State-of-the-art digital typographic systems have solved virtually all the demands of traditional typography and have expanded the possibilities with many new features. Three systems are in common use: OpenType, devised by Microsoft and Adobe, Apple's Apple Advanced Typography (AAT), and SIL's Graphite. The lists below provide information about OpenType and AAT features. Graphite does not have a fixed set of features; instead it provides a way for fonts to define their own features.
OpenType typographic features
The OpenType format defines a number of typographic features that a particular font may support; some software, such as Adobe InDesign or recent versions of Lua/XeTeX, gives users control of these, for example to enable fancy stylistic capital letters (swash caps) or to choose between ranging (full-height) and non-ranging (old-style, or lower-case) digits.
The following tables list the features defined in version 1.7 of the OpenType specification. The codes in the "type" column are explained after the tables.
OpenType features may be applicable only to certain language scripts or specific languages, or in certain writing modes. The features are split into several tables accordingly.
Features primarily intended for or exclusively required by South-Asian alphasyllabaries (Indic/Brahmic)
Long name
tag
type
Description
Above-base Forms
abvf
S1
Replaces the diacritic part of a vowel sign in Khmer etc., e.g. ä to aͤ
Above-base Mark Positioning
abvm
P4,5
Positions a diacritic mark on top of the base glyph
Above-base Substitutions
abvs
S4
Replaces a pair of base and top diacritic mark by a ligature, e.g. ä to æ
Below-base Forms
blwf
S4
Replaces the subscript part of a consonant compound in Khmer etc., e.g. ş to ș
Below-base Mark Positioning
blwm
P4,5
Positions a diacritic mark on top of the base glyph
Below-base Substitutions
blws
S4
Replaces a pair of base and bottom diacritic mark by a ligature, e.g. ç to cz
Pre-base Forms
pref
S4
Khmer and other similar scripts: Myanmar, Malayalam, Telugu
Pre-base Substitutions
pres
S4,5
Indic
Post-base Substitutions
psts
S4
Indic (any alphabetic?)
Post-base Forms
pstf
S4
Khmer and Gurmukhi, Malayalam
Distance
dist
P2
Adjusts horizontal positioning between glyphs
Akhand
akhn
S4
Hindi for unbreakable, forms CCV ligatures from two consecutive CV glyphs
Halant Forms
haln
S4
Uses halant forms of CV glyphs, indicating that it is read C, may include virama
Half Form
half
S4
Uses half-forms of CV glyphs, indicating that it is read as just C
Nukta Forms
nukt
S4
Add nukta (dot mark) to glyph, although this is available through Unicode characters
Obsolete ligatures to be applied at the user's discretion
Standard Ligatures
liga
S4
Replaces (by default) sequence of characters with a single ligature glyph
Positioning features intended for all scripts
Long name
tag
type
Description
Glyph Composition/Decomposition
ccmp
S4,2
Either calls a ligature replacement on a sequence of characters or replaces a character with a sequence of glyphs. Provides logic that can for example effectively alter the order of input characters.
Kerning
kern
P2,8
Fine horizontal positioning of one glyph to the next, based on the shapes of the glyphs
Mark Positioning
mark
P4,5
Fine positioning of a mark glyph to a base character
Mark-to-mark Positioning
mkmk
P6
Fine positioning of a mark glyph to another mark character
Optical Bounds
opbd
P1
Re-positions glyphs at beginning and end of line, for precise justification of text.
Left Bounds
lfbd
P1
Re-positions glyphs at end of line. Called by opbd.
Right Bounds
rtbd
P1
Re-positions glyphs at beginning of line. Called by opbd.
Special features intended for all scripts
Long name
tag
type
Description
Optical size
size
Not a lookup: feature's table provides to applications information about the appearance and intent of the font, to aid in font selection.
Ornaments
ornm
S3,1
Decorative alternates for the bullet character •
Below are listed the OpenType lookup table types, as used in the "type" column in the above tables. S stands for substitution, and P stands for positioning. Note that often a feature can be implemented by more than one type of table, and that sometimes the specification fails to explicitly indicate the table type.
Legend of substitution and positioning codes
abbrev.
type
description
S1
GSUB 1
simple substitution of one glyph with another
S2
GSUB 2
multiple substitution of one character by several glyphs
S3
GSUB 3
variant selection
S4
GSUB 4
ligatures
S5
GSUB 5
contextual substitution
S6
GSUB 6
chained contextual substitution
S7
GSUB 7
extension for GSUB tables past 64kB
S8
GSUB 8
reverse chained contextual substitution
P1
GPOS 1
positioning of single glyph
P2
GPOS 2
positioning of pair of glyphs
P3
GPOS 3
cursive attachment
P4
GPOS 4
positioning of mark glyphs relative to base
P5
GPOS 5
positioning of mark glyphs relative to ligature
P6
GPOS 6
positioning of mark glyphs relative to another mark glyph
P7
GPOS 7
contextual positioning
P8
GPOS 8
extended contextual positioning
P9
GPOS 9
extension for GPOS tables past 64kB
AAT typographic features
Features that take one value, mutual exclusive from the rest: