the UCD are listed in the table below.

Unicode Algorithm Test Data Files
File Name Specification Status Unicode Algorithm
NormalizationTest.txt [UAX15] N Unicode Normalization Algorithm
LineBreakTest.txt [UAX14] N Unicode Line Breaking Algorithm
GraphemeBreakTest.txt [UAX29] N Grapheme Cluster Boundary Determination
WordBreakTest.txt [UAX29] N Word Boundary Determination
SentenceBreakTest.txt [UAX29] N Sentence Boundary Determination

The normative status of these test files reflects their use to determine the correctness of implementations claiming conformance to the respective algorithms listed in the table. There is no requirement that any particular Unicode implementation also implement the Unicode Line Breaking Algorithm, for example, but if it implements that algorithm correctly, it should be able to replicate the test case results specified in the data entries in LineBreakTest.txt.

6.1 NormalizationTest.txt

This file contains data which can be used to test an implementation of the Unicode Normalization Algorithm. (See [UAX15].)

The data file has a Unicode string in the first field (which may consist of just a single code point). The next four fields then specify the expected output results of converting that string to Unicode Normalization Forms NFC, NFD, NFKC, and NFKD, respectively. There are many tricky edge cases included in the input data, to ensure that implementations have correctly implemented some of the more complex subtleties of the Unicode Normalization Algorithm.

The header section of NormalizationTest.txt provides additional information regarding the normalization invariant relations that any conformant implementation should be able to replicate.

The Unicode Normalization Algorithm is not tailorable. Conformant implementations should be expected to produce results as specified in NormalizationTest.txt and should not deviate from those results.

6.2 Segmentation Test Files and Documentation

LineBreakTest.txt, located in the auxiliary directory of the UCD, contains data which can be used to test an implementation of the Unicode Line Breaking Algorithm. (See [UAX14].) The header of that file specifies the data format and the use of the test data to specify line break opportunities. Note that non-ASCII characters are used in this test data as field delimiters.

There is an associated documentation file, LineBreakTest.html, which displays the results of the Line Breaking Algorithm in an interactive chart form, with a documented listing of the rules.

The Unicode text segmentation test data files are also located in the auxiliary directory of the UCD. They contain data which can be used to test an implementation of the segmentation algorithms specified in [UAX29]. The headers of those file specify the data format and the use of the test data to specify text segmentation opportunities. Note that non-ASCII characters are used in this test data as field delimiters.

There are also associated documentation files, which display the results of the segmentation algorithms in an interactive chart form, with a documented listing of the rules:

Unlike the Unicode Normalization Algorithm, the Unicode Line Breaking Algorithm and the various text segmentation algorithms are tailorable, and there is every expectation that implementations will tailor these algorithms to produce results as needed. The test data files only test the default behavior of the algorithms. Testing of tailored implementations will need to modify and/or extend the test cases as appropriate to match any documented tailoring.

7 UCD Change History

This section summarizes the changes to the UCD—including its documentation files—and is organized by Unicode versions. The summary includes changes extending all the way back to Unicode 2.0.0, taken from the obsoleted UCD.html documentation file, which predates the creation of this annex. The intent is for this first consolidated version of the annex to preserve that complete prior history from UCD.html. Subsequent versions of the annex will provide only an abbreviated UCD change history section containing only the delta change information from each preceding version.

Starting from Unicode 4.0.1, references in the change history are often made to a Public Review Issue (PRI). See http://www.unicode.org/review/resolved-pri.html for more information about each of those cases.

Changes documented prior to Unicode 4.0 only covered UnicodeData.txt. From Unicode 4.0 onward, the documentation of changes includes modifications of other files as well.

Unicode 5.2.0



Common file changes:


Changes in specific files:


Unicode 5.1.0



Changes in specific files:

Appropriate data files were updated to include the 1,624 new characters added in Unicode 5.1.

Unicode 5.0.0


Common file changes:

In many data files an explicit default property assignment range was added (in a machine-readable comment line), to assist implementations in assigning values for code points not otherwise listed in the data file.

Changes in specific files:

Appropriate data files were updated to include the 1,369 new characters added in Unicode 5.0.

Two new data files, NameAliases.txt and NamedSequencesProv.txt, were added to the UCD.

Unicode 4.1.0



Common file changes:

All remaining files not corrected for Unicode 4.0.1 have had their headers updated to explicitly point to Terms of Use. The headers have also been synchronized somewhat to share a more common format for file version, date, and pointers to documentation. The major exception is UnicodeData.txt, which for legacy reasons, has no header.

Changes in specific files:

Appropriate data files were updated to include the 1,273 new characters added in Unicode 4.1.0.

The description of the Unihan properties was separated out from UCD.html, extensively revised, and moved into a new documentation file, Unihan.html.

Unicode 4.0.1


Common file changes:

Some property values have different casing (upper versus lower) for consistency between the data files and the PropertyValueAlias file. There are some additional changes in comments:

Changes in specific files:

Unicode 4.0.0


For details on changes made to the UCD for Unicode 4.0.0, see Section D.4, "Changes from Unicode Version 3.2 to Version 4.0" in Appendix D of The Unicode Standard, Version 4.0.

Common file changes:

Default property values were more precisely defined, for code points not explicitly listed in the data files.

Changes in specific files:

Unicode 3.2.0


For details on changes made to the UCD for Unicode 3.2.0, see Section D.3, "Changes from Unicode Version 3.1 to Version 3.2" in Appendix D of The Unicode Standard, Version 4.0.

Changes in specific files:

Appropriate data files were updated to include the 1,016 new characters added in Unicode 3.2.0.

Unicode 3.1.1

Changes in specific files:

Unicode 3.1.0


For details on changes made to the UCD for Unicode 3.1.0, see Section D.2, "Changes from Unicode Version 3.0 to Version 3.1" in Appendix D of The Unicode Standard, Version 4.0.

Changes in specific files:

Appropriate data files were updated to include the 2,237 new entries, to cover new individual characters and the new ranges of Unified CJK Ideographs encoded in Unicode 3.1.0.

Unicode 3.0.1


Changes in specific files:

Unicode 3.0.0

Modifications made for Version 3.0.0 of UnicodeData.txt include many new characters and a number of property changes. These are summarized in Appendix D of The Unicode Standard, Version 3.0.

Unicode 2.1.9

Modifications made for Version 2.1.9 of UnicodeData.txt include:

Unicode 2.1.8

Modifications made for Version 2.1.8 of UnicodeData.txt include:

Version 2.1.7

This version was for internal change tracking only, and never publicly released.

Version 2.1.6

This version was for internal change tracking only, and never publicly released.

Unicode 2.1.5

Modifications made for Version 2.1.5 of UnicodeData.txt include:

Version 2.1.4

This version was for internal change tracking only, and never publicly released.

Version 2.1.3

This version was for internal change tracking only, and never publicly released.

Unicode 2.1.2

Modifications made in updating UnicodeData.txt to Version 2.1.2 for the Unicode Standard, Version 2.1 (from Version 2.0) include:

Version 2.1.1

This version was for internal change tracking only, and never publicly released.

Unicode 2.0.0

The modifications made in updating UnicodeData.txt for the Unicode Standard, Version 2.0 include:


Mark Davis and Ken Whistler are the authors of the initial version and have added to and maintained the text of this annex. Julie Allen provided editorial suggestions for improvement of the text. Over the years, many members of the UTC have participated in the review of the UCD and its documentation.


For references for this annex, see Unicode Standard Annex #41, “Common References for Unicode Standard Annexes.”


For details of the change history, see the online copy of this annex at http://www.unicode.org/reports/tr44/.

The following summarizes modifications from previous revisions of this annex.

Revision 3

  • Proposed update for Unicode 5.2.0.
  • Completely reorganized and rewritten, to include all the content from the obsoleted UCD.html.

Revision 2

  • Initial approved version for Unicode 5.1.0.

Revision 1

  • Initial draft.