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Typographic features made possible using digital typographic systems have solved many of the demands placed on computer systems to replicate 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, LibreOffice/ OpenOffice, or recent versions of Lua/ XeTeX, gives users control of these features, 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. Some web browsers also support OpenType features in accordance with the CSS Fonts Module Level 3 specification, which allows OpenType features to be set directly via the font-feature-settings property, or indirectly by means of higher-level mechanisms.

The following tables list the features defined in version 1.8.1 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 above-base part of a vowel sign. For Khmer and similar scripts.
Above-base Mark Positioning abvm P4,5 Positions a mark glyph above a base glyph.
Above-base Substitutions abvs S4 Ligates a consonant with an above-mark.
Below-base Forms blwf S4 Replaces halant+consonant combination with a subscript form.
Below-base Mark Positioning blwm P4,5 Positions a mark glyph below a base glyph
Below-base Substitutions blws S4 Ligates a consonant with a below-mark.
Pre-base Forms pref S4[ disputed – discuss] Replaces halant+consonant at the end of a consonant cluster with a glyph at the beginning. Khmer, Myanmar, Malayalam, Telugu
Pre-base Substitutions pres S4,5 Ligates consonant combinations.
Post-base Substitutions psts S4 Ligates a final consonant+consonant.
Post-base Forms pstf S4 Substitutes final halant+consonant with special form. Khmer and Gurmukhi, Malayalam
Distance dist P2 Adjusts horizontal positioning between glyphs. (Always enabled, as opposed to 'kern'.)
Akhand akhn S4 Hindi for unbreakable. Ligates consonant+halant+consonant, usually only for k-ss and j-ny combinations.
Halant Forms haln S4 Replaces a glyph for final consonant+ halant.
Half Form half S4 Replaces consonant+halant with a half form, indicating it is part of a conjunct.
Nukta Forms nukt S4 Replace consonant+ nukta (dot mark) with single glyph.
Rakar Forms rkrf S4 Replaces halant+ra with a rakar glyph, indicating it is part of a conjunct.
Reph Form rphf S4 Replaces initial ra+halant with a final reph mark, indicating part of a conjunct.
Vattu Variants vatu S4 Replaces consonant+rakar combinations with a vattu variant ligature.
Conjunct Forms cjct S4 Ligates consonant+halant+consonant, indicates part of a conjunct.
Conjunct Form After Ro cfar S1 Khmer

Features primarily intended for or exclusively required by East-Asian tetragrams (Chinese, Japanese, Korean)

Long name tag type Description
Simplified Forms smpl S1 Replaces sinograms with their simplified versions, may be language dependent
Traditional Forms trad S1,3 Replaces Chinese characters with their traditional versions
Traditional Name Forms tnam S1 Japanese alternates for proper names
Expert Forms expt S1 Typographic alternatives for some Japanese tetragrams
Hojo Kanji Forms hojo Hojo alternates for Japanese tetragrams
NLC Kanji Forms nlck NLC alternates for Japanese tetragrams
JIS 78 Forms jp78 S1,3 JIS C 6226-1978 alternates for Japanese tetragrams, not accessible per Unicode
JIS 83 Forms jp83 S1 JIS X 0208-1983 alternates for Japanese tetragrams, not accessible per Unicode
JIS 90 Forms jp90 S1 JIS X 0208-1990 alternates for Japanese tetragrams, not accessible per Unicode
JIS 04 Forms jp04 JIS 2004 alternates for Japanese tetragrams, not accessible per Unicode
Hangul hngl S1,3 Transliterates Chinese-style characters with Korean Hangul
Leading Jamo Forms ljmo S4 Initial group of consonants for a synthesized Korean Hangul tetragram
Trailing Jamo Forms tjmo S4 Final group of consonants for a synthesized Korean Hangul tetragram
Vowel Jamo Forms vjmo S4 Medial group of vowels for a synthesized Korean Hangul tetragram
Full Widths fwid S1 Substitutes proportionally spaced character with full-width versions (esp. for Latin letters within Chinese)
Half Widths hwid S1,P1 Substitutes uniformly-spaced characters with half-width version
Alternate Half Widths halt P1 Re-positions full-width glyphs on half-width spaces
Third Widths twid S1,P1 Substitutes uniformly-spaced character with a version of 1/3 width (punctuation, etc.)
Quarter Widths qwid S1 Replaces uniformly-spaced glyphs with quarter-width ones (punctuation etc.)
Proportional Widths pwid S1 Replaces uniformly-spaced glyphs with proportional ones
Proportional Alternates palt P1 Re-positions otherwise monospace characters according to glyph width
Proportional Kana pkna S1 Kana for use alongside alphabets, without grid typography
Ruby Notation Forms ruby S1 Ruby characters, small print
Horizontal Kana Alternates hkna S1 Alternate forms for horizontal kana text, e.g. ー for chōonpu instead of ｜, cf. vkna
Vertical Kana vkna S1 Alternate Japanese kana forms for vertical text, e.g. ｜ for chōonpu instead of ー, cf. hkna
Centered CJK Punctuation cpct P1 Positions punctuation marks vertically and horizontally

Features primarily intended for or exclusively required by West-Asian (Semitic, Arabic) and other cursive scripts or fonts

Long name tag type Description
Cursive Positioning curs P3 Precise positioning of a letter's connection to an adjacent one
Justification Alternates jalt S3 User selectable wider and narrower alternates, used especially for justifying
Mark Positioning via Substitution mset S5 Used in Windows 95 for positioning of Arabic marks
Required Contextual Alternates rclt S6 Contextual alternates required for correct text display which differs from the default join for other letters, required especially important by Arabic
Required Ligatures rlig S3 Ligatures required for correct text display (any script, but in cursive)
Isolated Forms isol S1 Substitutes a special form of a letter occurring outside a word (required by Arabic and Syriac)
Initial Forms init S1 Substitutes a special form of a letter occurring at the beginning of a word (required by Arabic and Syriac)
Medial Forms medi S1 Substitutes a special form of letters between other letters in words (required by Arabic and Syriac)
Medial Form #2 med2 S5 Syriac
Terminal Forms fina S1 Substitutes a special form of a letter at end of words (required by Arabic and Syriac)
Terminal Form #2 fin2 S5 Syriac
Terminal Form #3 fin3 S5 Syriac
Final Glyph on Line Alternates falt S3 Replaces final glyph on the line with an alternate
Stretching Glyph Decomposition stch S2 Substitutes a special form of a stretchy glyph onto one or more letters (required by Syriac)

Features intended for bicameral [cased] alphabets (Latin, Greek, Cyrillic, etc.)

Long name tag type Description
Small Caps smcp S1 Substitutes lower-case letters with small caps versions
Capitals to Small Caps c2sc S1 Substitutes capital letters with small caps
Petite Caps pcap S1 Substitute lower-case letters with their petite caps analogs
Capitals to Petite Caps c2pc S1 Substitutes capital letters with petite caps
Unicase unic S1 Replaces lowercase and uppercase letters with a set of single case glyphs
Capital Spacing cpsp P1 Adjusts spacing between letters in all-capitals text
Case Sensitive Forms case P1 Replace characters, especially punctuation, with forms better suited for all-capital text, cf. titl
Italics ital S1 Replaces letter with corresponding italic glyph
Ordinals ordn S6,4 Replaces characters with ordinal forms for use after numbers

Features depending on writing direction

Long name tag type Description
Alternative Vertical Metrics valt P1 Positions shorter characters to be centered vertically with full-height characters
Alternative Vertical Half Metrics vhal P1 Positions characters to be centered vertically with half-height characters
Proportional Alternate Vertical Metrics vpal P1 Re-positions glyphs vertically to be centered on proportional full-height characters
Vertical Alternates vert S1 A subset of vrt2: prefer the latter feature
Vertical Alternates and Rotation vrt2 S1 Replaces characters with forms suitable for vertical writing, possibly by rotating 90°
Vertical Alternates for Rotation vrtr S1 Replaces characters with forms suitable for vertical writing, possibly by shifting or shape
Vertical Kerning vkrn P2,8 Fine vertical positioning of characters based on shape
Left-to-right glyph alternates ltra S1 Replaces characters with forms befitting left-to-right presentation (except mirrored forms)
Left-to-right mirrored forms ltrm S1 Replaces characters with possibly mirrored forms befitting left-to-right presentation
Right-to-left glyph alternates rtla S1 Replaces characters with forms befitting right-to-left presentation (except mirrored forms)
Right-to-left mirrored forms rtlm S1 Replaces characters with possibly mirrored forms befitting right-to-left presentation

Features intended for digits and math

Long name tag type Description
Lining Figures lnum S1 Replaces numerals with glyphs meant to fit better in all-capitals text, often also tnum
Oldstyle Figures onum S1 Replaces numerals with cased old-style numerals, often also pnum
Proportional Figures pnum S1 Replaces numerals with glyphs of proportional width, often also onum
Tabular Figures tnum S1 Replaces numerals with glyphs of uniform width, often also lnum
Fractions frac S4 Converts figures separated by slash with diagonal fraction
Alternative Fractions afrc S4 Converts figures separated by slash with alternative stacked fraction form
Denominator dnom S1 Converts to appropriate fraction denominator form, invoked by frac
Numerator numr S1 Converts to appropriate fraction numerator form, invoked by frac
Scientific Inferiors sinf S1 as in "H2O", "SOx" or "YCbCr" (but using the same font weight and predefined position in contrast these plain HTML subs and sups)
Slashed Zero zero S1 Replaces 0 figure with slashed 0
Mathematical Greek mgrk S1 Replaces Greek characters with special forms for use in mathematics
Flattened accent forms flac This feature is applied to individual glyphs during layout of math formula.
Dotless Forms dtls The dotless forms are to be used as base forms for placing mathematical accents over them.
Math script style alternates ssty This feature can have a parameter indicating the script level: 1 for simple subscripts and superscripts, 2 for second level subscripts and superscripts (that is, scripts on scripts), and so on. (Currently, only the first two alternates are used). For glyphs that are not covered by this feature, the original glyph is used in subscripts and superscripts.

Ligation and alternate forms features intended for all scripts

Long name tag type Description
Access All Alternates aalt S1,3 Special feature: used to present user with choice all alternate forms of the character
Swash swsh S1,3 Either replaces character with or displays multiple swashed versions
Contextual Swash cswh S8 Converts letter to a swashed version based on characters around the letter
Contextual Alternates calt S6 Applies a second substitution feature based on a match of a character pattern within a context of surrounding patterns
Historical Forms hist S1 Obsolete forms of characters to be applied at the user's discretion, cf. hlig
Localized Forms locl S1 Substitutes character with the preferred form based on script language
Randomize rand S3 Replaces character with random forms (meant to simulate handwriting)
Alternate Annotation Forms nalt S1,3 Provides user access to circled digits, inverse letters etc.
Character Variant 1–99 cv01–
cv99		 S3 Multiple variants of a single character, which may not apply to many other characters, see references for voluminous documentation
Stylistic Alternates salt S1,3 Either replaces with, or displays list of, stylistic alternatives for a character
Stylistic Set 1 – 20 ss01-
ss20		 S1 Replaces character with one from a font-specific set of stylistic alternatives
Subscript subs S1 Replaces character with subscript version, cf. numr
Superscript sups S1 Replaces character with superscript version, cf. dnom
Titling Alternates titl S1 Replaces characters with forms suited for large type, as in titles
Required Variation Alternates rvrn S1 Special variants of a single character, which need apply to specific font variation, required by variable fonts
Contextual Ligatures clig S8 Applies a second ligature feature based on a match of a character pattern within a context of surrounding patterns
Discretionary Ligatures dlig S4 Ligatures to be applied at the user's discretion
Historical Ligatures hlig S1 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 •

Legend of substitution and positioning codes

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.

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:

  • Annotation nalt
    • No Annotation
    • Box Annotation
    • Rounded Box Annotation
    • Circle Annotation
    • Inverted Circle Annotation
    • Parenthesis Annotation
    • Period Annotation
    • Roman Numeral Annotation
    • Diamond Annotation
  • Character Alternatives
    • No Alternates
    • … rand; aalt, calt, falt, jalt, salt, ssXX, hkna/vkna, rtla, vrt2
  • Character Shape half, ruby; ljmo, vjmo, tjmo
    • Traditional Characters trad
    • Simplified Characters smpl
    • JIS 1978 Characters jp78
    • JIS 1983 Characters jp83
    • JIS 1990 Characters jp90
    • Traditional Characters, Alternative Set 1…5 tnam, hojo, nlck
    • Expert Characters expt, locl
  • CJK Latin Spacing
    • Half-width hwid, halt
    • Proportional pwid, palt
    • Default Latin
    • Full-width Latin fwid
  • Cursive Connection init, medi/med2, fina/fin2/fin3; haln, nukt, vatu, rphf, pres, pstf/psts
    • Unconnected isol
    • Partially Connected calt, clig
    • Cursive curs
  • Design Complexity
    • Design Level 1
    • Design Level …
  • Diacritics
    • Show Diacritics
    • Hide Diacritics
    • Decompose Diacritics ccmp
  • Fractions
    • No Fractions
    • Vertical Fractions afrc
    • Diagonal Fractions frac, dnom, numr
  • Ideographic Spacing
    • Full Width fwid
    • Proportional pwid, palt
  • Kana Spacing
    • Full Width fwid
    • Proportional pwid, palt
  • Letter Case case
    • Upper & Lower Case
    • All Caps
    • All Lower Case
    • Small Caps smcp, pcap
    • Initial Caps c2sc, c2pc
    • Initial Caps and Small Caps
  • Number Case
    • Lower Case Numbers onum
    • Upper Case Numbers lnum
  • Number Spacing
    • Monospaced Numbers tnum
    • Proportional Numbers pnum
  • Ornament Sets ornm
    • None
    • Dingbats
    • Pi Characters
    • Fleurons
    • Decorative Borders
    • International Symbols
    • Math Symbols mgrk
  • Text Spacing
    • Proportional pwid, palt
    • Monospace fwid
    • Half-width hwid, halt
    • Normal
  • Vertical Position
    • No Vertical Position
    • Superiors supr
    • Inferiors subs, sinf
    • Ordinals ordn

Features that take a number of values:

  • Ligatures
    • Required Ligatures rlig, clig
    • Common Ligatures liga
    • Rare Ligatures hlig, dlig
    • Logos
    • Rebus Pictures
    • Diphthong Ligatures
    • Squared Ligatures
    • Squared Ligatures, Abbreviated
  • Mathematical Extras
    • Hyphen to Minus (‘-’ → ‘−’)
    • Asterisk to Multiply (‘*’ → ‘×’)
    • Slash to Divide (‘/’ → ‘÷’)
    • Inequality Ligatures
    • Exponents
  • Smart Swashes swsh, cswh
    • Word Initial Swashes
    • Word Final Swashes
    • Line Initial Swashes
    • Line Final Swashes falt
    • Non-Final Swashes jalt
  • Style Options
    • No Style Options
    • Display Text size
    • Engraved Text
    • Illuminated Caps
    • Titling Caps titl
    • Tall Caps
  • Transliteration locl
  • Typographic Extras
    • Hyphens to Em Dash (‘--’ → ‘—’)
    • Hyphen to En Dash (‘-’ → ‘–’)
    • Unslashed Zero zero
    • Form Interrobang (‘!?’/‘?!’ → ‘‽’)
    • Smart Quotes (‘"'"’ → ‘“’”’)
    • Periods to Ellipsis (‘...’ → ‘…’)

Binary features that can only be turned on:

  • All Typographic Features
  • Linguistic Rearrangement
  • Overlapping Characters
  • Vertical Substitution

External links

  • "Layout tag registry", OpenType spec, Microsoft, 9 December 2021
  • "Font Feature Registry", Fonts, Apple – AAT layout tag specs
  • OpenType User Guide for Adobe Fonts (PDF), Adobe
  • An Introduction to OpenType Substitution Features, I love typography
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