Unicode font

Fonts which support a wide range of Unicode scripts and Unicode symbols are sometimes referred to as "pan-Unicode fonts", although as the maximum number of glyphs that can be defined in a TrueType font is restricted to 65,535, it is not possible for a single TrueType font to provide individual glyphs for all defined Unicode characters (172,808 characters, with Unicode 18.0). This article lists some widely used Unicode fonts (those shipped with an operating system or produced by a well-known commercial font company) that support a comparatively large number and broad range of Unicode characters.

Background

The Unicode standard does not specify or create any font (typeface), a collection of graphical shapes called glyphs, itself. Rather, it defines the abstract characters as a specific number (known as a code point) and also defines the required changes of shape depending on the context the glyph is used in (e.g., combining characters, precomposed characters and letter-diacritic combinations). The choice of font, which governs how the abstract characters in the Universal Coded Character Set (UCS) are converted into a bitmap or vector output that can then be viewed on a screen or printed, is left up to the user. If a font is chosen which does not contain a glyph for a code point used in the document, it typically displays a question mark, a box, or some other substitute character.

Computer fonts use various techniques to display characters or glyphs. A bitmap font contains a grid of dots known as pixels forming an image of each glyph in each face and size. Outline fonts (also known as vector fonts) use drawing instructions or mathematical formulae to describe each glyph. Stroke fonts use a series of specified lines (for the glyph's border) and additional information to define the profile, or size and shape of the line in a specific face and size, which together describe the appearance of the glyph.

Fonts also include embedded special orthographic rules to output certain combinations of letterforms (and alternative symbols for the same letter) be combined into special ligature forms (mixed characters). Operating systems, web browsers (user agent), and other software that extensively use typography, use a font to display text on the screen or print media, and can be programmed to use those embedded rules. Alternatively, they may use external script-shaping technologies (rendering technology or “smart font” engine), and they can also be programmed to use either a large Unicode font, or use multiple different fonts for different characters or languages.

No single "Unicode font" includes all the characters defined in the present revision of ISO 10646 (Unicode) standard, as more and more languages and characters are continually added to it, and common font formats cannot contain more than 65,535 glyphs (about half the number of characters encoded in Unicode). As a result, font developers and foundries incorporate new characters in newer versions or revisions of a font, or in separate auxiliary fonts intended specifically for particular languages.

UCS has over 1.1 million code points, but only the first 65,536 (the Plane 0: Basic Multilingual Plane, or BMP) had entered into common use before 2000.

See the Unicode planes article for more information on other planes, including: Plane 1: Supplementary Multilingual Plane (SMP), Plane 2: Supplementary Ideographic Plane (SIP), Plane 14: Supplementary Special-purpose Plane (SSP), Plane 15 and 16: reserved for Private Use Areas (PUA).

The first Unicode fonts (with very large character sets and supporting many Unicode blocks) were Lucida Sans Unicode (released March 1993), Unihan font (1993), and Everson Mono (1995).