@font-face {
    font-family: "AccuroVar";
    src: url("accurovar.otf") format("opentype");
    font-named-instance: "Grotesque";
    font-variation-settings: "XHGT" 0.7;
}

Font request guidelines

Font loading guidelines

@font-face {
  font-family: GeometricModern;
  src: url(font.woff);
}

p {
  /* font will be downloaded for pages with p elements */
  font-family: GeometricModern, sans-serif;
}

h2 {
  /* font may be downloaded for pages with h2 elements, even if Futura is available locally */
  font-family: Futura, GeometricModern, sans-serif;
}

Font fetching requirements

/* same origin (i.e. domain, scheme, port match document) */
src: url(fonts/simple.woff);

/* data urls with no redirects are treated as same origin */
src: url("data:application/font-woff;base64,...");

/* cross origin, different domain */
/* Access-Control-Allow-Origin response header set to '*' */
src: url(http://another.example.com/fonts/simple.woff);

/* cross origin, different scheme */
/* no Access-Control-xxx headers in response */
src: url(http://example.com/fonts/simple.woff);

/* cross origin, different domain */
/* no Access-Control-xxx headers in response */
src: url(http://another.example.com/fonts/simple.woff);

Controlling Font Display Per Font-Face: the 'font-display!!descriptor' descriptor

Name: font-display
Value: auto | block | swap | fallback | optional
Initial: auto
For: @font-face

auto

The font display policy is user-agent-defined. Note: Many browsers have a default policy similar to that specified by ''display/block''.

block

Gives the font face a short block period (''3s'' is recommended in most cases) and an infinite swap period. Note: In other words, the browser draws "invisible" text at first if it's not loaded, but swaps the font face in as soon as it loads. This value must only be used when rendering text in a particular font is required for the page to be usable. It must only be used for small pieces of text.

For example, badly designed "icon fonts" might associate a "⎙" (printer) icon with an unrelated character like "P", so if the text is displayed with a fallback font instead there will be confusing letters scattered around the page rather than the desired icon. In this case, temporary blank spots are better than using a fallback font. (However, the fallback font is used eventually, as having confusing letters scattered around the page is better than having links and such never show up at all.) A better solution is described in the Accessibility Considerations section.

swap

Gives the font face an extremely small block period (''100ms'' or less is recommended in most cases) and an infinite swap period. Note: In other words, the browser draws the text immediately with a fallback if the font face isn't loaded, but swaps the font face in as soon as it loads. This value should only be used when rendering text in a particular font is very important for the page, but rendering in any font will still get a correct message across. It should only be used for small pieces of text.

For example, if a website has a custom font for rendering their logo, rendering that logo correctly is fairly important for branding purposes, but displaying the logo in any font will at least get the point across without confusion.

fallback

Gives the font face an extremely small block period (''100ms'' or less is recommended in most cases) and a short swap period (''3s'' is recommended in most cases). Note: In other words, the font face is rendered with a fallback at first if it's not loaded, but it's swapped in as soon as it loads. However, if too much time passes, the fallback will be used for the rest of the page's lifetime instead. This value should be used for body text, or any other text where the use of the chosen font is useful and desired, but it's acceptable for the user to see the text in a fallback font. This value is appropriate to use for large pieces of text.

For example, in large pieces of body text, it's most important just to get the text rendered quickly, so the user can begin to read as quickly as possible. Further, once the user has started reading, they shouldn't be disturbed by the text suddenly "shifting" as a new font is swapped in, as that's distracting and annoying to re-find where one was in the text.

optional

If the font can be loaded "immediately" (such that it's available to be used for the "first paint" of the text), the font is used. Otherwise, the font is treated as if its [=block period=] and [=swap period=] both expired before it finished loading. If the font is not used due to this, the user agent may choose to abort the font download, or download it with a very low priority. If the user agent believes it would be useful for the user, it may avoid even starting the font download, and proceed immediately to using a fallback font. An ''optional'' font must never cause the layout of the page to "jump" as it loads in. A user agent may choose to slightly delay rendering an element using an optional font to give it time to load from a possibly-slow local cache, but once the text has been painted to the screen with a fallback font instead, it must not be rendered with the ''optional'' font for the rest of the page's lifetime. This value should be used for body text, or any other text where the chosen font is purely a decorative "nice-to-have". It should be used anytime it is more important that the web page render quickly on first visit, than it is that the user wait a longer time to see everything perfect immediately.

For example, body text is perfectly readable in one of the browser default fonts, though a downloadable font face might be more attractive and mesh with the site's aesthetics better. First time visitors to a site generally care far more about the site being quickly usable than they do about the finer points of its display, and ''optional'' provides a good behavior for them. If they return later, the desired font faces might have finished downloading, giving them the "intended" experience without slowing down either their first or subsequent visits. Users on very slow connections might not ever receive the "intended" experience, but ''optional'' ensures they can actually use the site, rather than quitting and going elsewhere because the site takes too long to load.

To increase the chance that an ''optional'' font will be available in time to use for rendering some text, it is recommended that the user agent employ heuristics to make it faster to access or to judge when it would be worthwhile to delay rendering some text, such as checking if the font is preloaded in HTML, or moving the file from slower to faster in-memory caches as soon as it is seen in a stylesheet (before it's known whether it will be used on the page). These heuristics cannot be relied upon by authors, however; it must be understood that the ''optional'' value can result in the font never being used. If a somewhat higher assurance of the font being used is needed, authors should consider using the ''fallback'' value.

Controlling Font Display Per Font-Family via ''@font-feature-values''

Name: font-display
Value: auto | block | swap | fallback | optional
Initial: auto
For: @font-feature-values

Default font language overriding: the 'font-language-override' descriptor

Name: font-language-override
Value: normal | <>
For: @font-face
Initial: normal

Default font metrics overriding: the 'ascent-override!!descriptor', 'descent-override!!descriptor' and 'line-gap-override!!descriptor' descriptors

Name: ascent-override
Value: normal | <>
For: @font-face
Initial: normal

Name: descent-override
Value: normal | <>
For: @font-face
Initial: normal

Name: line-gap-override
Value: normal | <>
For: @font-face
Initial: normal

@font-face {
  font-family: overridden-font;
  ascent-override: 50%;
  ...
}

<span style="font-family: overridden-font; font-size: 20px;">
  Outer span content
  <span style="font-size: 150%;">Inner span content</span>
</span>

@font-face {
  font-family: cool-web-font;
  src: url("https://example.com/font.woff");
}

@font-face {
  font-family: fallback-to-local;
  src: local(Some Local Font);
  /* Override metric values to match cool-web-font */
  ascent-override: 125%;
  descent-override: 25%;
  line-gap-override: 0%;
}

<div style="font-family: cool-web-font, fallback-to-local">Title goes here</div>
<img src="https://example.com/largeimage" alt="A large image that you don't want to shift">

Font Matching Algorithm

Localized name matching

For example, for each of the fonts listed below, the author can use either the Latin name or the localized name in the 'font-family!!property' property, and the results will be identical on all systems:

Matching font styles

1. Using the computed font property values for a given element, the user agent starts with the first family name specified by the 'font-family!!property' property. 2. If the family name is a generic family keyword, the user agent looks up the appropriate font family name to be used. User agents may choose the generic font family to use based on the language of the containing element or the Unicode range of the character. 3. For other family names, the user agent attempts to find the family name among fonts defined via ''@font-face'' rules and then among available installed fonts (this may include font aliases), matching names with a [[#localized-name-matching]] as outlined in the section above. If the font resources defined for a given face in an ''@font-face'' rule are either not available or contain invalid font data, then the face should be treated as not present in the family. If no faces are present for a family defined via ''@font-face'' rules, the family should be treated as missing; matching a platform font with the same name must not occur in this case. 4. If a font family match occurs, the user agent assembles the set of font faces in that family and then narrows the set to a single face using other font properties in the order given below. Fonts might be present in this group which can support a range of 'font-stretch!!property', 'font-style!!property', or 'font-weight!!property' properties. In this case, the algorithm proceeds as if each supported combination of values is a unique font in the set. If such a font is ultimately selected by this algorithm, particular values for 'font-stretch!!property', 'font-style!!property', and 'font-weight!!property' must be applied before any layout or rendering occurs. The application of these values must be applied in the Apply font matching variations step detailed in [[#font-feature-variation-resolution]]. A group of faces defined via ''@font-face'' rules with identical font descriptor values but differing 'unicode-range!!descriptor' values are considered to be a single composite face for this step: matching/fixed-stretch-style-over-weight.html matching/stretch-distance-over-weight-distance.html matching/style-ranges-over-weight-direction.html
1. 'font-stretch!!property' is tried first. If a font does not have any concept of varying strengths of stretch values, its stretch value is mapped according table in the property definition. If the matching set includes faces with width values containing the 'font-stretch!!property' desired value, faces with width values which do not include the desired width value are removed from the matching set. If there is no face which contains the desired value, a stretch value is chosen using the rules below: * If the desired stretch value is less than or equal to 100%, stretch values below the desired stretch value are checked in descending order followed by stretch values above the desired stretch value in ascending order until a match is found. * Otherwise, stretch values above the desired stretch value are checked in ascending order followed by stretch values below the desired stretch value in descending order until a match is found. Once the closest matching width has been determined by this process, faces with widths which do not include this determined width are removed from the matching set.
This search algorithm can be thought of as a distance function, where the lowest-distance value present in the font family is selected, and all fonts not including that value are eliminated. Consider a font family with three fonts, named A, B, and C, each with associated supported ranges for the 'font-stretch!!property' descriptor. If an element is styled with "font-stretch: 125%", the search algorithm can be visualized as follows: The font stretch ranges supported by fonts A, B, and C are shown in the graph above. As you can see, because font B contains the minimum stretch value across the entire family, font B would be selected by this algorithm. However, if font B were somehow eliminated from the family, font C would then contain the lowest distance in the family, so it would be selected.
Similar to the previous example, here is the conceptual distance graph for an element styled with "font-stretch: 75%": As you can see, because font B contains the minimum stretch value across the entire family, font B would be selected by this algorithm. However, if font B were somehow eliminated from the family, font A would then contain the lowest distance in the family, so it would be selected.
2. 'font-style!!property' is tried next (see [[#font-style-matching]]). If a font does not have any concept of varying strengths of italics or oblique angles, its style is mapped according to the description in the 'font-style!!property' property definition. If the value of 'font-style!!property' is ''italic'': 1. If the matching set includes faces with italic values containing the mapped value of ''italic'', then faces with italic values which do not include the desired italic mapped value are removed from the matching set. 2. Otherwise, italic values above the desired italic value are checked in ascending order followed by italic values below the desired italic value, until 0 is hit. Only positive values of italic values are checked in this stage. 3. If no match is found, oblique values greater than or equal to 11deg are checked in ascending order followed by oblique values below 11deg in descending order, until 0 is hit. Only positive values of oblique values are checked in this stage. ISSUE: The threshold for preferring oblique over normal should be lower than the average angle. 4. If no match is found, italic values less than or equal to 0 are checked in descending order until a match is found. 5. If no match is found, oblique values less than or equal to 0deg are checked in descending order until a match is found.
Similar to the previous example, here is the conceptual distance graph for an element styled with "font-style: italic": As you can see, because font D contains the minimum italic value across the entire family, font D would be selected by this algorithm. However, if font D were somehow eliminated from the family, font E would then contain the lowest distance in the family, so it would be selected. If E were eliminated, C would be selected. If C were eliminated, font B would not be chosen immediately; instead, oblique values would be consulted and an oblique value might be chosen. However, if no oblique value is chosen, font B would then be selected, followed by font A.
If the value of 'font-style!!property' is ''oblique'' and the requested angle is greater than or equal to 11deg,
1. If the matching set includes faces with oblique values containing the value of ''oblique'', faces with oblique values which do not include the desired oblique value are removed from the matching set. 2. Otherwise, oblique values above the desired oblique value are checked in ascending order followed by oblique values below the desired oblique value, until 0 is hit. Only positive values of oblique values are checked in this stage. 3. If 'font-synthesis-style' has the value 'font-synthesis-style/auto', then for variable fonts with a slnt axis a match is created by setting the slnt value with the specified oblique value; otherwise, a fallback match is produced by geometric shearing to the specified oblique value. 4. If no match is found, italic values greater than or equal to 1 are checked in ascending order followed by italic values below 1 in descending order, until 0 is hit. Only positive values of italic values are checked in this stage. 5. If no match is found, oblique values less than or equal to 0deg are checked in descending order until a match is found. 6. If no match is found, italic values less than or equal to 0 are checked in descending order until a match is found.
Similar to the previous example, here is the conceptual distance graph for an element styled with "font-style: oblique 40deg": As you can see, because font D contains the minimum oblique value across the entire family, font D would be selected by this algorithm. However, if font D were somehow eliminated from the family, font E would then contain the lowest distance in the family, so it would be selected. If E were eliminated, C would be selected. If C were eliminated, font B would not be chosen immediately; instead, italic values would be consulted and an italic value might be chosen. However, if no italic value is chosen, font B would then be selected, followed by font A.
If the value of 'font-style!!property' is ''oblique'' and the requested angle is greater than or equal to 0deg and less than 11deg,
1. If the matching set includes faces with oblique values containing the value of ''oblique'', faces with oblique values which do not include the desired oblique value are removed from the matching set. 2. Otherwise, oblique values below the desired oblique value are checked in descending order until 0 is hit, followed by oblique values above the desired oblique value. Only positive values of oblique values are checked in this stage. 3. If 'font-synthesis-style' has the value 'font-synthesis-style/auto', then for variable fonts with a slnt axis a match is created by setting the slnt value with the specified oblique value; otherwise, a fallback match is produced by geometric shearing to the specified oblique value. 4. If no match is found, italic values less than 1 are checked in descending order until 0 is hit, followed by italic values above 1 in ascending order. Only positive values of italic values are checked in this stage. 5. If no match is found, oblique values less than or equal to 0deg are checked in descending order until a match is found. 6. If no match is found, italic values less than or equal to 0 are checked in descending order until a match is found.
Similar to the previous example, here is the conceptual distance graph for an element styled with "font-style: oblique 13deg": As you can see, because font D contains the minimum oblique value across the entire family, font D would be selected by this algorithm. However, if font D were somehow eliminated from the family, font C would then contain the lowest distance in the family, so it would be selected. If C were eliminated, E would be selected. If E were eliminated, font B would not be chosen immediately; instead, italic values would be consulted and an italic value might be chosen. However, if no italic value is chosen, font B would then be selected, followed by font A.
If the value of 'font-style!!property' is ''oblique'' and the requested angle is less than 0deg and greater than -11deg, follow the steps above, except with the negated values and opposite directions. If the value of 'font-style!!property' is ''oblique'' and the requested angle is less than or equal to -11deg, follow the steps above, except with the negated values and opposite directions. If the value of 'font-style!!property' is ''font-style/normal'', 1. Oblique values greater than or equal to 0 are checked in ascending order. 2. If no match is found, italic values greater than or equal to 0 are checked in ascending 3. If no match is found, oblique values less than 0deg are checked in descending order until a match is found. 4. If no match is found, italic values less than 0 are checked in descending order until a match is found.
Similar to the previous example, here is the conceptual distance graph for an element styled with "font-style: normal": As you can see, because font C contains the minimum oblique value across the entire family, font C would be selected by this algorithm. However, if font C were somehow eliminated from the family, font B would not be chosen immediately; instead, italic values would be consulted and an italic value might be chosen. However, if no italic value is chosen, font B would then be selected, followed by font A.
If an oblique angle was found in the above search, all faces which don't include that oblique angle are excluded from the matching set. Otherwise, if an italic value was found in the above search, all faces which don't include that italic value are excluded from the matching set. User agents are not required to distinguish between italic and oblique fonts. In such user agents, the 'font-style!!property' matching steps above are performed by mapping both italic values and oblique angles onto a common scale. The exact nature of this mapping is undefined, however, an italic value of 1 must map to the same value that an oblique angle of 11deg maps to. Within font families defined via ''@font-face'' rules, italic and oblique faces must be distinguished using the value of the 'font-style!!descriptor' descriptor. For families that lack any italic or oblique faces, user agents may create artificial oblique faces, if this is permitted by the value of the 'font-synthesis' property. 3. 'font-weight!!property' is matched next. If a font does not have any concept of varying strengths of weights, its weight is mapped according list in the property definition. If bolder/lighter relative weights are used, the effective weight is calculated based on the inherited weight value, as described in the definition of the 'font-weight!!property' property. If the matching set after performing the steps above includes faces with weight values containing the font-weight desired value, faces with weight values which do not include the desired font-weight value are removed from the matching set. If there is no face which contains the desired value, a weight value is chosen using the rules below: * If the desired weight is inclusively between 400 and 500, weights greater than or equal to the target weight are checked in ascending order until 500 is hit and checked, followed by weights less than the target weight in descending order, followed by weights greater than 500, until a match is found. * If the desired weight is less than 400, weights less than or equal to the desired weight are checked in descending order followed by weights above the desired weight in ascending order until a match is found. * If the desired weight is greater than 500, weights greater than or equal to the desired weight are checked in ascending order followed by weights below the desired weight in descending order until a match is found.
Similar to the previous example, here is the conceptual distance graph for an element styled with "font-weight: 400": As you can see, because font B contains the minimum distance across the entire family, font B would be selected by this algorithm. However, if font B were somehow eliminated from the family, font C would then contain the lowest distance in the family, so it would be selected. If C were eliminated, D would be selected, followed by fonts A and then E.
Similar to the previous example, here is the conceptual distance graph for an element styled with "font-weight: 450": As you can see, because font C contains the minimum distance across the entire family, font C would be selected by this algorithm. However, if font C were somehow eliminated from the family, font D would then contain the lowest distance in the family, so it would be selected. If D were also eliminated, B would be selected, followed by fonts A and then E.
Similar to the previous example, here is the conceptual distance graph for an element styled with "font-weight: 500": As you can see, because font D contains the minimum distance across the entire family, font D would be selected by this algorithm. However, if font D were somehow eliminated from the family, font B would then contain the lowest distance in the family, so it would be selected. If B were eliminated, C would be selected, followed by fonts B, A, and then E.
Similar to the previous example, here is the conceptual distance graph for an element styled with "font-weight: 300": As you can see, because font B contains the minimum distance across the entire family, font B would be selected by this algorithm. However, if font B were somehow eliminated from the family, font A would then contain the lowest distance in the family, so it would be selected. If A were eliminated, C would be selected.
Once the closest matching weight has been determined by this process, faces with weights which do not include this determined weight are removed from the matching set. Note: There is a small behavior change between [[CSS-FONTS-3]] and this specification with the animation of the 'font-weight!!property' property. Previously, interpolated values of font-weight were rounded to their closest multiple of 100, and the font-matching algorithm was run on these rounded values. In this specification, the font-matching algorithm is able to accept any value, so no rounding occurs. The small behavior change is due to the discontinuous nature of the font-matching algorithm. 4. 'font-size' must be matched within a UA-dependent margin of tolerance. (Typically, sizes for scalable fonts are rounded to the nearest whole pixel, while the tolerance for bitmapped fonts could be as large as 20%.) Further computations, e.g., by ''em'' values in other properties, are based on the 'font-size' value that is used, not the one that is specified.
Note that more than one font might be remaining in the matching set after performing the above steps. If so, the user agent must choose a single font from the matching set and continue these steps with it. The choice of which font to choose can differ between multiple user agents and multiple operating system platforms; however, it must not differ between two elements in the same document. 5. If the matched face is defined via ''@font-face'' rules, user agents must use the procedure below to select a single font: 1. If the font resource has not been loaded and the range of characters defined by the 'unicode-range!!descriptor' descriptor value includes the character in question, load the font. 2. After downloading, if the effective character map supports the character in question, select that font. When the matched face is a composite face, user agents must use the procedure above on each of the faces in the composite face in reverse order of ''@font-face'' rule definition. While the download occurs, user agents must either wait until the font is downloaded or render once with substituted font metrics and render again once the font is downloaded. 6. If no matching face exists or the matched face does not contain a glyph for the character to be rendered, the next family name is selected and the previous three steps repeated. Glyphs from other faces in the family are not considered. The only exception is that user agents may optionally substitute a synthetically obliqued version of the default face if that face supports a given glyph and synthesis of these faces is permitted by the value of the 'font-synthesis' property. For example, a synthetic italic version of the regular face might be used if the italic face doesn't support glyphs for Arabic. 7. If there are no more font families to be evaluated and no matching face has been found, then the user agent performs an installed font fallback procedure to find the best match for the character to be rendered. The result of this procedure can vary across user agents. 8. If a particular character cannot be displayed using any font, the user agent should indicate by some means that a character is not being displayed, displaying either a symbolic representation of the missing glyph (e.g. using a Last Resort Font) or using the missing character glyph from a default font.

Cluster matching

1. For each family in the font list, a face is chosen using the style selection rules defined in the previous section.
   1. If all characters in the sequence b + c1 + c2 … are completely supported by the font, select this font for the sequence.
   2. If a sequence of multiple codepoints is canonically equivalent to a single character and the font supports that character, select this font for the sequence and use the glyph associated with the canonically equivalent character for the entire cluster.
2. If no font was found in the font list in step 1:
   1. If c1 is a variation selector, system fallback must be used to find a font that supports the full sequence of b + c1. If no font on the system supports the full sequence, match the single character b using the normal procedure for matching single characters and ignore the variation selector. Note: a sequence with more than one variation selector must be treated as an encoding error and the trailing selectors must be ignored. [[!UNICODE]]
   2. Otherwise, the user agent may optionally use installed font fallback to match a font that supports the entire cluster.
3. If no font is found in step 2, use the matching sequence from step 1 to determine the longest sequence that is completely supported by a font in the font list and attempt to match the remaining combining characters separately using the rules for single characters.

Character handling issues

Font Feature Properties

Glyph selection and positioning

Language-specific display

Kerning: the 'font-kerning' property

Name: font-kerning

Value: auto | normal | none
Initial: auto
Applies to: all elements and text
Inherited: yes
Percentages: n/a
Computed value: as specified
Animation type: discrete

Kerning is the contextual adjustment of inter-glyph spacing. This property controls metric kerning, kerning that utilizes adjustment data contained in the font.

auto

Specifies that kerning is applied at the discretion of the user agent

normal

Specifies that kerning is applied

none

Specifies that kerning is not applied

For fonts that do not include kerning data this property will have no visible effect. When rendering with OpenType fonts, the [[!OPENTYPE]] specification suggests that kerning be enabled by default. When kerning is enabled, the relevant OpenType kerning features are enabled (for horizontal [=typographic modes=] and for [=sideways typesetting=] in vertical [=typographic modes=], the kern feature; for [=upright typesetting=] in [=vertical typographic modes=], the vkrn feature. User agents must also support fonts that only support kerning via data contained in a kern font table, as detailed in the OpenType specification. If the 'letter-spacing' property is defined, kerning adjustments are considered part of the default spacing and letter spacing adjustments are made after kerning has been applied.

When set to 'auto', user agents can determine whether to apply kerning or not based on a number of factors: text size, script, or other factors that influence text processing speed. Authors who want proper kerning should use 'normal' to explicitly enable kerning. Likewise, some authors may prefer to disable kerning in situations where performance is more important than precise appearance. However, in well-designed modern implementations the use of kerning generally does not have a large impact on text rendering speed.

Ligatures: the 'font-variant-ligatures' property

Name: font-variant-ligatures

Value: normal | none | [ <common-lig-values> || <discretionary-lig-values> || <historical-lig-values> || <contextual-alt-values> ]
Initial: normal
Applies to: all elements and text
Inherited: yes
Percentages: n/a
Computed value: as specified
Animation type: discrete

Ligatures and contextual forms are ways of combining glyphs to produce more harmonized forms.

<common-lig-values>        = [ common-ligatures | no-common-ligatures ]

<discretionary-lig-values> = [ discretionary-ligatures | no-discretionary-ligatures ]

<historical-lig-values>    = [ historical-ligatures | no-historical-ligatures ]

<contextual-alt-values>    = [ contextual | no-contextual ]

Individual values have the following meanings:

normal

A value of 'normal' specifies that common default features are enabled, as described in detail in the next section. For OpenType fonts, common ligatures and contextual forms are on by default, discretionary and historical ligatures are not.

none

Specifies that all types of ligatures and contextual forms covered by this property are explicitly disabled. In situations where ligatures are not considered necessary, this may improve the speed of text rendering.

common-ligatures

Enables display of common ligatures (OpenType features: liga, clig). For OpenType fonts, common ligatures are enabled by default.

no-common-ligatures

Disables display of common ligatures (OpenType features: liga, clig).

discretionary-ligatures

Enables display of discretionary ligatures (OpenType feature: dlig). Which ligatures are discretionary or optional is decided by the type designer, so authors will need to refer to the documentation of a given font to understand which ligatures are considered discretionary.

no-discretionary-ligatures

Disables display of discretionary ligatures (OpenType feature: dlig).

historical-ligatures

Enables display of historical ligatures (OpenType feature: hlig).

no-historical-ligatures

Disables display of historical ligatures (OpenType feature: hlig).

contextual

Enables display of contextual alternates (OpenType feature: calt). Although not strictly a ligature feature, like ligatures this feature is commonly used to harmonize the shapes of glyphs with the surrounding context. For OpenType fonts, this feature is on by default.

no-contextual

Disables display of contextual alternates (OpenType feature: calt).

Required ligatures, needed for correctly rendering complex scripts, are not affected by the settings above, including 'none' (OpenType feature: rlig).

Subscript and superscript forms: the 'font-variant-position' property

Name: font-variant-position

Value: normal | sub | super
Initial: normal
Applies to: all elements and text
Inherited: yes
Percentages: n/a
Computed value: as specified
Animation type: discrete

This property is used to enable typographic subscript and superscript glyphs. These are alternate glyphs designed within the same em-box as default glyphs and are intended to be laid out on the same baseline as the default glyphs, with no resizing or repositioning of the baseline. They are explicitly designed to match the surrounding text and to be more readable without affecting the line height.

Subscript glyphs (top) vs. typical synthesized subscripts (bottom)

Individual values have the following meanings:

normal

None of the features listed below are enabled.

sub

Enables display of subscript variants (OpenType feature: subs).

super

Enables display of superscript variants (OpenType feature: sups).

Because of the semantic nature of subscripts and superscripts, when the value is either 'sub' or 'super' for a given contiguous run of text, if a variant glyph is not available for all the characters in the run, simulated glyphs should be synthesized for all characters using reduced forms of the glyphs that would be used without this feature applied. This is done per run to avoid a mixture of variant glyphs and synthesized ones that would not align correctly. In the case of OpenType fonts that lack subscript or superscript glyphs for a given character, user agents must synthesize appropriate subscript and superscript glyphs.

Superscript alternate glyph (left), synthesized superscript glyphs (middle), and incorrect mixture of the two (right)

In situations where text decorations are only applied to runs of text containing superscript or subscript glyphs, the synthesized glyphs may be used, to avoid problems with the placement of decorations.

In the past, user agents have used font-size and vertical-align to simulate subscripts and superscripts for the sub and sup elements. To allow a backwards compatible way of defining subscripts and superscripts, it is recommended that authors use conditional rules [[CSS3-CONDITIONAL]] so that older user agents will still render subscripts and superscripts via the older mechanism.

Because font-size: smaller is often used for these elements, the effective scaling factor applied to subscript and superscript text varies depending upon the size. For larger text, the font size is often reduced by a third but for smaller text sizes, the reduction can be much less. This allows subscripts and superscripts to remain readable even within elements using small text sizes. User agents should consider this when deciding how to synthesize subscript and superscript glyphs.

The OpenType font format defines subscript and superscript metrics in the OS/2 table [[!OPENTYPE]] but these are not always accurate in practice and so cannot be relied upon when synthesizing subscript and superscript glyphs.

Authors should note that fonts typically only provide subscript and superscript glyphs for a subset of all characters supported by the font. For example, while subscript and superscript glyphs are often available for Latin numbers, glyphs for punctuation and letter characters are less frequently provided. The synthetic fallback rules defined for this property try to ensure that subscripts and superscripts will always appear but the appearance may not match author expectations if the font used does not provide the appropriate alternate glyph for all characters contained in a subscript or superscript.

This property is not cumulative. Applying it to elements within a subscript or superscript won't nest the placement of a subscript or superscript glyph. Images contained within text runs where the value of this property is 'sub' or 'super' will be drawn just as they would if the value was 'normal'.

Because of these limitations, 'font-variant-position' is not recommended for use in user agent stylesheets. Authors should use it in cases where subscripts or superscripts will only contain the narrow range of characters supported by the fonts specified.

The variant glyphs use the same baseline as the default glyphs would use. There is no shift in the placement along the baseline, so the use of variant glyphs doesn't affect the height of the inline box or alter the height of the linebox. This makes superscript and subscript variants ideal for situations where it's important that leading remain constant, such as in multi-column layout.

sub {
	vertical-align: sub;
	font-size: smaller;
	line-height: normal;
}

@supports ( font-variant-position: sub ) {

	sub {
	vertical-align: baseline;
	font-size: 100%;
	line-height: inherit;
	font-variant-position: sub;
	}

}

Capitalization: the 'font-variant-caps' property

Name: font-variant-caps

Value: 	normal | small-caps | all-small-caps | petite-caps | all-petite-caps | unicase | titling-caps
Initial: normal
Applies to: all elements and text
Inherited: yes
Percentages: n/a
Computed value: as specified
Animation type: discrete

This property allows the selection of alternate glyphs used for small or petite capitals or for titling. These glyphs are specifically designed to blend well with the surrounding normal glyphs, to maintain the weight and readability which suffers when text is simply resized to fit this purpose.

Individual values have the following meanings:

normal

None of the features listed below are enabled.

small-caps

Enables display of small capitals (OpenType feature: smcp). Small-caps glyphs typically use the form of uppercase letters but are reduced to the size of lowercase letters.

all-small-caps

Enables display of small capitals for both upper and lowercase letters (OpenType features: c2sc, smcp).

petite-caps

Enables display of petite capitals (OpenType feature: pcap).

all-petite-caps

Enables display of petite capitals for both upper and lowercase letters (OpenType features: c2pc, pcap).

unicase

Enables display of mixture of small capitals for uppercase letters with normal lowercase letters (OpenType feature: unic).

titling-caps

Enables display of titling capitals (OpenType feature: titl). Uppercase letter glyphs are often designed for use with lowercase letters. When used in all uppercase titling sequences they can appear too strong. Titling capitals are designed specifically for this situation.

The availability of these glyphs is based on whether a given feature is defined or not in the feature list of the font. User agents can optionally decide this on a per-script basis but should explicitly not decide this on a per-character basis.

Some fonts may only support a subset or none of the features described for this property. For backwards compatibility with CSS 2.1, if 'small-caps' or 'all-small-caps' is specified but small-caps glyphs are not available for a given font, user agents should simulate a small-caps font, for example by taking a normal font and replacing the glyphs for lowercase letters with scaled versions of the glyphs for uppercase characters (replacing the glyphs for both upper and lowercase letters in the case of 'all-small-caps').

Synthetic vs. real small-caps

The 'font-feature-settings' property also affects the decision of whether or not to use a simulated small-caps font (unlike CSS Fonts 3).

#example1 { font-variant-caps: small-caps; }
	#example2 { font-variant-caps: small-caps; font-feature-settings: 'smcp' 0; }

To match the surrounding text, a font may provide alternate glyphs for caseless characters when these features are enabled but when a user agent simulates small capitals, it must not attempt to simulate alternates for codepoints which are considered caseless.

Caseless characters with small-caps, all-small-caps enabled

If either 'petite-caps' or 'all-petite-caps' is specified for a font that doesn't support these features, the property behaves as if 'small-caps' or 'all-small-caps', respectively, had been specified. If 'unicase' is specified for a font that doesn't support that feature, the property behaves as if 'small-caps' was applied only to lowercased uppercase letters. If 'titling-caps' is specified with a font that does not support this feature, this property has no visible effect. When simulated small capital glyphs are used, for scripts that lack uppercase and lowercase letters, 'small-caps', 'all-small-caps', 'petite-caps', 'all-petite-caps' and 'unicase' have no visible effect.

When casing transforms are used to simulate small capitals, the casing transformations must match those used for the 'text-transform' property.

As a last resort, unscaled uppercase letter glyphs in a normal font may replace glyphs in a small-caps font so that the text appears in all uppercase letters.

Using small capitals to improve readability in acronym-laden text

blockquote            { font-style: italic; }
blockquote:first-line { font-variant: small-caps; }

<blockquote>I'll be honor-bound to slap them like a haddock.</blockquote>

Numerical formatting: the 'font-variant-numeric' property

Name: font-variant-numeric

Value: 	normal | [ <> || <> || <> || ordinal || slashed-zero ]
Initial: normal
Applies to: all elements and text
Inherited: yes
Percentages: n/a
Computed value: as specified
Animation type: discrete

Specifies control over numerical forms. The example below shows how some of these values can be combined to influence the rendering of tabular data with fonts that support these features. Within normal paragraph text, proportional numbers are used while tabular numbers are used so that columns of numbers line up properly:

Using number styles

Possible combinations:

<numeric-figure-values>   = [ lining-nums | oldstyle-nums ]

<numeric-spacing-values>  = [ proportional-nums | tabular-nums ]

<numeric-fraction-values> = [ diagonal-fractions | stacked-fractions ]

Individual values have the following meanings:

normal

None of the features listed below are enabled.

lining-nums

Enables display of lining numerals (OpenType feature: lnum).

oldstyle-nums

Enables display of old-style numerals (OpenType feature: onum).

proportional-nums

Enables display of proportional numerals (OpenType feature: pnum).

tabular-nums

Enables display of tabular numerals (OpenType feature: tnum).

diagonal-fractions

Enables display of lining diagonal fractions (OpenType feature: frac).

stacked-fractions

Enables display of lining stacked fractions (OpenType feature: afrc).

ordinal

Enables display of letter forms used with ordinal numbers (OpenType feature: ordn).

slashed-zero

Enables display of slashed zeros (OpenType feature: zero).

sup { font-variant-position: super; }
x<sup>2</sup>

.ordinal { font-variant-numeric: ordinal; }
<span class="ordinal">17th</span>

.amount { font-variant-numeric: oldstyle-nums diagonal-fractions; }

<h4>Steak marinade:</h4>
<ul>
	<li><span class="amount">2</span> tbsp olive oil</li>
	<li><span class="amount">1</span> tbsp lemon juice</li>
	<li><span class="amount">1</span> tbsp soy sauce</li>
	<li><span class="amount">1 1/2</span> tbsp dry minced onion</li>
	<li><span class="amount">2 1/2</span> tsp italian seasoning</li>
	<li>Salt &amp; pepper</li>
</ul>

<p>Mix the meat with the marinade
and let it sit covered in the refrigerator
for a few hours or overnight.</p>

Alternates and swashes: the 'font-variant-alternates' property

Name: font-variant-alternates

Value: normal | [ stylistic(<>) ||
                  historical-forms ||
                  styleset(<>#) ||
                  character-variant(<>#) ||
                  swash(<>) ||
                  ornaments(<>) ||
                  annotation(<>) ]
Initial: normal
Applies to: all elements and text
Inherited: yes
Percentages: n/a
Computed value: as specified
Animation type: discrete

<feature-value-name> = <>

> with a custom <>, which is then used in this property to select specific alternates:

@font-feature-values Noble Script { @swash { swishy: 1; flowing: 2; } }

p {
  font-family: Noble Script;
  font-variant-alternates: swash(flowing); /* use swash alternate #2 */
}

When a particular <> has not been defined for a given family or for a particular feature type, the computed value must be the same as if it had been defined. However, property values that contain these undefined <> identifiers must be ignored when choosing glyphs.

/* these two style rules are effectively the same */

p { font-variant-alternates: swash(unknown-value); } /* not a defined value, ignored */
p { font-variant-alternates: normal; }

This allows values to be defined and used for a given set of font families but ignored if fallback occurs, since the font family name would be different. If a given value is outside the range supported by a given font, the value is ignored. These values never apply to generic font families. Individual values have the following meanings:

normal

None of the features listed below are enabled.

historical-forms

Enables display of historical forms (OpenType feature: hist).

stylistic(<>)

Enables display of stylistic alternates (font specific, OpenType feature: salt <>).

styleset(<>#)

Enables display with stylistic sets (font specific, OpenType feature: ss<> OpenType currently defines ss01 through ss20).

character-variant(<>#)

Enables display of specific character variants (font specific, OpenType feature: cv<> OpenType currently defines cv01 through cv99).

swash(<>)

Enables display of swash glyphs (font specific, OpenType feature: swsh <>, cswh <>).

ornaments(<>)

Enables replacement of default glyphs with ornaments, if provided in the font (font specific, OpenType feature: ornm <>). Some fonts may offer ornament glyphs as alternates for a wide collection of characters; however, displaying arbitrary characters (e.g., alphanumerics) as ornaments is poor practice as it distorts the semantics of the data. Font designers are encouraged to encode all ornaments (except those explicitly encoded in the Unicode Dingbats blocks, etc.) as alternates for the bullet character (U+2022) to allow authors to select the desired glyph using ''ornaments()''.

annotation(<>)

Enables display of alternate annotation forms (font specific, OpenType feature: nalt <>).

Defining font specific alternates: the @font-feature-values rule

Several of the possible values of 'font-variant-alternates' listed above are labeled as font specific; a font can define not just a single glyph for the feature, but multiple possible glyph variants, and associate each one with a numeric index to let you choose which to turn on. These numeric indexes are idiosyncratic to each face; a swsh 1 feature on one font face might turn on the swash version of capital Q, while on another font face it turns on the swash version of the &. Thus, specifying the index in 'font-feature-settings' requires that the author know exactly which font will be used on an element; if they get it wrong (due to font fallback selecting a different font) they might end up turning on an entirely different, and undesirable, feature to what they wanted! It also means that the author can't easily turn on similar features for elements with different fonts; they have to individually set different 'font-feature-settings' values for each that uses the correct numeric indexes for the desired features. To fix this issue, the ''@font-feature-values'' rule lets an author assign, for each font face, a human-friendly name to specific feature indexes. Using these friendly names, an author can easily turn on similar features regardless of the font in use (if they've defined that name for all the fonts), and be sure they're not accidentally turning on unrelated features (as fonts without those names defined for them simply won't do anything).

Using a commonly named value allows authors to use a single style rule to cover a set of fonts for which the underlying selector is different for each font. If either font in the example below is found, a circled number glyph will be used:

    @font-feature-values Otaru Kisa {
      @annotation { circled: 1; black-boxed: 3; }
    }
    @font-feature-values Taisho Gothic {
      @annotation { boxed: 1; circled: 4; }
    }

    h3.title {
      /* circled form defined for both fonts */
      font-family: Otaru Kisa, Taisho Gothic;
      font-variant: annotation(circled);
    }
    

Trying to turn on the "circled" forms for either font explicitly, using 'font-feature-values', would require the author know for certain which font will be used; if they expected "Otaru Kisa" and wrote ''font-feature-values: nalt 1;'', it would turn on "circled" characters in Otara Kisa, but would instead turn on boxed characters if the system fell back to Taisho Gothic, as that's what Taisho Gothic associates with nalt 1!

Basic syntax

An ''@font-feature-values'' rule's prelude contains a list of font family names, followed by a block containing multiple <>s, a special type of subsidiary at-rule. Each <> contains declarations mapping author-chosen human-friendly names (such as "flowing") to feature indexes for the associated feature.

@font-feature-values <># { <> }

<> = <> { <> }

<> = @stylistic | @historical-forms | @styleset | @character-variant
	| @swash | @ornaments | @annotation

alternates-order.html test_font_feature_values_parsing.html The ''@font-feature-values'' prelude is a comma-delimited list of font family names that match the definition of <> for the 'font-family!!property' property. This means that only named font families are allowed; rules that include generic or system fonts in the list of font families are syntax errors. However, if a user agent defines a generic font to be a specific named font (e.g. Helvetica), the settings associated with that family name will be used. If syntax errors occur within the <> list, the entire rule ''@font-feature-values'' rule is invalid and must be ignored. The ''@font-feature-values'' block accepts <> as its contents; these list items are either: [=at-rules=] named by one of the <> at-keyword tokens, or the '@font-feature-values/font-display' descriptor. Specifying the same <> more than once is valid; their contents are cascaded together. Each <> accepts a list of [=declarations=], the font feature value declarations, where the declaration's name can be any [=identifier=], and the value must be a list of one or more non-negative <>s. The <>s accept any declaration name; these names must be identifiers, per standard CSS syntax rules, and are [=case-sensitive=] (so ''foo: 1;'' and ''FOO: 2'' define two different features). Each declaration's value must match the grammar ''<>+'', or else the declaration is invalid and must be ignored. Note: Each feature name is unique only within a single <>. Between different <>s, or the same type of <>s in separate ''@font-feature-values'' rules, names can be reused without colliding. For each <> in the ''@font-feature-values'' prelude, each [=font feature value declaration=] defines a mapping between a (family name, feature block name, declaration name) [=tuple=] and the list of one or more integers from the declaration's value. If the same tuple appears more than once in a document (such as if a single block), the last-defined one is used.

For example, the following all define the exact same set of font feature values:

    /* Default */
    @font-feature-values foo {
        @swash { pretty: 1; cool: 2; }
    }

    /* Repeated declaration names */
    @font-feature-values foo {
        @swash { pretty: 0; pretty: 1; cool: 2; }
    }

    /* Multiple blocks of the same type */
    @font-feature-values foo {
        @swash { pretty: 1; }
        @swash { cool: 2; }
    }

    /* Multiple rules for the same family */
    @font-feature-values foo {
        @swash { pretty: 1; }
    }
    @font-feature-values foo {
        @swash { cool: 2; }
    }
    

A syntax error within a [=font feature value declaration=] makes the declaration invalid and ignored, but does not invalidate the [=font feature value block=] it occurs in. An unknown at-rule within a ''@font-feature-values'' block (not using one of the predefined list of allowed at-keywords) makes that at-rule invalid and ignored, but does not invalidate the ''@font-feature-values'' rule.

Rules that are equivalent given syntax error handling:

    @font-feature-values Bongo {
        @swash { ornate: 1; }
        annotation { boxed: 4; } /* should be @annotation! */
        @swash { double-loops: 1; flowing: -1; } /* negative value */
        @ornaments ; /* incomplete definition */
        @styleset { double-W: 14; sharp-terminals: 16 1 } /* missing ; */
        redrum  /* random editing mistake */
    }
    

The example above is equivalent to:

    @font-feature-values Bongo {
        @swash { ornate: 1; }
        @swash { double-loops: 1; }
        @styleset { double-W: 14; sharp-terminals: 16 1; }
    }
    

If multiple ''@font-feature-values'' rules are defined for a given family, the resulting values definitions are the union of the definitions contained within these rules. This allows a set of named values to be defined for a given font family globally for a site and specific additions made per-page.

Using both site-wide and per-page feature values: site.css:

    @font-feature-values Mercury Serif {
        @styleset {
            stacked-g: 3; /* "two-storey" versions of g, a */
            stacked-a: 4;
        }
    }
    

page.css:

    @font-feature-values Mercury Serif {
        @styleset {
           geometric-m: 7; /* alternate version of m */
        }
    }

    body {
        font-family: Mercury Serif, serif;

        /* enable both the use of stacked g and alternate m */
        font-variant-alternates: styleset(stacked-g, geometric-m);
    }
    

Multi-valued feature value definitions

Most font specific functional values of the 'font-variant-alternates' property take a single value (e.g. ''swash()''). The ''character-variant()'' property value allows two values and ''styleset()'' allows an unlimited number. For the styleset property value, multiple values indicate the style sets to be enabled. Values between 1 and 99 enable OpenType features ss01 through ss99. However, the OpenType standard only officially defines ss01 through ss20. For OpenType fonts, values greater than 99 or equal to 0 do not generate a syntax error when parsed but enable no OpenType features.

@font-feature-values Mars Serif {
	@styleset {
	alt-g: 1;        /* implies ss01 = 1 */
	curly-quotes: 3; /* implies ss03 = 1 */
	code: 4 5;       /* implies ss04 = 1, ss05 = 1 */
	}

	@styleset {
	dumb: 125;        /* >99, ignored */
	}

	@swash {
	swishy: 3 5;     /* more than 1 value for swash, syntax error */
	}
}

p.codeblock {
	/* implies ss03 = 1, ss04 = 1, ss05 = 1 */
	font-variant-alternates: styleset(curly-quotes, code);
}

For character-variant, a single value between 1 and 99 indicates the enabling of OpenType feature cv01 through cv99. For OpenType fonts, values greater than 99 or equal to 0 are ignored but do not generate a syntax error when parsed but enable no OpenType features. When two values are listed, the first value indicates the feature used and the second the value passed for that feature. If more than two values are assigned to a given name, a syntax error occurs and the entire feature value definition is ignored.

@font-feature-values MM Greek {
	@character-variant { alpha-2: 1 2; }   /* implies cv01 = 2 */
	@character-variant { beta-3: 2 3; }    /* implies cv02 = 3 */
	@character-variant { epsilon: 5 3 6; } /* more than 2 values, syntax error, definition ignored */
	@character-variant { gamma: 12; }      /* implies cv12 = 1 */
	@character-variant { zeta:   20 3; }   /* implies cv20 = 3 */
	@character-variant { zeta-2: 20 2; }   /* implies cv20 = 2 */
	@character-variant { silly: 105; }     /* >99, ignored */
	@character-variant { dumb: 323 3; }    /* >99, ignored */
}

#title {
	/* use the third alternate beta, first alternate gamma */
	font-variant-alternates: character-variant(beta-3, gamma);
}

p {
	/* zeta-2 follows zeta, implies cv20 = 2  */
	font-variant-alternates: character-variant(zeta, zeta-2);
}

.special {
	/* zeta follows zeta-2, implies cv20 = 3  */
	font-variant-alternates: character-variant(zeta-2, zeta);
}

Byzantine seal text displayed with character variants

In the figure above, the text in red is rendered using a font containing character variants that mimic the character forms found on a Byzantine seal from the 8th century A.D. Two lines below is the same text displayed in a font without variants. Note the two variants for U and N used on the seal.

@font-feature-values Athena Ruby {
	@character-variant {
	leo-B: 2 1;
	leo-M: 13 3;
	leo-alt-N: 14 1;
	leo-N: 14 2;
	leo-T: 20 1;
	leo-U: 21 2;
	leo-alt-U: 21 4;
	}
}

p {
	font-variant: discretionary-ligatures
				character-variant(leo-B, leo-M, leo-N, leo-T, leo-U);
}

span.alt-N {
	font-variant-alternates: character-variant(leo-alt-N);
}

span.alt-U {
	font-variant-alternates: character-variant(leo-alt-U);
}

<p>ENO....UP͞RSTU<span class="alt-U">U</span>͞<span class="alt-U">U</span>ΚΑΙTỤẠG̣IUPNS</p>

<p>LEON|ΚΑΙCONSTA|NTI<span class="alt-N">N</span>OS..|STOIBAṢ.|LIṢROM|AIO<span class="alt-N">N</span></p>

East Asian text rendering: the 'font-variant-east-asian' property

Name: font-variant-east-asian

Value: 	normal | [ <> || <> || ruby ]
Initial: normal
Applies to: all elements and text
Inherited: yes
Percentages: n/a
Computed value: as specified
Animation type: discrete

font-variant-east-asian-01.html font-variant-east-asian-02.html font-variant-east-asian-03.html font-variant-east-asian-04.html font-variant-east-asian-05.html font-variant-east-asian-06.html font-variant-east-asian-07.html font-variant-east-asian-08.html font-variant-east-asian-09.html font-variant-east-asian-10.html font-variant-east-asian.html parsing/font-variant-east-asian-computed.html parsing/font-variant-east-asian-invalid.html parsing/font-variant-east-asian-valid.html

Allows control of glyph substitution and sizing in East Asian text.

<east-asian-variant-values> = [ jis78 | jis83 | jis90 | jis04 | simplified | traditional ]

<east-asian-width-values>   = [ full-width | proportional-width ]

Individual values have the following meanings:

normal

None of the features listed below are enabled.

jis78

Enables rendering of JIS78 forms (OpenType feature: jp78).

jis83

Enables rendering of JIS83 forms (OpenType feature: jp83).

jis90

Enables rendering of JIS90 forms (OpenType feature: jp90).

jis04

Enables rendering of JIS2004 forms (OpenType feature: jp04).

The various JIS variants reflect the glyph forms defined in different Japanese national standards. Fonts generally include glyphs defined by the most recent national standard, but it's sometimes necessary to use older variants, to match signage for example.

simplified

Enables rendering of simplified forms (OpenType feature: smpl).

traditional

Enables rendering of traditional forms (OpenType feature: trad).

The 'simplified' and 'traditional' values allow control over the glyph forms for characters which have been simplified over time but for which the older, traditional form is still used in some contexts. The exact set of characters and glyph forms will vary to some degree by the context for which a given font was designed.

full-width

Enables rendering of full-width variants (OpenType feature: fwid).

proportional-width

Enables rendering of proportionally-spaced variants (OpenType feature: pwid).

ruby

Enables display of ruby variant glyphs (OpenType feature: ruby). Since ruby text is generally smaller than the associated body text, font designers can design special glyphs for use with ruby that are more readable than scaled down versions of the default glyphs. Only glyph selection is affected, there is no associated font scaling or other change that affects line layout. The red ruby text below is shown with default glyphs (top) and with ruby variant glyphs (bottom). Note the slight difference in stroke thickness.

Overall shorthand for font rendering: the 'font-variant!!property' property

Name: font-variant

Value: 	normal | none | [ [ <> || <> || <> || <> ] || [ small-caps | all-small-caps | petite-caps | all-petite-caps | unicase | titling-caps ] || [ stylistic(<>) || historical-forms || styleset(<>#) || character-variant(<>#) || swash(<>) || ornaments(<>) || annotation(<>) ] || [ <> || <> || <> || ordinal || slashed-zero ] || [ <> || <> || ruby ] || [ sub | super ] || [ text | emoji | unicode ] ]
Initial: normal
Applies to: all elements and text
Inherited: yes
Percentages: n/a
Computed value: as specified
Animation type: discrete

font-variant-01.html font-variant-02.html font-variant-03.html font-variant-04.html parsing/font-shorthand-variant.html parsing/font-variant-invalid.html parsing/font-variant-valid.html

The 'font-variant!!property' property is a shorthand for all font-variant subproperties: * 'font-variant-ligatures' * 'font-variant-position' * 'font-variant-caps' * 'font-variant-numeric' * 'font-variant-alternates' * 'font-variant-east-asian' * 'font-variant-emoji' The value 'normal' resets all subproperties of 'font-variant!!property' to their initial value. The 'none' value sets 'font-variant-ligatures' to 'none' and resets all other font feature properties to their initial value. Like other shorthands, using 'font-variant' resets unspecified 'font-variant' subproperties to their initial values.

It does not reset the values of 'font-language-override', 'font-feature-settings!!property' or 'font-variation-settings!!property'.

Low-level font feature settings control: the 'font-feature-settings!!property' property

Name: font-feature-settings

Value: 	normal | <>#
Initial: normal
Applies to: all elements and text
Inherited: yes
Percentages: n/a
Computed value: as specified
Animation type: discrete

font-features-across-space-1.html font-features-across-space-2.html font-features-across-space-3.html font-feature-settings-tibetan.html parsing/font-feature-settings-computed.html parsing/font-feature-settings-invalid.html parsing/font-feature-settings-valid.html

This property provides low-level control over OpenType font features. It is intended as a way of providing access to font features that are not widely used but are needed for a particular use case.

Authors should not use 'font-feature-settings!!property' to set any of the font features in the table below. Instead, please use the higher-level replacement properties, because:

1. The higher-level properties cascade individually. You can set one without setting the whole 'font-feature-settings!!property' list
2. Some higher-level properties can be synthesized for fonts that do not support the font feature.

If you want to set this font feature	then use this instead of 'font-feature-settings!!property'	Notes
Kerning (kern) or Vertical Kerning (vkrn)	'font-kerning!!property': ''font-kerning/normal''	The 'font-kerning!!property' property will set the kern or vkrn feature depending on the 'writing-mode'.
Standard Ligatures (liga) or Contextual Ligatures (clig)	'font-variant-ligatures!!property': ''font-variant-ligatures/common-ligatures''
Discretionary Ligatures (dlig)	'font-variant-ligatures!!property': ''font-variant-ligatures/discretionary-ligatures''
Historical Ligatures (hlig)	'font-variant-ligatures!!property': ''font-variant-ligatures/historical-ligatures''
Contextual Alternates (calt)	'font-variant-ligatures!!property': ''font-variant-ligatures/contextual''
Subscript (subs)	'font-variant-position!!property': ''font-variant-position/sub''
Superscript (sups)	'font-variant-position!!property': ''font-variant-position/super''
Small Capitals (smcp)	'font-variant-caps!!property': ''font-variant-caps/small-caps''
Small Capitals From Capitals (c2sc)	'font-variant-caps!!property': ''font-variant-caps/all-small-caps''
Petite Capitals (pcap)	'font-variant-caps!!property': ''font-variant-caps/petite-caps''
Petite Capitals From Capitals (c2pc)	'font-variant-caps!!property': ''font-variant-caps/all-petite-caps''
Unicase (unic)	'font-variant-caps!!property': ''font-variant-caps/unicase''
Titling (titl)	'font-variant-caps!!property': ''font-variant-caps/titling-caps''
Lining Figures (lnum)	'font-variant-numeric!!property': ''font-variant-numeric/lining-nums''
Oldstyle Figures (onum)	'font-variant-numeric!!property': ''font-variant-numeric/oldstyle-nums''
Proportional Figures (pnum)	'font-variant-numeric!!property': ''font-variant-numeric/proportional-nums''
Tabular Figures (tnum)	'font-variant-numeric!!property': ''font-variant-numeric/tabular-nums''
Fractions (frac)	'font-variant-numeric!!property': ''font-variant-numeric/diagonal-fractions''
Alternative Fractions (afrc)	'font-variant-numeric!!property': ''font-variant-numeric/stacked-fractions''
Ordinals (ordn)	'font-variant-numeric!!property': ''font-variant-numeric/ordinal''
Slashed Zero (zero)	'font-variant-numeric!!property': ''font-variant-numeric/slashed-zero''
Historical Forms (hist)	'font-variant-alternates!!property': ''font-variant-alternates/historical-forms''
Stylistic Alternates (salt)	'font-variant-alternates!!property': ''font-variant-alternates/stylistic()''	Define which alternate gets used by making an ''@font-feature-values'' rule
Character Variant 1 - Character Variant 99 (cv01 - cv99)	'font-variant-alternates!!property': ''font-variant-alternates/character-variant()''	Define which character variant gets used by making an ''@font-feature-values'' rule
Swash (swsh) or Contextual Swash (cswh)	'font-variant-alternates!!property': ''font-variant-alternates/swash()''	Define which swash gets used by making an ''@font-feature-values'' rule
Ornaments (ornm)	'font-variant-alternates!!property': ''font-variant-alternates/ornaments()''	Define which ornament gets used by making an ''@font-feature-values'' rule
Alternate Annotation Forms (nalt)	'font-variant-alternates!!property': ''font-variant-alternates/annotation()''	Define which annotation gets used by making an ''@font-feature-values'' rule
JIS78 Forms (jp78)	'font-variant-east-asian!!property': ''font-variant-east-asian/jis78''
JIS83 Forms (jp83)	'font-variant-east-asian!!property': ''font-variant-east-asian/jis83''
JIS90 Forms (jp90)	'font-variant-east-asian!!property': ''font-variant-east-asian/jis90''
JIS2004 Forms (jp04)	'font-variant-east-asian!!property': ''font-variant-east-asian/jis04''
Simplified Forms (smpl)	'font-variant-east-asian!!property': ''font-variant-east-asian/simplified''
Traditional Forms (trad)	'font-variant-east-asian!!property': ''font-variant-east-asian/traditional''
Full Widths (fwid)	'font-variant-east-asian!!property': ''font-variant-east-asian/full-width''
Proportional Widths (pwid)	'font-variant-east-asian!!property': ''font-variant-east-asian/proportional-width''
Ruby Notation Forms (ruby)	'font-variant-east-asian!!property': ''font-variant-east-asian/ruby''

For example, there is no font-variant value to control Scientific Inferiors (small numerals used in chemical formulae). Readability is enhanced by using them, so they must be enabled using font-feature-settings:

.chem {
	font-feature-settings: 'sinf'
}

The entire property value is set at once. Unlike the font-variant properties, there is no way to modify the inherited value by adding or removing individual features.

A value of 'normal' means that no change in glyph selection or positioning occurs due to this property.

Feature tag values have the following syntax:

<feature-tag-value> = <string> [ <integer> | on | off ]?

The <string> is a case-sensitive OpenType feature tag. As specified in the OpenType specification [[!OPENTYPE]], feature tags contain four ASCII characters. Tag strings longer or shorter than four characters, or containing characters outside the U+20–7E codepoint range are invalid. Feature tags need only match a feature tag defined in the font, so they are not limited to explicitly registered OpenType features. Fonts defining custom feature tags should follow the tag name rules defined in the OpenType specification [[!OPENTYPE-FEATURES]].

Feature tags not present in the font are ignored; a user agent must not attempt to synthesize fallback behavior based on these feature tags. The one exception is that user agents may synthetically support the kern feature with fonts that contain kerning data in the form of a 'kern' table but lack kern feature support in the 'GPOS' table.

In general, authors should use the 'font-kerning' property to explicitly enable or disable kerning since this property always affects fonts with either type of kerning data.

If present, a value indicates an index used for glyph selection. An <integer> value must be 0 or greater. A value of 0 indicates that the feature is disabled. For boolean features, a value of 1 enables the feature. For non-boolean features, a value of 1 or greater enables the feature and indicates the feature selection index. A value of 'on' is synonymous with 1 and 'off' is synonymous with 0. If the value is omitted, a value of 1 is assumed.

The computed value of font-feature-settings is a map, so any duplicates in the specified value must not be preserved. If the same feature tag appears more than once, the value associated with the last appearance supersedes any previous value for that axis.

The computed value contains the de-duplicated feature tags, sorted in ascending order by [=code unit=].

font-feature-settings: "sinf" 1;       /* sinf=1 enable Scientific Inferiors */
font-feature-settings: "sinf" on;      /* sinf=1 enable Scientific Inferiors */
font-feature-settings: 'sinf';         /* sinf=1 enable Scientific Inferiors */
font-feature-settings: "sinf" off;     /* sinf=0 disable Scientific Inferiors */
font-feature-settings: "sinf", 'twid'; /* sinf=1, twid=1 enable Scientific Inferiors and Third Widths */
font-feature-settings: "sinf" "twid";  /* invalid, need a comma-delimited list */
font-feature-settings: "silly" off;    /* invalid, tag too long */
font-feature-settings: "PKRN";         /* PKRN=1 enable custom feature */
font-feature-settings: sinf;           /* invalid, tag must be a string */

When values greater than the range supported by the font are specified, the behavior is explicitly undefined. For boolean features, in general these will enable the feature. For non-boolean features, out of range values will in general be equivalent to a 0 value. However, in both cases the exact behavior will depend upon the way the font is designed (specifically, which type of lookup is used to define the feature).

Implementations may choose to ignore turning off features which the OpenType specification says are always required, such as required ligatures "rlig".

font-variant-ligatures-11.optional.html

Although specifically defined for OpenType feature tags, feature tags for other modern font formats that support font features may be added in the future. Where possible, features defined for other font formats should attempt to follow the pattern of registered OpenType tags.

The Japanese text below will be rendered with half-width kana characters:

body { font-feature-settings: "hwid"; /* Half-width OpenType feature */ }

<p>毎日カレー食べてるのに、飽きない</p>

Font language override: the 'font-language-override' property

Name: font-language-override
Value: normal | <>
Initial: normal
Applies to: all elements and text
Inherited: yes
Percentages: N/A
Computed value: specified string or the keyword ''font-language-override/none''
Animation type: discrete

font-language-override-01.html font-language-override-02.html font-language-override-03.html parsing/font-language-override-computed.html parsing/font-language-override-invalid.html parsing/font-language-override-valid.html Normally, authors can control the use of language-specific glyph substitutions and positioning by setting the content language of an element, as described above:

<!-- Display text using S'gaw Karen specific features -->

	<p lang="ksw">...</p>

In some cases, authors may need to specify a language system that differs from the content language, for example due to the need to mimic another language's typographic traditions. The 'font-language-override!!property' property allows authors to explicitly specify the language system of the font, overriding the language system implied by the content language. Values have the following meanings:

normal

specifies that when rendering with OpenType fonts, the content language of the element is used to infer the OpenType language system

<>

single four-character case-sensitive OpenType language system tag, specifies the OpenType language system to be used instead of the language system implied by the language of the element. If the string is shorter than four characters, it is padded at the end with space (U+0020) characters such that the length is 4, before being matched.

Unknown OpenType language system tags are silently ignored, and do not affect glyph selection and placement.

The Universal Declaration of Human Rights has been translated into a wide variety of languages. In Turkish, Article 9 of this document might be marked up as below:

<body lang="tr">

<h4>Madde 9</h4>
<p>Hiç kimse keyfi olarak tutuklanamaz, alıkonulanamaz veya sürülemez.</p>

Here the user agent uses the value of the 'lang' attribute when rendering text and appropriately renders this text without 'fi' ligatures. There is no need to use the 'font-language-override!!property' property. However, a given font may lack support for a specific language. In this situation authors may need to use the typographic conventions of a related language that are supported by that font:

<body lang="mk">     <!-- Macedonian lang code -->

body { font-language-override: "SRB"; /* Serbian OpenType language tag */ }

<h4>Члeн 9</h4>
<p>Никoj чoвeк нeмa дa бидe пoдлoжeн нa прoизвoлнo aпсeњe, притвoр или прoгoнувaњe.</p>

As the content creator knows that font specified supports Serbian, the Macedonian text here will be rendered using Serbian typographic conventions.

Font Feature and Variation Resolution

As described in the previous section, font features and variations can be enabled in a variety of ways, either via the use of 'font-variant!!property', 'font-feature-settings!!property', 'font''font-variation-settings!!property' in a style rule or within an ''@font-face'' rule. The resolution order for the union of these settings is defined below. Features defined via CSS properties are applied on top of layout engine default features.

Default features

For OpenType fonts, user agents must enable the default features defined in the OpenType documentation for a given script and writing mode. Required ligatures, common ligatures and contextual forms must be enabled by default (OpenType features: rlig, liga, clig, calt), along with localized forms (OpenType feature: locl), and features required for proper display of composed characters and marks (OpenType features: ccmp, mark, mkmk). These features must always be enabled, even when the value of the 'font-variant!!property' and 'font-feature-settings!!property' properties is normal. Individual features are only disabled when explicitly overridden by the author, as when 'font-variant-ligatures!!property' is set to 'no-common-ligatures'. font-default-01.html font-default-02.html font-default-03.html font-default-04.html For handling complex scripts such as Arabic, Mongolian or Devanagari additional features are required. For upright text within vertical text runs, vertical alternates (OpenType feature: vert) must be enabled.

Feature and variation precedence

General and font specific font feature property settings are resolved in the order below, in ascending order of precedence. This ordering is used to construct a combined list of font features that affect a given text run. 1. Font features enabled by default are applied, including features required for a given script. See [[#default-features]] for a description of these. 2. Font variations as enabled by the 'font-weight!!property', 'font-stretch!!property', and 'font-style!!property' properties are applied. The application of the value enabled by 'font-style!!property' is affected by font selection, because this property might select an italic or an oblique font. The value applied is the closest matching value as determined by the font matching algorithm. User agents must apply at most one value due to the 'font-style!!property' property; both "ital" and "slnt" values must not be set together. If the selected font is defined in an ''@font-face'' rule, then the values applied at this step should be clamped to the value of the 'font-weight!!descriptor', 'font-stretch!!descriptor', and 'font-style!!descriptor' descriptors in that ''@font-face'' rule. Then, the values applied in this step should be clamped (possibly again) to the values that are supported by the font. 3. The language specified by the inherited value of lang/xml:lang is applied. 4. If the font is defined via an ''@font-face'' rule, the font language override implied by the 'font-language-override!!descriptor' descriptor in the ''@font-face'' rule is applied. 5. If the font is defined via an ''@font-face'' rule, that ''@font-face'' rule includes at least one valid 'font-named-instance' descriptor with a value other than 'font-named-instance/none', and the loaded font resource includes a named instance with that name according to the [[#localized-name-matching]] rules, then all the variation values represented by that named instance are applied. These values are clamped to the values that are supported by the font. 6. If the font is defined via an ''@font-face'' rule, the font variations implied by the 'font-variation-settings!!descriptor' descriptor in the ''@font-face'' rule are applied. 7. If the font is defined via an ''@font-face'' rule, the font features implied by the 'font-feature-settings!!descriptor' descriptor in the ''@font-face'' rule are applied. 8. The font language override implied by the value of the 'font-language-override!!property' property is applied. 9. Font variations implied by the value of the 'font-optical-sizing!!property' property are applied. 10. Font features implied by the value of the 'font-variant!!property' property, the related 'font-variant!!property' subproperties and any other CSS property that uses OpenType features (e.g. the 'font-kerning!!property' property) are applied. 11. Feature settings determined by properties other than 'font-variant!!property' or 'font-feature-settings!!property' are applied. For example, setting a non-default value for the 'letter-spacing' property disables optional ligatures. 12. Font variations implied by the value of the 'font-variation-settings!!property' property are applied. These values should be clamped to the values that are supported by the font. 13. Font features implied by the value of 'font-feature-settings!!property' property are applied. font-feature-resolution-001.html font-feature-resolution-002.html This ordering allows authors to set up a general set of defaults for fonts within their ''@font-face'' rules, then override them with property settings for specific elements. General property settings override the settings in ''@font-face'' rules and low-level font feature settings override 'font-variant!!property' property settings. For situations where the combined list of font feature settings contains more than one value for the same feature, the last value is used. When a font lacks support for a given underlying font feature, text is simply rendered as if that font feature was not enabled; font fallback does not occur and no attempt is made to synthesize the feature except where explicitly defined for specific properties.

Feature precedence examples

With the styles below, numbers are rendered proportionally when used within a paragraph but are shown in tabular form within tables of prices:

	body {
	  font-variant-numeric: proportional-nums;
	}

	table.prices td {
	  font-variant-numeric: tabular-nums;
	}
	

The ''@font-face'' rule can also be used to access font features in locally available fonts via the use of local() in the 'src!!descriptor' descriptor of the ''@font-face'' definition:

	@font-face {
	  font-family: BodyText;
	  src: local("HiraMaruPro-W4");
	  font-variant: proportional-width;
	  font-feature-settings: "ital"; /* Latin italics within CJK text feature */
	}

	body { font-family: BodyText, serif; }
	

If available, a Japanese font "Hiragino Maru Gothic" will be used. When text rendering occurs, Japanese kana will be proportionally spaced and Latin text will be italicized. Text rendered with the fallback serif font will use default rendering properties.

In the example below, discretionary ligatures are enabled only for a downloadable font but are disabled within spans of class "special":

	@font-face {
	  font-family: main;
	  src: url(fonts/ffmeta.woff) format("woff");
	  font-variant: discretionary-ligatures;
	}

	body         { font-family: main, Helvetica; }
	span.special { font-variant-ligatures: no-discretionary-ligatures; }
	

Suppose one adds a rule using 'font-feature-settings' to enable discretionary ligatures:

	body         { font-family: main, Helvetica; }
	span         { font-feature-settings: "dlig"; }
	span.special { font-variant-ligatures: no-discretionary-ligatures; }
	

In this case, discretionary ligatures will be rendered within spans of class "special". This is because both the 'font-feature-settings' and 'font-variant-ligatures' properties apply to these spans. Although the ''no-discretionary-ligatures'' setting of 'font-variant-ligatures' effectively disables the OpenType "dlig" feature, because the 'font-feature-settings' is resolved after that, the "dlig" value reenables discretionary ligatures.

Font Variation Properties

Note: The technology in use in this section is named "font variations." An instance of one such font as a "variable font."

Optical sizing control: the 'font-optical-sizing' property

Name: font-optical-sizing
Value: auto | none
Initial: auto
Applies to: all elements and text
Inherited: yes
Percentages: n/a
Computed value: specified keyword
Animation type: discrete

parsing/font-optical-sizing-computed.html parsing/font-optical-sizing-invalid.html parsing/font-optical-sizing-valid.html Typographically, text rendered at different sizes often benefits from slightly different visual representations. For example, to aid reading at small text sizes, strokes are often thicker with larger serifs. Larger text often has a more delicate figure with more contrast between thicker and thinner strokes.

auto

The user agent may modify the shape of glyphs based on the font-size and the pixel density of the screen. For OpenType and TrueType fonts using font variations, this is often done by using the "opsz" font variation.

none

The user agent must not modify the shape of glyphs for optical size.

'font-size' must be considered when selecting a variation value for the "opsz" axis, but other signals may also be considered. Note: User agents are expected to supply a value for the "opsz" axis which is close to the used value for 'font-size'. However, user agents might wish to consider other factors such as pixel density of the screen, or the solid angle the text subtends in the viewer's retina. Experiments have shown, however, that disregarding these other ancillary factors and using only 'font-size' might be the best way for a user agent to select this value. Pixel density as well as visual size of the text may influence the variation value chosen for 'font-optical-sizing'. When either pixel density or visual size of the text changes in response to a user operation or style change, user agents must not choose a new value for this variation value unless the change is layout-causing. User agents are free to determine which changes are layout-causing. Note: Some user operations, such as pinch-zoom, can be considered not-layout-causing if they do not cause text to reflow. However, other user operations, such as increasing text size for accessibility purposes, can be considered layout-causing because they cause text to reflow. Similarly, the 'transform' property can be considered not-layout-causing because transforms generally do not cause text to reflow. Each user-agent is free to decide whether or not each operation is layout-changing or not. User agents must not synthesize optical sizing when it is not performed by the font directly. User agents must not select a value for the "opsz" axis which is not supported by the font used for rendering the text. This can be accomplished by clamping a chosen value to the range supported by the font. 'font-optical-sizing' interacts with 'font-size-adjust'. When applying optical sizing, User agents must apply an optical sizing value appropriate for the adjusted font size, subject to the above restrictions.

Low-level font variation settings control: the 'font-variation-settings' property

Name: font-variation-settings
Value: normal | [ <> <>]#
Initial: normal
Applies to: all elements and text
Inherited: yes
Percentages: n/a
Computed value: the keyword ''font-variation-settings/normal'' or a list, each item a string paired with a number
Animation type: (see prose)

variations/variable-box-font.html variations/variable-gpos-m2b.html variations/variable-gsub.html variations/variable-opsz-size-adjust.html variations/variable-opsz.html This property provides low-level control over OpenType or TrueType font variations. It is intended as a way of providing access to font variations that are not widely used but are needed for a particular use case.

Authors should not use 'font-variation-settings!!property' to set any of the variation axes in the table below. Instead, please use the higher-level replacement properties, because:

1. The higher-level properties cascade individually. You can set one without setting the whole 'font-variation-settings!!property' list
2. Some higher-level properties can be synthesized for fonts that do not support the font variation.

If you want to set this variation axis	then use this instead of 'font-variation-settings!!property'	Notes
Weight (wght)	'font-weight!!property'	The 'font-weight!!property' property will set the wght axis if one is present.
Width (wdth)	'font-stretch!!property'	The 'font-stretch!!property' property will set the wdth axis if one is present.
Slant (slnt) or Italic (ital)	'font-style!!property'	The 'font-style!!property' property will set the slnt or ital axis, depending on its value.
Optical size (opsz)	'font-optical-sizing!!property'	The 'font-optical-sizing!!property' property will set the opsz axis if one is present.

The use of font variation settings does not affect font selection where a fallback font is to be used, where using font properties for the same axis would have an effect on font selection. When possible, authors should generally use the other properties related to font variations (such as 'font-optical-sizing'), and only use this property for special cases where its use is the only way of accessing a particular infrequently used font variation. For example, it is preferable to use 'font-weight!!property': 700 rather than 'font-variation-settings': "wght" 700. A value of ''font-variation-settings/normal'' means that no change in glyph shape, matching, or positioning occurs due to this property. The <> is a case-sensitive OpenType or TrueType variation axis name. As specified in the OpenType / TrueType specifications, axis names contain four ASCII characters. Axis name strings longer or shorter than four characters, or containing characters outside the U+20–7E codepoint range are invalid. Axis names need only match an axis tag defined in the font, so they are not limited to explicitly registered OpenType / TrueType variation axes. Fonts defining custom axis names should follow the name rules defined in the OpenType specification. If a given axis is not supported by a font, its value setting is ignored and therefore has no effect; a user agent must not attempt to synthesize fallback behavior based on these axis tags. Other axis values within the same CSS 'font-variation-settings' statement are not ignored. If a variation axis is supported by a font but its set value is greater or less than the predefined font range, it will be clamped to the closest value supported by the font. Values are allowed to be fractional or negative. Note: it is preferable to obtain slanted faces by using the 'font-style!!property' property. However, if using the slnt axis directly, via 'font-variation-settings', remember that it is defined with a positive angle meaning a counter-clockwise slant, the opposite direction to CSS. If the same axis name appears more than once, the value associated with the last appearance supersedes any previous value for that axis. This deduplication is observable by accessing the computed value of this property.

The computed value contains the de-duplicated axis names, sorted in ascending order by [=code unit=].

Although specifically defined for OpenType / TrueType variations, variation axes for other modern font formats that support font variations might be added in the future. Where possible, variations defined for other font formats should attempt to follow the pattern of registered variation axes. Animating font-variation-settings is possible using the following mechanism. Two declarations of font-feature-settings can be animated between if they are "like". "Like" declarations are ones where the same set of properties appear (in any order). Because successive duplicate properties are applied instead of prior duplicate properties, two declarations can be "like" even if they have differing number of properties. If two declarations are "like" then animation occurs pairwise between corresponding values in the declarations. Otherwise, animation is not possible. In this situation, the "from" values of the animation are swapped to the "to" values at an unspecified time during the animation.

Color Font Support

Color fonts allow for font files to describe, not just the contours describing the edges of glyphs, but also the colors present inside the glyphs.

For some uses, such as emoji, having the colors fixed in the font is appropriate. For others, there is a need to control the colors used from a stylesheet. font-colorization.html CSS provides two ways to do this. The 'font-palette' property allows selecting one of several different palettes contained in the font, or alternatively, forcing colored glyphs not to be used. The ''@font-palette-values'' rule allows overriding one or more colors from within a palette or even the creation of an entirely different palette.

Controlling Color Font Palettes: The 'font-palette' property

Many color font file formats allow colors within glyphs to be parameterized. In these fonts, colors are referenced by index when describing the geometry of each glyph. These indices are resolved within a current active palette using a lookup table present inside the font. However, many fonts contain multiple palettes, each containing a set of complementary colors chosen by the font designer to provide pleasing visual results. In addition, some color font file formats provide a regular, uncolored glyph outline as well as the colored versions.

Name: font-palette
Value: normal | light | dark | <>
Initial: normal
Applies to: all elements and text
Inherited: yes
Percentages: N/a
Computed value: specified keyword or identifier
Animation type: discrete

font-palette-10.html font-palette-11.html font-palette-12.html font-palette-13.html font-palette-14.html font-palette-15.html font-palette-16.html font-palette-17.html font-palette-18.html font-palette-19.html font-palette-2.html font-palette-20.html font-palette-21.html font-palette-22.html font-palette-23.html font-palette-24.html font-palette-25.html font-palette-26.html font-palette-27.html font-palette-28.html font-palette-29.html font-palette-3.html font-palette-30.html font-palette-31.html font-palette-32.html font-palette-33.html font-palette-34.html font-palette-35.html font-palette-4.html font-palette-5.html font-palette-6.html font-palette-7.html font-palette-8.html font-palette-9.html font-palette-add-2.html font-palette-add.html font-palette-empty-font-family.html font-palette-modify-2.html font-palette-modify.html font-palette-remove-2.html font-palette-remove.html font-palette.html font-palette-vs-shorthand.html parsing/font-palette-computed.html parsing/font-palette-invalid.html parsing/font-palette-valid.html

normal

User-Agents display the color font with the default palette or default glyph colorisation. User-agents should take the computed value of the color property into consideration when a color font format requires use of the foreground color

In the COLR [[!OPENTYPE]] table, color index 0xFFFF should be rendered according the 'color' property.

For COLR/CPAL [[!OPENTYPE]] fonts, 'font-palette': ''font-palette/normal'' usually means rendering the font with the palette in the font at index 0.

light

Some color font formats include metadata marking certain palettes as applicable on a light (close to white) background. This keyword causes the user-agent to use the first available palette in the font file marked this way. If the font file format does not account for this metadata, or no palette in the font is marked this way, this value behaves as ''font-palette/normal''.

dark

Some color font formats include metadata marking certain palettes as applicable on a dark (close to black) background. This keyword causes the user-agent to use the first available palette in the font file marked this way. If the font file format does not account for this metadata, or no palette in the font is marked this way, this value behaves as ''font-palette/normal''.

<>

This value identifies an CSS-defined palette to use. Users can define a palette by using the ''@font-palette-values'' rule. If no applicable ''@font-palette-values'' rule is present, this value behaves as ''font-palette/normal''. <> is parsed as a <>. Note: Such a CSS-defined palette may be a reference to an existing palette already present in the font, be a modification of an existing palette already present in the font, or be an entirely new palette.

Note: The names 'light' and 'dark' describe the background the color palette is usable on, not the colors in the color palette themselves.

When dark mode is in effect, use a dark mode palette

@media (prefers-color-scheme: dark) {
		.banner {font-palette: dark;
		}
	}
	

Issue: Add more examples and pictures.

User-defined font color palettes: The ''@font-palette-values'' rule

The @font-palette-values rule defines a color palette and associates that color palette with a specific font. This allows a web author to select arbitrary colors to use inside a color font rather than being limited to the preexisting palettes inside font files. In addition, this rule's association with a specific font allows a name of a palette to apply differently to different fonts, which allows similar colors to be used across multiple fonts when multiple fonts are used in an element (i.e. for font fallback). Note: A web author might wish to create multiple palettes for a single font in order to create multiple themes for their web content. A web author might also wish to create matching palettes for multiple fonts to achieve a consistent design across a collection of different fonts. A ''@font-palette-values'' rule represents a palette of colors used in a font. A palette consists of an ordered collection of colors. Using the ''@font-palette-values'' allows a web author to reference a palette existing within a font as well as creating a palette populated with author-defined colors. In addition, it allows overriding a set of colors from a palette in the font with colors described by the web author. A palette is always complete, meaning that it is impossible to describe a palette which has missing colors. If colors would be missing, they are taken from the palette within the font identified by the 'base-palette' descriptor. Functions such as ''calc()'', ''var()'', and ''env()'' are valid within the braces of a ''@font-palette-values'' rule. They are evaluated within the context of the root element. Relative units are also evaluated within the context of the root element. The ''@font-palette-values'' rule consists of the ''@font-palette-values'' at-keyword followed by a block of descriptor declarations. It has the following syntax:

        @font-palette-values <> {
            <>
        }
    

palette-values-rule-add-2.html palette-values-rule-add.html palette-values-rule-delete-2.html palette-values-rule-delete.html parsing/font-palette-values-invalid.html parsing/font-palette-values-valid.html The ''@font-palette-values'' rule accepts the descriptors defined in this specification.

Modify Bixa Color's color palette.

        @font-palette-values --Cooler {
            font-family: Bixa;
            base-palette: 1;
            override-colors:
                1 #7EB7E4;
        }
		

Modify Handover Sans's color palette

        @font-palette-values --Augusta {
            font-family: Handover Sans;
            base-palette: 3;
            override-colors:
                1 rgb(43, 12, 9),
                3 var(--highlight);
        }
        

These descriptors apply solely within the context of the ''@font-palette-values'' rule in which they are defined, and do not apply to document language elements. When a given descriptor occurs multiple times in a given ''@font-palette-values'' rule, only the last descriptor declaration is used and all prior declarations for that descriptor are ignored. Each of these palettes are applied to each @font-face that share a family name.

I want to use two color fonts in a greenish palette. The first font, Bixxxa, already has palette that I can use, but for Bungeehee I need to overwrite one color to get my green palette.

			@font-face {
				font-family: Bixxxa;
				src: url('./bixxxa.woff') format('woff');
			}

			@font-face {
				font-family: Bungeehee;
				src: url('./bungeehee.woff') format('woff');
			}

			@font-palette-values --ToxicGreen {
			  font-family: Bixxxa;
			  base-palette: 3; /* This is Bixxxa's green palette */
			}


			@font-palette-values --ToxicGreen {
			  font-family: Bungeehee;
			  base-palette: 7; /* This is Bungeehee's green palette... */
			  override-colors: 2 lime; /* ...except this is pink, which I overwrite to lime */
			}

			h1 {
				font-family: Bixxxa;
				font-palette: --ToxicGreen;
			}

			h2 {
				font-family: Bungeehee;
				font-palette: --ToxicGreen;
			}
		

Example by Roel Nieskens

Note: In the case where a family name is shared between multiple physical fonts, (such as when a compound font is created, using 'unicode-range!!descriptor'), and if those fonts have different palettes, the result of specifying a partial palette using ''@font-palette-values'' is unlikely to be what the author intended. In this case, it is better to supply a complete palette definition.

In the above example, since two different font families have been set up to have compatible named palettes, one could go on to write

			h3 {
				font-family: Bixxxa, Bungeehee;
				font-palette: --ToxicGreen;
			}
		

Which would correctly apply the desired palette in each font even though they have different palette numbers.

A given set of ''@font-palette-values'' rules define which author-defined palettes are available for use within the documents that contain these rules. An author-defined font color palette must only be available to the documents that reference it. Using an author-defined color palette outside of the documents that reference it would constitute a security leak since the contents of one page would be able to affect other pages, something an attacker could use as an attack vector. This at-rule follows the forward-compatible parsing rules of CSS. Like properties in a declaration block, declarations of any descriptors that are not supported by the user agent must be ignored. ''@font-palette-values'' rules require a '@font-palette-values/font-family' descriptor; if it is missing, the ''@font-palette-values'' rule is invalid and must be ignored entirely. In cases where user agents have limited platform resources, do not implement support for color fonts, or implement the ability to disable color fonts, ''@font-palette-values'' rules must simply be ignored; the behavior of individual descriptors as defined in this specification should not be altered.

Font family: the 'font-family!!descriptor' descriptor

    Name: font-family
	Value: <>#
    For: @font-palette-values
    Initial: N/A
    

This descriptor defines the font families that this palette applies to, using the same list of font families as [[#font-matching-algorithm]]. This palette will only ever be applied to the fonts with these family names. The value of this descriptor means that only named font families are allowed and rules that include generic fonts in the list of font families are syntax errors. If syntax errors occur within the font family list, the descriptor must be ignored (will still be in the CSS OM, but will not match any font families).

Specifying the base palette: the 'base-palette' descriptor

    Name: base-palette
    Value: light | dark | <>
    For: @font-palette-values
    Initial: N/A
    

light

Some color font formats include metadata marking certain palettes as applicable on a light (close to white) background. This keyword identifies the first available palette in the font file marked this way. If the font file format does not account for this metadata, or no palette in the font is marked this way, this value behaves as 0.

dark

Some color font formats include metadata marking certain palettes as applicable on a dark (close to black) background. This keyword identifies the first available palette in the font file marked this way. If the font file format does not account for this metadata, or no palette in the font is marked this way, this value behaves as 0.

<>

Identifies a (zero-based) numerical palette index within the font.

Modify Banner Flag's color palette

            @font-palette-values --Festival {
                font-family: Banner Flag;
                base-palette: 1;
                override-colors:
                    0 rgb(123, 64, 27),
                    1 darkblue,
                    2 var(--highlight);
            }
            

This descriptor specifies a palette in the font which the containing ''@font-palette-values'' rule uses as an initial value. If no <> key is present in the ''@font-palette-values'' rule, then the ''@font-palette-values'' rule represents the palette in the font with the same index as the value of this descriptor. If a <> key is present in the ''@font-palette-values'' rule, each item in the value of that descriptor overrides a single color in the color palette represented by this ''@font-palette-values'' block.

Rename Handover Sans's 3rd color palette

        @font-palette-values --Augusta {
            font-family: Handover Sans;
            base-palette: 3;
        }
        

If this descriptor is not present in the ''@font-palette-values'', or if the font does not contain a palette at the index of the value of 'base-palette', it behaves as if ''0'' were specified. If a font does not contain any color palettes, no colors are included in the initial color palette represented by this ''@font-palette-values'' rule. Colors in the palette can be overridden by using the 'override-color!!descriptor' descriptor in the ''@font-palette-values'' rule.

Overriding a colors from a palette: The 'override-colors!!descriptor' descriptor

    Name: override-colors
    Value: [ <> <> ]#
    For: @font-palette-values
    Initial: N/A
    

This descriptor overrides colors to the initial color palette represented by this ''@font-palette-values'' rule. The '@font-palette-values/override-colors' descriptor takes a comma-separated list of palette index entries and colors. Each item in the comma-separated list represents a tuple of an entry into the palette and a color to replace it with. For each key/value pair in the value of this descriptor, the color with that key in the initial palette (i.e. by using the 'base-palette' descriptor) is overwritten by the color specified in this descriptor's value. A key that is outside the range of indices of the initial palette is ignored. Palette index entries in the ''@font-palette-values/override-colors'' descriptor are a (zero-based) palette index entry. Integer values are zero-indexed. If the keys of multiple distinct key/value pairs identify the same color index (either by name or by integer), the last key is used for the purposes of rendering. However, for serialization purposes, both key/value pairs are present. Note: This means that using 'font-palette' with the same value on two different elements might result in different used palettes because the value of variables inside the ''@font-palette-values'' rule might apply differently in the context of those two elements. Colors provided from CSS (as overrides, or as new entries) may use any supported colorspace. Note: The colors specified in versions 0 and 1 of the CPAL table are in sRGB.

Selecting the text presentation style: The 'font-variant-emoji' property

Name: font-variant-emoji
Value: normal | text | emoji | unicode
Initial: normal
Applies to: all elements and text
Inherited: yes
Percentages: N/a
Computed value: specified keyword
Animation type: discrete

font-variant-emoji-1.html font-variant-emoji-2.html parsing/font-variant-emoji-computed.html parsing/font-variant-emoji-invalid.html parsing/font-variant-emoji-valid.html This property allows web authors to select whether emoji presentation or text presentation is used for certain emoji code points. Traditionally, these presentation styles were selected by appending Variation Selector 15 (U+FE0E) or Variation Selector 16 (U+FE0F) to certain code points. However, 'font-variant-emoji' allows web authors to set a default presentation style which can replace the variation selectors. Only the code points listed by Unicode as contributing to a Unicode emoji presentation sequence are affected by this property. Within this CSS specification, these characters are referred to as Emoji Presentation Participating Code Points. This property has no effect on any other characters. This property is expected to affect font fallback; however, the exact nature of the interaction of font fallback with 'font-variant-emoji' is explicitly unspecified. However, a variation selector must be included in a previous cluster as defined by the cluster matching section above. Therefore, the presence of a variation selector is treated as ancillary data to inform the font fallback routine. A natural result of this behavior is that a variation selector must not be rendered in a different font than the previous character. Even when 'font-variant-emoji' is used, the presence of Variation Selector 15 (U+FE0E) or Variation Selector 16 (U+FE0F) in the contents of an element override the rendering specified in 'font-variant-emoji'. Therefore, 'font-variant-emoji' sets a default presentation which the text being rendered can opt out of. Note: Different platforms have different conventions about how to handle emoji presentation sequences. A cross-platform UA might wish to follow the conventions of each individual platform, or it might wish to use the same approach on all platforms. When tasked with a request for an emoji style rendering, a UA might wish to disregard fonts which do not include color tables. A different UA might wish instead to use the same mechanical cluster fallback algorithm that it would use for any arbitrary cluster. Variation selectors other than FE0E VARIATION SELECTOR-15 and U+FE0F VARIATION SELECTOR-16 must not have any effect on font selection. If one of these variation selectors is present, but unsupported by the font previously selected, the variation selector is ignored. BCP47's -u- extension to the language tag accepted by lang or xml:lang should not be considered when the user-agent decides whether to use emoji presentation or text presentation for a particular character.

normal

User agents can choose to draw a Presentation Participating Code Point in either emoji style or text style. User agents typically follow platform conventions when performing this decision.

text

Code points are rendered as if U+FE0E VARIATION SELECTOR-15 was appended to every Presentation Participating Code Point.

emoji

Code points are rendered as if U+FE0F VARIATION SELECTOR-16 was appended to every Presentation Participating Code Point.

unicode

Code points are rendered in accordance with [[!UTS51]] as either emoji-default, text-default, or text-only, depending on the values of the Emoji and Emoji_Presentation properties for each Presentation Participating Code Point. If present, FE0E VARIATION SELECTOR-15 and U+FE0F VARIATION SELECTOR-16 will override the default presentation of individual Presentation Participating Code Points.

To show the emoji form of U+1F6CB COUCH AND LAMP, let CustomEmoji.ttf obey the user agent's notion of supporting the emoji form of this character, and use the following:

	@font-face {
		font-family: "Custom Emoji";
		src: url("CustomEmoji.ttf") format("truetype");
	}
	...
	<div style="font-family: 'Custom Emoji'; font-variant-emoji: emoji;">&#x1F6CB;</div>
	

Font Taxonomy

A given font may belong in one or more of the following categories:

Installed Fonts

A font may be installed globally on a device. Such fonts are generally accessible in any application, even applications which have no concept of CSS. The file or files backing the font object exist on the user's device, not as a remote resource. The set of installed fonts available in the Font Matching Algorithm is explicitly undefined. Installed Fonts must not be Web Fonts, and Web Fonts must not be Installed Fonts.

Web Fonts

A font may be backed by a remote resource, which must be requested using the user agent's resource fetching infrastructure. Web Fonts are represented by one of two mechanisms: - ''@font-face'' rules - A ''FontFace'' member of the Document's ''FontFaceSet'' A Web Font must not be accessible in any other Document from the one which either is associated with the ''@font-face'' rule or owns the ''FontFaceSet''. Other applications on the device must not be able to access Web Fonts. Installed Fonts must not be Web Fonts, and Web Fonts must not be Installed Fonts. Web Fonts shadow Installed Fonts, so if an Installed Font has the same family name as a Web Font, the Installed Font is not accessible.

Preinstalled Fonts and User-Installed Fonts

Users can choose to install fonts on their devices. User-Installed Fonts are installed by an explicit action by the user, such as clicking an "Install" button or copying a file into a particular directory on their device. Such fonts are User-Installed Fonts and also are Installed Fonts. Web content authors should not count on the presence of user-installed fonts, because there is no guarantee any user will have performed the action to install a specific font. User agents may choose to ignore User-Installed Fonts for the purpose of the Font Matching Algorithm. Any Installed Font which is not a User-Installed font is a Preinstalled Font. It is likely that all users of a particular version of a particular Operating System will have the same set of Preinstalled Fonts installed. As such, Web content authors targeting these Operating Systems may wish to use these fonts' family names inside 'font-family!!property' properties.

System Font

The System Font is the font which is used by the ''system-ui'' generic font family name. It is an example of a Preinstalled Font. system-ui-ar.html system-ui-ja-vs-zh.html system-ui-ja.html system-ui-mixed.html system-ui-ur-vs-ar.html system-ui-ur.html system-ui-zh.html system-ui.html

Font Technologies and Formats

Font tech

The 'features-opentype', 'features-aat' and 'features-graphite' techs refer to support for font features, commonly implemented in [[!OPENTYPE]] with the GSUB and the GPOS tables, as well as in [[!AAT-FEATURES]] using the morx and kerx tables and [[!GRAPHITE]] with the Silf, Glat , Gloc , Feat and Sill tables as documented in the Graphite Table Format. The section on [[#font-rend-props]] describes properties that interact with these facilities. The 'variations' tech refers to the support of font variations, commonly implemented in [[!OPENTYPE]] with the avar, cvar, fvar, gvar, HVAR, MVAR, STAT, and VVAR tables, as well as in [[!AAT-FEATURES]] using the avar, cvar, fvar, gvar tables. The section on [[#basic-font-props]] as well as the section on [[#font-variation-props]] describe properties that interact with these facilities. The 'color-colrv0', 'color-colrv1', 'color-svg', 'color-sbix' and 'color-cbdt' technologies refers to various types of color font file technologies. Each one represents a table (COLR, SVG, sbix or CBDT) inside [[!OPENTYPE]] or [[!AAT-FEATURES]] fonts which must be supported to satisfy this requirement. The 'palettes' tech refers to support for font palettes, commonly implemented in the [[!OPENTYPE]] and [[!AAT-FEATURES]] with the CPAL table. The section on [[#color-font-support]] describes properties that interact with these facilities. The 'incremental-patch', 'incremental-range' and 'incremental-auto' techs refer to client support for incremental font transfer [[IFT]], using the patch-subset, range-request, or automatic negotiation between these two methods.

For background on these, see [[PFE-report]].

Web authors can specify the 'tech' function inside an ''@font-face'' 'src!!descriptor' descriptor to indicate that support is required for correct rendering of a font. This mechanism can be used for gracefully falling back to an ancillary font when requested support is not present.

This ''@font-face'' block shows how to use a color font if support is present on the user agent, and falls back to a non-color-font if support is not present.

    @font-face {
        font-family: "Trickster";
        src: url("trickster-COLRv1.otf") format(opentype) tech(color-COLRv1),
		url("trickster-outline.otf") format(opentype);
    }
    

Font formats

Format strings defined by this specification are as follows. The <> values are synonyms for the formats below.

String	Font Format	Common extensions
"collection"	OpenType Collection	.otc,.ttc
"embedded-opentype"	Embedded OpenType	.eot
"opentype"	OpenType	.ttf, .otf
"svg"	SVG Font (deprecated)	.svg, .svgz
"truetype"	TrueType	.ttf
"woff"	WOFF 1.0 (Web Open Font Format)	.woff
"woff2"	WOFF 2.0 (Web Open Font Format)	.woff2

Given the overlap in common usage between TrueType and OpenType, the format hints "truetype" and "opentype" must be considered as synonymous; a format hint of "opentype" does not imply that the font contains Postscript CFF style glyph data or that it contains OpenType layout information (see Appendix A for more background on this).

Object Model

The contents of ''@font-face'' and ''@font-feature-values'' rules can be accessed via the following extensions to the CSS Object Model. idlharness.html

The CSSFontFaceRule interface

The CSSFontFaceRule interface represents a <<@font-face>> rule.

[Exposed=Window]
interface CSSFontFaceRule : CSSRule {
    readonly attribute CSSStyleDeclaration style;
};

The CSSFontFeatureValuesRule interface

The CSSRule interface is extended as follows:

partial interface CSSRule {
  const unsigned short FONT_FEATURE_VALUES_RULE = 14;
};

The CSSFontFeatureValuesRule interface represents a @font-feature-values rule.

[Exposed=Window]
interface CSSFontFeatureValuesRule : CSSRule {
  attribute CSSOMString fontFamily;
  readonly attribute CSSFontFeatureValuesMap annotation;
  readonly attribute CSSFontFeatureValuesMap ornaments;
  readonly attribute CSSFontFeatureValuesMap stylistic;
  readonly attribute CSSFontFeatureValuesMap swash;
  readonly attribute CSSFontFeatureValuesMap characterVariant;
  readonly attribute CSSFontFeatureValuesMap styleset;
};

[Exposed=Window]
interface CSSFontFeatureValuesMap {
  maplike<CSSOMString, sequence<unsigned long>>;
  undefined set(CSSOMString featureValueName,
           (unsigned long or sequence<unsigned long>) values);
};

fontFamily of type CSSOMString

The list of one or more font families for which a given set of feature values is defined.

value maps of type CSSFontFeatureValuesMap, readonly

Maps of feature values associated with feature value names for a given 'font-variant-alternates' value type

Each value map attribute of CSSFontFeatureValuesRule reflects the values defined via a corresponding feature value block. Thus, the annotation attribute contains the values contained within a @annotation feature value block, the ornaments attribute contains the values contained with a @ornaments feature value block and so forth. The CSSFontFeatureValuesMap interface uses the default map class methods but the set method has different behavior. It takes a sequence of unsigned integers and associates it with a given featureValueName. The method behaves the same as the default map class method except that a single unsigned long value is treated as a sequence of a single value. The method throws an exception if an invalid number of values is passed in. If the associated feature value block only allows a limited number of values, the set method throws an InvalidAccessError exception when the input sequence to set contains more than the limited number of values. See the description of multi-valued feature value definitions for details on the maximum number of values allowed for a given type of feature value block. The get method always returns a sequence of values, even if the sequence only contains a single value.

The CSSFontPaletteValuesRule interface

[Exposed=Window]
interface CSSFontPaletteValuesRule : CSSRule {
  readonly attribute CSSOMString name;
  readonly attribute CSSOMString fontFamily;
  readonly attribute CSSOMString basePalette;
  readonly attribute CSSOMString overrideColors;
};

The fontFamily and basePalette interfaces are parsed according to the appropriate CSS property syntax.

Serializing

Serializing font-related properties

Unless specifically noted for individual properties, the properties defined in this module follow the principles of [[cssom#serializing-css-values]]. parsing/font-variant-serialization.html

Serializing font-related at-rules

Unless specifically noted for individual descriptors, the descriptors defined for at-rules in this module follow the principles of [[cssom#serializing-css-values]]. In particular, following the principle of shorter representation: for descriptors which accept a range of values, if the start and end values are the same (the range is zero) the descriptor is serialized as a single value, not a range. variations/at-font-face-descriptors.html

For example, the rule

		@font-face {
			font-family: "foo";
			font-weight: 200 200;
		}
		

would serialize as

		@font-face {
			font-family: "foo";
			font-weight: 200;
		}
		

Also, following the principle of retaining only the last-defined value, as well as the principle of shortest representation, multiply-specified tuples and multiple blocks are serialized as a single block containing only the last-defined value.

For example, the declaration:

		/* Repeated declaration names, and multiple blocks of the same type*/
		@font-feature-values foo {
			@swash { pretty: 0; cool: 2; }
			@swash { pretty: 1; }
		}
	

would be serialized as:

    /* Canonical serialization */
    @font-feature-values foo {
        @swash { cool: 2; pretty: 1; }
    }
    

Appendix A: Mapping platform font properties to CSS properties

This appendix is included as background for some of the problems and situations that are described in other sections. It should be viewed as informative only. Font properties in CSS are designed to be independent of the underlying font formats used; they can be used to specify bitmap fonts, Type1 fonts, SVG fonts in addition to the common TrueType and OpenType fonts. But there are facets of the TrueType and OpenType formats that often cause confusion for authors and present challenges to implementers on different platforms. Originally developed at Apple, TrueType [[TRUETYPE]] was designed as an outline font format for both screen and print. Microsoft joined Apple in developing the TrueType format and both platforms have supported TrueType fonts since then. Font data in the TrueType format consists of a set of tables distinguished with common four-letter tag names, each containing a specific type of data. For example, naming information, including copyright and license information, is stored in the 'name' table. The character map ('cmap') table contains a mapping of character encodings to glyphs. Apple later added additional tables for supporting enhanced typographic functionality; these are now called Apple Advanced Typography, or AAT, fonts. Microsoft and Adobe developed a separate set of tables for advanced typography and called their format OpenType [[OPENTYPE]]. The OpenType specification is standardized at ISO as the Open Font Format [[OPEN-FONT-FORMAT]]. In many cases the font data used under Microsoft Windows or Linux is slightly different from the data used under Apple's Mac OS X because the TrueType format allowed for explicit variation across platforms. This includes font metrics, names and character map data. Specifically, font family name data is handled differently across platforms. For TrueType and OpenType fonts these names are contained in the 'name' table, in name records with name ID 1. Multiple names can be stored for different locales, but Microsoft recommends fonts always include at least a US English version of the name. On Windows, Microsoft made the decision for backwards compatibility to limit this family name to a maximum of four faces; for larger groupings the "preferred family" (name ID 16) or "WWS family" (name ID 21) can be used. Other platforms such as OSX don't have this limitation, so the family name is used to define all possible groupings. Other name table data provides names used to uniquely identify a specific face within a family. The full font name (name ID 4) and the Postscript name (name ID 6) describe a single face uniquely. For example, the bold face of the Gill Sans family has a fullname of "Gill Sans Bold" and a Postscript name of "GillSans-Bold". There can be multiple localized versions of the fullname for a given face, but the Postscript name is always a unique name made from a limited set of ASCII characters. On various platforms, different names are used to search for a font. For example, with the Windows GDI CreateIndirectFont API, either a family or fullname can be used to lookup a face, while on Mac OS X the CTFontCreateWithName API call is used to lookup a given face using the fullname and Postscript name. Under Linux, the fontconfig API allows fonts to be searched using any of these names. In situations where platform API's automatically substitute other font choices, it may be necessary to verify a returned font matches a given name. The weight of a given face can be determined via the usWeightClass field of the OS/2 table or inferred from the style name (name ID 2). Likewise, the width can be determined via the usWidthClass of the OS/2 table or inferred from the style name. For historical reasons related to synthetic bolding at weights 200 or lower with the Windows GDI API, font designers have sometimes skewed values in the OS/2 table to avoid these weights. Rendering complex scripts that use contextual shaping such as Thai, Arabic and Devanagari requires features present only in OpenType or AAT fonts. Currently, complex script rendering is supported on Windows and Linux using OpenType font features while both OpenType and AAT font features are used under Mac OS X.

Security Considerations

See items 9, 16 and 17 in the self-review questionnaire below.

Privacy Considerations

Following Self-Review Questionnaire: Security and Privacy, and using the [[#font-taxonomy]]:

What information might this feature expose to Web sites or other parties, and for what purposes is that exposure necessary?

This specification allows the use of Web Fonts, which are requested on demand but are not installed. In the case where the document or stylesheet has a different origin to the Web Font, this network request exposes information in the Referer header, which may be harvested by font providers. In addition to Web Fonts, this specification continues to allow the use of Installed Fonts (both Preinstalled Fonts and User-Installed Fonts) as introduced in CSS1. While Web Fonts have the advantage of consistency across platforms, Installed Fonts have the advantage of zero download time. In some cases, and particularly for poorly-supported or minority languages, Installed Fonts allow information to be displayed which could not otherwise be displayed because there is no freely licensable Web Font which supports that language or because the latency or download time would make it's use infeasible, particularly for languages with a large character repertoire, or on slow or metered connections. Note: The set of installed fonts available in the Font Matching Algorithm is explicitly undefined. The available set of fonts is used by trackers to fingerprint users and reduce their privacy. However, some installed fonts, even some user-installed fonts, are required to make languages readable. User Agents may choose to make all installed fonts available for language support and design integrity reasons, or may choose to make some fonts unavailable for privacy reasons. In addition, User Agents may have additional facilities for fine-tuning this balance, such as interfaces which prompt users to explicitly make certain requested fonts available or unavailable (perhaps on a per-site basis). Different User Agents, even running on the same Operating System, are expected to strike different balances here. In the case of user agents which perform rendering of local resources (such as an HTML and CSS to PDF renderer, or a Web-based wordprocessor) access to all Installed Fonts (both Preinstalled Fonts and User-Installed Fonts) is necessary to provide the expected functionality. An attacker may obtain fingerprinting information by querying the Installed Fonts. In contrast to older technologies (notably Adobe Flash, which provided a complete list of Installed Fonts and sent this information in HTTP headers) such probing must be done one font at a time, providing the font family name and then checking (either via script, or by using unicode-range to selectively download webfonts depending on whether the user has a font by a certain name that supports a certain character) whether the font was loaded. This takes time, and checking for more than a few hundred fonts introduces a noticeable delay in page rendering. For especially privacy-sensitive contexts, options would include never downloading any webfonts (at the risk that some characters may be rendered incorrectly, or not at all), or always downloading all webfonts whether needed or not (ignoring unicode-range, and potentially downloading vast quantities of unused fonts each time the page is viewed).

Is this specification exposing the minimum amount of information necessary to power the feature?

An emerging consensus is that a user agent must expose Preinstalled Fonts for correct functioning, but there is no consensus on exposing User-Installed Fonts. This specification allows a user agent to ignore User-Installed Fonts for the purpose of the Font Matching Algorithm. Several existing user agents already do this. The minimum amount varies by type of user and is currently being debated. There is a useful taxonomy of User-Installed Font users which has been slightly extended. A permissive amount of information exposes potentially more fingerprinting information; a restrictive amount of information reduces fingerprinting but also reduces functionality and in some cases, for minority languages, would break the Web completely for those users. The possibility of a configurable, per-user opt-in to exposing some or all User-Installed Fonts, or a per-origin opt-in, is being discussed. The possibility of a privacy budget, which would penalize or disable a malicious web page which tested a large number of fonts, but allow a harmless page which tested a much smaller number, has also been discussed. Some user agents expose a more restricted set of Preinstalled Fonts in their Private Browsing, Incognito, or Resist Fingerprinting modes, compared to their normal mode.

How does this specification deal with personal information or personally-identifiable information or information derived thereof?

Personal information is not exposed by this specification. Personally identifiable information may be exposed in some cases. For example, for someone in Japan, having conditionally-enabled Japanese fonts enumerable probably isn't a substantial fingerprinting vector. For someone in Europe who has a Japanese IME in the text input menu, they are.

How does this specification deal with sensitive information?

Fingerprinting on Installed Fonts may expose sensitive information in some cases. For example, persecuted minorities risk leaking sensitive information by exposing that they use fonts required for a persecuted minority language; either by requesting a Web Font from a third party service, or exposing Preinstalled Fonts or User-Installed Fonts associated with that language.

Does this specification introduce new state for an origin that persists across browsing sessions?

No. Specifically, Web Fonts must not be accessible in any other Document from the one which either is associated with the @font-face rule or owns the FontFaceSet. Other applications on the device must not be able to access Web Fonts. This avoids information leaking across origins. Similarly, font palette values must only be available to the documents that reference it. Using an author-defined color palette outside of the documents that reference it would constitute a security leak since the contents of one page would be able to affect other pages, something an attacker could use as an attack vector.

What information from the underlying platform, e.g. configuration data, is exposed by this specification to an origin?

The ''system-ui'' keyword exposes the operating system's default system UI font to fingerprinting mechanisms.

Does this specification allow an origin access to sensors on a user’s device

No.

What data does this specification expose to an origin? Please also document what data is identical to data exposed by other features, in the same or different contexts.

For third-party Web Fonts loaded via a stylesheet, the stylesheet origin may be exposed to the third party in the Referer header. In addition, careful pairing of unicode-range and distinct src urls allows the third-party to see which characters are used on a page, which is a privacy risk for large character repertoire scripts such as CJK. For third-party Web Fonts preloaded in the HTML, the document origin may be similarly exposed.

Does this specification enable new script execution/loading mechanisms?

No. Specifically, for SVG-in-OpenType color fonts, the SVG used for glyph definitions should not contain script elements, and any script elements that do occur will not be executed.

Does this specification allow an origin to access other devices?

No.

Does this specification allow an origin some measure of control over a user agent’s native UI?

There is some risk that an attacker can spoof a native UI feature by determining the Operating System and using native-looking fonts appropriate to that Operating System.

What temporary identifiers might this specification create or expose to the web?

None.

How does this specification distinguish between behavior in first-party and third-party contexts?

For font loads, user agents must use the potentially CORS-enabled fetch method defined by the [[!HTML]] specification for URLs defined within @font-face rules. When fetching, user agents must use "Anonymous" mode, set the referrer source to the stylesheet’s URL and set the origin to the URL of the containing document. Thus, fonts will typically not be loaded cross-origin unless authors specifically take steps to permit cross-origin loads.

How does this specification work in the context of a user agent’s Private Browsing or "incognito" mode?

The specification makes no distinction. Some user agents may expose a more restricted set of Installed Fonts in these modes.

Does this specification have a "Security Considerations" and "Privacy Considerations" section?

Yes.

Does this specification allow downgrading default security characteristics?

No.

What should this questionnaire have asked?

It should have asked whether a malicious payload could crash the application, or indeed the entire Operating System, or even cause remote code execution. This possibility does exist for suitably crafted fonts on some platforms when fonts are installed and rendered, and this has been exploited in the wild. In practice, user agents running on Operating Systems with this vulnerability use a font sanitizer to detect such malformed or malicious fonts and prevent their being used.

Accessibility Considerations

The use of fonts to provide a visual rendering of text should not, in general, impact accessibility. For example, people using a screen reader to render text to speech will not download fonts, and are unaffected by what those fonts would have contained. However, this assumes that the semantics conveyed by the font glyphs and the semantics conveyed by the characters are the same. Historically, this has not always been the case. For example, in the early days of the Web it was common to use fonts (such as "Symbol", though others were used) to make Latin letter have Greek glyphs; while this worked visually, it would not work with a screen reader and text was also hard to search or index because the mapping was font-specific. With the rise of Unicode, it is now standard practice to use Greek characters for Greek text, and for Greek glyphs in fonts to map to Greek characters. Sadly, but avoidably, this practice persists with badly designed icon fonts. For example, such a font might put a "printer" icon on the Latin letter "P". This practice scatters meaningless letters through the text, which negatively affects text searching and indexing, gives hard to understand rendering if the icon font does not load, and impedes screen readers. A well designed font must assign such icons to semantically meaningful characters. For example, the printer icon might be assigned to the string "printer" or to the Unicode character 🖨 U+1F5A8 (PRINTER).

Acknowledgments

The CSS Working group would like to thank: Peter Constable for assorted language fixes. Optical sizing image prepared by Nick Sherman. Special thanks to Tab Atkins Jr. for providing the text for the section on Font Rendering Controls as well as the section on the 'font-display!!descriptor' descriptor. Special thanks to Ilya Grigorik and David Kuettel for their help in developing these sections.

Changes

Changes from the 21 December 2021 Working Draft

• Added Web Platform Tests coverage
• 'font-palette' and '@font-palette-values' no longer at risk
• Allowed limited set of string-form format specifies, for Web compatibility
• Make feature-* features-* for consistency
• Changed initial value of font-variant-emoji from auto to normal, for consistency with other font-variant-* properties
• Added values from font-variant-emoji to font-variant shorthand
• Added canonical list of font-variant-* properties affected by font-variant shorthand
• Renamed "system font fallback" to "installed font fallback to avoid confusion with system font
• Updated property and descriptor values to use the range notation
• Fixed some examples which did not match the specification
• Clarified that color fonts are not enabled by default
• Added some more explanation to font-palette:light|dark
• Use last declaration of key/palette index in override-colors
• Removed currentColor from override-colors example
• Clarified that out of range palette indexes are ignored

Changes from the 29 July 2021 Working Draft

• Clarified that functions and relative lengths in palettes are evaluated within the root element's context
• Added new section, overall changes since CSS Fonts 3
• Added more font-palette-values examples
• Renamed technology to tech
• New 'math' value added to 'font-size'
• Security and Privacy are now separate sections
• Linked to OpenType, TrueType and Graphite table definitions
• Updated examples which had used "supports"
• Removed old "supports" from format in src descriptor, replaced with new technology production
• Moved font-technology & font-format to a new section
• Formalized fetching and resource timing reporting, applied to fetching fonts
• Removed the <string> values from override-color and base-palette
• Defined correct processing of conflicting override-colors
• Introduced concept of complete palettes
• Clearer description of override-colors
• Removed conflict between FONT_PALETTE_VALUES_RULE and VIEWPORT_RULE
• Defined context for resolving override-color colors, no longer per-element
• Allowed base-palette to reference dark and light palettes
• Changed properties in CSSFontPaletteValuesRule to be read-only
• The palette-identifier parses as a dashed-ident rather than custom-ident, for extensibility
• Renamed override-color descriptor to override-colors, because it accepts a list of colors
• Clarified that base-palette and override-color take non-negative integers
• Corrected grammar of the font shorthand property
• Several corrections to the IDL for CSSFontPaletteValuesRule
• Removed the "none" value from font-palette
• Clarified incremental requirement
• A few more examples
• Added incremental font technology to supports
• Reduced the critical angle for oblique font matching from 20deg to 11deg, per WG resolution
• Allowed font-display in @font-feature-values (the prose allowed it but the grammar did not)

Changes from the 17 November 2020 Working Draft

• Added Graphite reference
• Added font feature technology keywords opentype, aat, and graphite
• Removed scary wording about variable fonts being new and experimental
• Reference to CSS Fonts 3 in introduction is informative
• Differentiated COLRv1 from COLRv0
• Clarify well-designed vs badly-designed icon fonts in terms of Unicode codepoints
• Added Accessibility Considerations section
• Clarified that font-optical-sizing interacts with font-size-adjust
• Used consistent capitalization for "user agent"
• Clarified that font-stretch should serialize to a number/percentage, not a keyword
• Suggested heuristics for loading ''optional'' fonts
• Clarified repeated items in grammars
• Replaced obsolete “potentially CORS-enabled fetch” with reference to Fetch
• Added missing small-caps value to font-synthesis
• Be explicit about which properties apply to text
• Updated links
• Fixed typos, syntax errors

Changes from the 13 November 2019 Working Draft

• Clarified that JS-free probing of Unicode support of fonts is possible
• Clarified OpenType feature tags are 4 characters, trailing-space padded
• Added font metric override descriptors
• Added link to font features enabled by default
• Aligned with ebIDL specification (undefined, not void)
• Corrected cross-origin example to use http not https
• Clarified that font-range, per OpenType, is between 1 and 999
• (Privacy) added mention of unicode-range privacy exploit
• Clarified use of kern vs. vkrn
• Added font collection format, example of Font Collection
• Added CBDT color fonts
• Added Security & Privacy appendix
• Added palette examples, including dark mode
• Clarified colorspace of font palette entries
• Avoiding cross-site font leakage amde RFC-2119 MUST
• Clarified monochromatic fallback on color fonts
• Removed remaining references to min-font-size, max-font-size
• Clarified that color names are ASCII case insensitive
• Added the value none to font-palette
• Marked font-palette and @font-palette-values as at-risk
• Aligned value definition reference across all specs.
• Further clarified the behavior of 'optional'
• Clarified that not all generic font families have to map to a font
• Reorganized generic font family introduction
• Added some motivation for generic font families
• Added a note about the generic emoji family and character support
• Clarified that italic is not a fallback for oblique
• Added warning on too large x-height
• Added better example for 'font-size-adjust'
• Added example for ui-sans-serif
• Miscellaneous editorial improvements, typo fixes, broken link fixes and markup improvements

Changes from the 20 September 2018 Working Draft

• Add note encouraging UAs to also implement platform-specific names for standard font families
• Add ui-serif, ui-sans-serif, ui-monospace, and ui-rounded generic font families
• Remove font-variant @font-face descriptor per WG resolution
• Remove font-min-size and font-max-size per WG resolution
• Clarify that font-style 'normal' animates as 'oblique 0deg'
• Clarify why specifying incomplete color palettes for compound fonts is a bad idea
• Add explicit [Exposed=Window] on interfaces
• Use correct terms, Unicode emoji presentation sequence and Emoji Presentation Participating Code Points
• Clarify that each string in font-variation-settings is paired with a single number
• Remove stray titling-caps from definition of font-variant-numeric property
• Better introduction to color fonts
• Add basic multicolor example
• Clarify that font variation settings do no affect font selection of fallback fonts
• Clarify italic angle wrt direction of slnt axis
• Better define emoji and math generic font families
• Add font-size: xxx-large
• Link to CSS Values definition of ex units
• Add scientific inferiors example of font-feature-settings
• Clarify that letter-spacing disables optional ligatures
• Port font-feature-settings property from CSS Fonts 3
• Port font-variant shorthand property from CSS Fonts 3
• Port font-variant-east-asian property from CSS Fonts 3
• Port font-variant-numeric property from CSS Fonts 3
• Port font-variant-caps property from CSS Fonts 3
• Port font-variant-position property from CSS Fonts 3
• Port font-variant-ligatures property from CSS Fonts 3
• Port font-kerning property from CSS Fonts 3
• Update IDL of The CSSFontPaletteValuesRule interface
• Changed initial value of font property descriptors from normal to auto
• Update syntax for font-stretch in font matching section
• Update font style matching examples
• Clarify description of font palettes
• Stop claiming that 'ch' uses the first available font
• Assorted formatting and markup fixes, link fixes, removal of inline closed issues
• Linking to latest versions of normative references

Changes from the 10 April 2018 Working Draft

• Added unicode value to font-variant-emoji
• Removed the media entry from property descriptions
• Broke up font-synthesis into longhands, for future extensibility
• Added override-color descriptor for color palettes
• Defined feature-value-name for font-variant-alternates
• Clarified @font-face src parsing rules
• Allow named instances from variable fonts to be used
• Appendix A: Mapping platform font properties to CSS properties ported over from CSS Fonts 3
• Character handling issues ported over from CSS Fonts 3
• Cluster matching ported over from CSS Fonts 3
• Add new auto value for font-weight, font-style and font-stretch descriptors
• Clarified font-display descriptor value names
• Support named palette entries
• More details on Fang Song generic family
• Changed default angle of oblique fonts to 14deg.
• font-feature-values ported over from CSS Fonts 3
• Clarified handling of unknown or unsupported fragment identifiers
• Clarified that color records in font palettes are zero-indexed
• Consistently use the new generic font families
• Editorial cleanup, clarifying examples, markup improvements, linkfixes, updating to latest references, and so on

Changes from the 20 September 2018 CSS Fonts 3 Recommendation

This summarizes the changes in CSS Fonts 4, compared to CSS Fonts 3.

• Added font-display descriptor for @font-face
• Added @font-feature-values rule
• Added font variation properties, including font-optical-sizing and font-variation-settings
• Added color font support
• Defined feature-value-name for font-variant-alternates
• Added new auto value for font-weight, font-style and font-stretch descriptors
• Added ui-serif, ui-sans-serif, ui-monospace, and ui-rounded generic font families
• Added font-size: xxx-large
• Added font metric override descriptors
• Added some motivation for generic font families
• Added font feature technology keywords opentype, aat, and graphite
• Added math value to font-size