Universal Character Set characters

The Unicode Consortium and the ISO/IEC JTC 1/SC 2/WG 2 jointly collaborate on the list of the characters in the Universal Coded Character Set. The Universal Coded Character Set, most commonly called the Universal Character Set (abbr. UCS, official designation: ISO/IEC 10646), is an international standard to map characters, discrete symbols used in natural language, mathematics, music, and other domains, to unique machine-readable data values. By creating this mapping, the UCS enables computer software vendors to interoperate, and transmit—interchange—UCS-encoded text strings from one to another. Because it is a universal map, it can be used to represent multiple languages at the same time. This avoids the confusion of using multiple legacy character encodings, which can result in the same sequence of codes having multiple interpretations depending on the character encoding in use, resulting in mojibake if the wrong one is chosen. UCS has a potential capacity of over 1 million characters. Each UCS character is abstractly represented by a code point, an integer between 0 and 1,114,111 (1,114,112 = 220 + 216 or 17 × 216 = 0x110000 code points), used to represent each character within the internal logic of text processing software. As of Unicode 17.0, released in September 2025, 303,808 (27%) of these code points are allocated, 159,866 (14%) have been assigned characters, 137,468 (12%) are reserved for private use, 2,048 are used to enable the mechanism of surrogates, and 66 are designated as noncharacters, leaving the remaining 810,304 (73%) unallocated. The number of encoded characters is made up as follows:

159,629 graphical characters (some of which do not have a visible glyph, but are still counted as graphical) 237 special purpose characters for control and formatting. ISO maintains the basic mapping of characters from character name to code point. Often, the terms character and code point will be used interchangeably. However, when a distinction is made, a code point refers to the integer of the character: what one might think of as its address. Meanwhile, a character in ISO/IEC 10646 includes the combination of the code point and its name, Unicode adds many other useful properties to the character set, such as block, category, script, and directionality. In addition to the UCS, the supplementary Unicode Standard, (not a joint project with ISO, but rather a publication of the Unicode Consortium,) provides other implementation details such as:

mappings between UCS and other character sets different collations of characters and character strings for different languages an algorithm for laying out bidirectional text ("the BiDi algorithm"), where text on the same line may shift between left-to-right ("LTR") and right-to-left ("RTL") a case-folding algorithm Computer software end users enter these characters into programs through various input methods, for example, physical keyboards or virtual character palettes. The UCS can be divided in various ways, such as by plane, block, character category, or character property.

Character reference overview

An HTML or XML numeric character reference refers to a character by its Universal Character Set/Unicode code point, and uses the format

&#nnnn; or

&#xhhhh; where nnnn is the code point in decimal form, and hhhh is the code point in hexadecimal form. The x must be lowercase in XML documents. The nnnn or hhhh may be any number of digits and may include leading zeros. The hhhh may mix uppercase and lowercase, though uppercase is the usual style. In contrast, a character entity reference refers to a character by the name of an entity which has the desired character as its replacement text. The entity must either be predefined (built into the markup language) or explicitly declared in a Document Type Definition (DTD). The format is the same as for any entity reference:

&name; where name is the case-sensitive name of the entity. The semicolon is required.

Planes

Unicode and ISO divide the set of code points into 17 planes, each capable of containing 65536 distinct characters or 1,114,112 total. As of 2025 (Unicode 17.0) ISO and the Unicode Consortium has only allocated characters and blocks in seven of the 17 planes. The others remain empty and reserved for future use. Most characters are currently assigned to the first plane: the Basic Multilingual Plane. This is to help ease the transition for legacy software since the Basic Multilingual Plane is addressable with just two octets. The characters outside the first plane usually have very specialized or rare use. Each plane corresponds with the value of the one or two hexadecimal digits (0—9, A—F) preceding the four final ones: hence U+24321 is in Plane 2, U+4321 is in Plane 0 (implicitly read U+04321), and U+10A200 would be in Plane 16 (hex 10 = decimal 16). Within one plane, the range of code points is hexadecimal 0000—FFFF, yielding a maximum of 65536 code points. Planes restrict code points to a subset of that range.

Blocks

Unicode adds a block property to UCS that further divides each plane into separate blocks. Each block is a grouping of characters by their use such as "mathematical operators" or "Hebrew script characters". When assigning characters to previously unassigned code points, the Consortium typically allocates entire blocks of similar characters: for example all the characters belonging to the same script or all similarly purposed symbols get assigned to a single block. Blocks may also maintain unassigned or reserved code points when the Consortium expects a block to require additional assignments. The first 256 code points in the UCS correspond with those of ISO 8859-1, the most popular 8-bit character encoding in the Western world. As a result, the first 128 characters are also identical to ASCII. Though Unicode refers to these as a Latin script block, these two blocks contain many characters that are commonly useful outside of the Latin script. In general, not all characters in a given block need be of the same script, and a given script can occur in several different blocks.

Categories Unicode assigns to every UCS character a general category and subcategory. The general categories are: letter, mark, number, punctuation, symbol, or control (in other words a formatting or non-graphical character). Types include:

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