CSS Color Module Level 5

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Abstract

This module extends CSS Color [css-color-4] to add color modification functions.

CSS is a language for describing the rendering of structured documents (such as HTML and XML) on screen, on paper, etc.

Status of this document

This section describes the status of this document at the time of its publication. A list of current W3C publications and the latest revision of this technical report can be found in the W3C technical reports index at https://www.w3.org/TR/.

This document was published by the CSS Working Group as a Working Draft using the Recommendation track. Publication as a Working Draft does not imply endorsement by W3C and its Members.

This is a draft document and may be updated, replaced or obsoleted by other documents at any time. It is inappropriate to cite this document as other than work in progress.

Please send feedback by filing issues in GitHub (preferred), including the spec code “css-color” in the title, like this: “[css-color] …summary of comment…”. All issues and comments are archived. Alternately, feedback can be sent to the (archived) public mailing list www-style@w3.org.

This document is governed by the 2 November 2021 W3C Process Document.

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1. Introduction

This section is not normative.

Web developers, design tools and design system developers often use color functions to assist in scaling the design of their component color relations. With the increasing usage of design systems that support multiple platforms and multiple user preferences, like the increased capability of Dark Mode in UI, this becomes even more useful to not need to manually set color, and to instead have a single source from which schemes are calculated.

LC color picker
chloropleth map of the US

Above, a color picker operating in CIE LCH space. Here, a pair of colors are being used to define a color scale on the Chroma-Lightness plane (constant Hue). Below, the color scale in use on a chloropleth map.

Currently Sass, calc() on HSL values, or PostCSS is used to do this. However, preprocessors are unable to work on dynamically adjusted colors; all current solutions are restricted to the sRGB gamut and to the perceptual limitations of HSL (colors are bunched up in the color wheel, and two colors with visually different lightness, like yellow and blue, can have the same HSL lightness).

This module adds two new functions: color-mix(), color-contrast(), and extends existing ones with relative color syntax.

It also extends the color() function so that not only predefined colorspaces, but also custom colorspaces defined by ICC profiles (including calibrated CMYK) can be used in CSS.

It also adds device-cmyk, a representation of uncalibrated cmyk color.

2. Mixing colors: the color-mix() function

This function takes two <color> specifications and returns the result of mixing them, in a given <color-space>, by a specified amount.

color-mix() = color-mix( <color-interpolation-method> , [ <color> && <percentage [0,100]>? ]#{2})

Percentages are required to be in the range 0% to 100%. Negative percentages are specifically disallowed. The percentages are normalized as follows:

  1. Let p1 be the first percentage and p2 the second one.

  2. If both percentages are omitted, they each default to 50% (an equal mix of the two colors).

  3. Otherwise, if p2 is omitted, it becomes 100% - p1

  4. Otherwise, if p1 is omitted, it becomes 100% - p2

  5. If the percentages sum to zero, the function is invalid.

  6. Otherwise, if both are provided and add up to greater than 100%, they are scaled accordingly so that they add up to 100%.

  7. Otherwise, if both are provided and add up to less than 100%, the sum is saved as an alpha multiplier. They are then scaled accordingly so that they add up to 100%.

This means that p1 becomes p1 / (p1 + p2) and p2 becomes p2 / (p1 + p2).

These syntactic forms are thus all equivalent: 
color-mix(in lch, purple 50%, plum 50%)
color-mix(in lch, purple 50%, plum)
color-mix(in lch, purple, plum 50%)
color-mix(in lch, purple, plum)
color-mix(in lch, plum, purple)
color-mix(in lch, purple 80%, plum 80%)

All produce a 50-50 mix of purple and plum, in lch: lch(51.51% 52.21 325.8) which is rgb(68.51% 36.01% 68.29%).

However, this form is not the same, as the alpha is less than one:

color-mix(in lch, purple 30%, plum 30%)

This produces lch(51.51% 52.21 325.8 / 0.6) which is rgb(68.51% 36.01% 68.29% / 0.6).

After normalizing both percentages, the result is produced via the following algorithm:

  1. Both colors are converted to the specified <color-space>. If the specified color space has a smaller gamut than the one in which the color to be adjusted is specified, gamut mapping will occur.

  2. Colors are then interpolated in the specified color space, as described in CSS Color 4 § 13 Interpolation. If the specified color space is a cylindrical-polar-color space, then the <hue-interpolation-method> controls the interpolation of hue, as described in CSS Color 4 § 13.3 Hue interpolation. If no <hue-interpolation-method> is specified, it is as if shorter had been specified. If the specified colorspace is a rectangular-orthogonal-color space, then specifying a <hue-interpolation-method> is an error.

  3. If an alpha multiplier was produced during percentage normalization, the alpha component of the interpolated result is multiplied by the alpha multiplier.

The result of mixing is the color at the specified percentage along the progression of the second color to the first color.

Note: As a corrollary, a percentage of 0% just returns the other color converted to the specified color space, and a percentage of 100% returns the same color converted to the specified color space.

This example produces a mixture of 40% peru and 60% palegoldenrod. 
color-mix(in lch, peru 40%, palegoldenrod)

The mixing is done in lch() color space. Here is a top-down view, looking along the neutral L axis:

Mixtures of peru and palegoldenrod. Peru has a hue angle, measured from the positive a axis, of 63.677 degrees while palegoldenrod has a hue angle of 98.834 degrees. Peru has a chroma, or distance from the central neutral axis, of 54.011 while palegoldenrod has a chroma of 31.406. Mixtures lie along the curve. A 40%/60% mixture is shown.

The calculation is as follows:

This example produces the mixture of teal and olive, in lch color space, with each lch channel being 65% of the value for teal and 35% of the value for olive.

Note: interpolating on hue and chroma keeps the intermediate colors as saturated as the endpoint colors.

color-mix(in lch, teal 65%, olive);
Mixtures of teal and olive. Teal has a hue angle, measured from the positive a axis, of 196.4524 degrees while olive has a hue angle of 99.5746 degrees. Teal has a chroma, or distance from the central neutral axis, of 31.6903 while olive has a chroma of 56.8124. Mixtures lie along the dashed curve. A 65%/35% mixture is shown.

The calculation is as follows:

The choice of mixing colorspace can have a large effect on the end result.

This example is a 50% mix of white and black, in three different color spaces. 
color-mix(in lch, white, black);
color-mix(in xyz, white, black);
color-mix(in srgb, white, black);

The calculation is as follows:

The mix in LCH gives an L value of 50%, a perfect mid gray, exactly as expected (mixing in Lab would do the same, as the Lightness axis is the same in LCH and Lab).

The mix in XYZ gives a result that is too light; XYZ is linear-light but is not perceptually uniform. The mix in sRGB gives a result that is a bit too light; sRGB is neither perceptually uniform nor linear-light.

This example produces the mixture of the a red and a sky blue, in xyz color space, with the mixture being 75.23% of that of the red (and thus, 24.77% of that of the blue). 
color-mix(in xyz, rgb(82.02% 30.21% 35.02%) 75.23%, rgb(5.64% 55.94% 85.31%));

The calculation is as follows:

This example is a 50% mix of white and blue, in three different color spaces.

color-mix(in lch, white, blue);
color-mix(in oklch, white, blue);
color-mix(in srgb, white, blue);

The calcuation is as follows:

So far, all the color-mix() examples have used fully opaque colors. To simplify the examples, the premultilication and unpremultiplication steps were omitted because these would simply multiply by 1, and divide by 1, so the result would be unchanged.

In the general case, colors may have non-unity alpha components and thus the premultiply, interpolate, unpremultiply steps must not be omitted.

This example is 25% semi-opaque red and 75% semi-opaque green. mixed in sRGB. Both the correct (premultiplied) and incorrect (non-premultiplied) workings are shown. 
color-mix(in srgb, rgb(100% 0% 0% / 0.7) 25%, rgb(0% 100% 0% / 0.2));

The calcuation is as follows:

The incorrect calculation would be:

This is a huge difference; the ΔE2000 between the correct and incorrect results is 30.7!

When the percentage normalization generates an alpha multiplier, the calculation is the same except for an additional last step.

This example is similar to the previous one, 25% semi-opaque red and 75% semi-opaque green. mixed in sRGB.

However in this case the percentages are specified as 20% of the first color and 60% of the second. This adds to 80% so the alpha multiplier is 0.8.

The mix percentages are then scaled by a factor of 100/80:
20% * 100/80 = 25%
60% * 100/80 = 75%
giving the same final mix percentages as the previous example.

color-mix(in srgb, rgb(100% 0% 0% / 0.7) 20%, rgb(0% 100% 0% / 0.2) 60%);

The calcuation is as follows:

Note: do not multiply the interpolated alpha by the alpha multiplier and then use that to undo premultiplication. That would be correct if the mix percentages were not scaled to sum to 100%, but they are, so doing it this way would adjust the mixed color twice.

3. Selecting the most contrasting color: the color-contrast() function

This function takes, firstly, a single color (typically a background, but not necessarily), secondly, a list of two or more colors, and thirdly, an optional target luminance contrast [WCAG21].

For each color in the list, the CIE Luminance (Y) is calculated, relative to a D65 whitepoint.

For each pair of colors, the WCAG 2.1 contrast is calculated: contrast = (Yl + 0.05) / (Yd + 0.05) where Yd is the luminance of the darker color in the pair and Yl is the luminance of the lighter color. The factor 0.05 represents the luminance contribution of the viewing flare.

Suppose that the single color was 
color(display-p3 0.38 0.11 0.05)

while the first color in the list was

yellow

The calculation is as follows:

It then selects from that list the first color to meet or exceed the target contrast. If no target is specified, it selects the first color with the highest contrast to the single color.

The single color is separated from the list with the keyword vs and the target contrast, if present, is separated from the list with the keyword to.

color-contrast() = color-contrast( <color> vs <color>#{2,}  [ to [<number> | AA | AA-large | AAA | AAA-large]]? )

The keyword AA is equivalent to 4.5, AA-large is equivalent to 3, AAA is equivalent to 7, and AAA-large is equivalent to 4.5 .

color-contrast(wheat vs tan, sienna, var(--myAccent), #d2691e)

The calculation is as follows:

Suppose myAccent has the value #b22222:

The highest contrast ratio is 5.081 so var(--myAccent) wins 
color-contrast(wheat vs bisque, darkgoldenrod, olive, sienna, darkgreen, maroon to AA)

The calculation is as follows:

The first color in the list which meets the desired contrast ratio of 4.5 is darkgreen.

color-contrast(wheat vs bisque, darkgoldenrod, olive, sienna, darkgreen, maroon to 5.8)

The calculation is as follows:

The first color in the list which meets the desired contrast ratio of 5.8 is maroon.

The colors in the list (after the keyword vs) are tested sequentially, from left to right; a color is the temporary winner if it has the highest contrast of all those tested so far.

List traversal is terminated once the target contrast has been met or exceeded.

Once the end of the list is reached, if there is no target contrast, the current temporary winner is the overall winner. Thus, if two colors in the list happen to have the same contrast, the earlier in the list wins because the later one has the same contrast, not higher.

If there is a target contrast, and the end of the list is reached without meeting that target, either white or black is returned, whichever has the higher contrast.

color-contrast(wheat vs bisque, darkgoldenrod, olive to AA)

The calculation is as follows:

No color in the list meets the desired contrast ratio of 4.5, so black is returned as the contrast (15.982) is higher than that of white (1.314).

foo {
  --bg: hsl(200 50% 80%);
  --purple-in-hsl: hsl(300 100% 25%);
  color: color-contrast(var(--bg) vs hsl(200 83% 23%), purple, var(--purple-in-hsl));
  }

The calculation is as follows:

The calculated values here are shown to six significant figures, to demonstrate that early rounding to a lower precision would have given the wrong result (0.061575 is very close to 0.061487; 6.08409 is very close to 6.08889).

4. Relative color syntax

In previous levels of this specification, the color functions could only specify colors in an absolute manner, by directly specifying all of the color channels.

The new relative color syntax allows existing colors to be modified using the color functions: if an origin color is specified, then each color channel can either be directly specified, or taken from the origin color (and possibly modified with math functions).

The precise details of each function’s changes to accomodate relative colors are listed below, but they all follow a common structure:

If the origin color was originally specified with a different color function, it’s first converted into the chosen color function, so it has meaningful values for the channels.

For example, if a theme color is specified as opaque, but in a particular instance you need it to be partially transparent: 
html { --bg-color: blue; }
.overlay {
  background: rgb(from var(--bg-color) r g b / 80%);
}

In this example, the r, g, and b channels of the origin color are unchanged, indicated by specifying them with the keywords drawing their values from the origin color, but the opacity is set to 80% to make it slightly transparent, regardless of what the origin color’s opacity was.

By using the channel keywords in a math function, an origin color can be manipulated in more advanced ways. 
html { --color: green; }
.foo {
  --darker-accent: lch(from var(--color) calc(l / 2) c h);
}

In this example, the origin color is darkened by cutting its lightness in half, without changing any other aspect of the color.

Note as well that the origin color is a color keyword (effectively RGB), but it’s automatically interpreted as an LCH color due to being used in the lch() function.

While most uses of relative color syntax will use the channel keywords in their corresponding argument, you can use them in any position.

For example, to do a rough approximation of grayscaling a color:

--blue-into-gray: rgb(from var(--color)
                    calc(r * .3 + g * .59 + b * .11)
                    calc(r * .3 + g * .59 + b * .11)
                    calc(r * .3 + g * .59 + b * .11));

Using this, red would become rgb(30% 30% 30%), lime would become rgb(59% 59% 59%), and blue would become rgb(11% 11% 11%). A more moderate color, like darkolivegreen, which has RGB values rgb(85 107 47), would become approximately rgb(37% 37% 37%).

(Rough because firstly, although this looks like a luminance calculation, the red green and blue values are manipulated in gamma-encoded space rather than linear-light; secondly, the weighting factors are those for the obsolete NTSC color space, not sRGB.)

(Note, though, that an easier and more accurate way to grayscale a color is to use the lch() function, as that color space is more accurate to human perception: lch(from var(--color) l 0 h) preserves the lightness, but zeroes out the chroma, which determines how "colorful" the color is.)

4.1. Relative RGB colors

The grammar of the rgb() function is extended as follows:

rgb() = rgb( [<percentage> | none]{3} [ / [<alpha-value> | none] ]? ) |
        rgb( [<number> | none]{3} [ / [<alpha-value> | none] ]?
        rgb( [ from <color> ]? [ <number> | <percentage> | none]{3} [ / <alpha-value> ]?  )
<alpha-value> = <number> | <percentage>

Within a relative color syntax rgb() function, the allowed channel keywords are:

To manipulate color channels in the sRGB color space: 
rgb(from  indianred 255 g b)

This takes the sRGB value of indianred (205 92 92) and replaces the red channel with 255 to give rgb(255 92 92).

4.2. Relative HSL colors

The grammar of the hsl() function is extended as follows:

hsl() = hsl(([from <color>]?
        [<hue> | none] [<percentage> | none] [<percentage> | none]
        [ / [<alpha-value> | none] ]? )

Within a relative color syntax hsl() function, the allowed channel keywords are:

This adds 180 degrees to the hue angle, giving a complementary color. 
--accent:  lightseagreen;
--complement:   hsl(from var(--accent) calc(h + 180deg) s l);

lightseagreen is hsl(177deg 70% 41%), so --complement is hsl(357deg 70% 41%)

4.3. Relative HWB colors

The grammar of the hwb() function is extended as follows:

hwb() = hwb([from <color>]?
        [<hue> | none] [<percentage> | none] [<percentage> | none]
        [ / [<alpha-value> | none] ]? )

Within a relative color syntax hwb() function, the allowed channel keywords are:

4.4. Relative Lab colors

The grammar of the lab() function is extended as follows:

lab() = lab([from <color>]?
        [<percentage> | none] [<number> | none] [<number> | none]
        [ / [<alpha-value> | none] ]? )

Within a relative color syntax lab() function, the allowed channel keywords are:

Multiple ways to adjust the transparency of a base color:

Note that all the adjustments are lossless in the sense that no gamut clipping occurs, since lab() encompasses all visible color. This is not true for the alpha adjustments in the sRGB based functions (such as 'rgb()', 'hsl()', or 'hwb()'), which would also convert to sRGB in addition to adjusting the alpha transparency.

Fully desaturating a color to gray, keeping the exact same lightness: 
--mycolor:  orchid;
// orchid is lab(62.753% 52.460 -34.103)
--mygray:  lab(from var(--mycolor) l 0 0)
// mygray is lab(62.753% 0 0) which is rgb(59.515% 59.515% 59.515%)

4.5. Relative OKLab colors

The grammar of the oklab() function is extended as follows:

oklab() = oklab([from <color>]?
          [<percentage> | none] [<number> | none] [<number> | none]
          [ / [<alpha-value> | none] ]? )

Within a relative color syntax oklab() function, the allowed channel keywords are:

4.6. Relative LCH colors

The grammar of the lch() function is extended as follows:

lch() = lch([from <color>]?
        [<percentage> | none] [<number> | none] [<hue> | none]
        [ / [<alpha-value> | none] ]? )

Within a relative color syntax lch() function, the allowed channel keywords are:

lch(from peru calc(l * 0.8) c h) produces a color that is 20% darker than peru or lch(62.2532% 54.0114 63.6769), with its chroma and hue left unchanged. The result is lch(49.80256% 54.0114 63.6769)
This adds 180 degrees to the hue angle, giving the complementary color. 
--accent:  lightseagreen;
--complement:   LCH(from var(--accent) l c calc(h + 180deg));

lightseagreen is LCH(65.4937% 39.4484 190.1013), so --complement is LCH(65.4937% 39.4484 370.1013)

Fully desaturating a color to gray, keeping the exact same lightness: 
--mycolor:  orchid;
// orchid is lch(62.753% 62.571 326.973)
--mygray:  lch(from var(--mycolor) l 0 h)
// mygray is lch(62.753% 0 326.973) which is rgb(59.515% 59.515% 59.515%)

But now (since the hue was preserved) re-saturating again

--mymuted:  lch(from var(--mygray) l 30 h);
// mymuted is lch(62.753% 30 326.973) which is rgb(72.710% 53.293% 71.224%)

However, unlike HSL, manipulations are not guaranteed to be in-gamut.

In this example, the aim is to produce a new color with the same Lightness and Chroma, but the triad (hue differs by 120 degrees). The origin color is inside the RGB gamut, but rotating the hue in LCH produces an out of gamut color. 
--mycolor:  lch(60% 90 320);
lch(from var(--mycolor) l c calc(h - 120));

This gives a very high-chroma blue-green, lch(60% 90 200) which is color(srgb -0.6 0.698 0.772) and thus out of gamut (negative red value) for sRGB. Indeed, it is out of gamut for display-p3: color(display-p3 -0.46 0.68 0.758) and even rec2020: color(rec2020 -0.14 0.623 0.729).

The closest color inside the sRGB gamut would be lch(60.71% 37.56 201.1) which is rgb(0% 64.2% 66.3%). The difference in chroma (37.5, instead of 90) is huge.

Diagram of CH plane showing relative color manipulation
This diagram shows the sRGB gamut, in the CIE ab plane. Small circles indicate the primary and secondary color. The origin color, shown as a large circle, is in gamut for sRGB; becomes out of gamut (shown as a grey fill and red border) when the LCH hue is rotated -120°. The gamut-mapped result has much lower chroma.

Performing the same operation in HSL will return an in-gamut result. But it is unsatisfactory in other ways:

--mycolor:  lch(60% 90 320);
hsl(from var(--mycolor) calc(h - 120) s l);

In HSL, --mycolor is hsl(289.18 93.136% 65.531%) so subtracting 120 degrees gives hsl(169.18 93.136% 65.531%). Converting that result back to LCH lch(89.0345% 49.3503 178.714) we see that, due to the hue rotate in HSL, Lightness shot up from 60% to 89%, the Chroma has dropped from 90 to 49, and the Hue actually changed by 141 degrees not 120.

4.7. Relative OKLCH colors

The grammar of the oklch() function is extended as follows:

oklch() = oklch([from <color>]?
          [<percentage> | none] [<number> | none] [<hue> | none]
          [ / [<alpha-value> | none] ]? )

Within a relative color syntax oklch() function, the allowed channel keywords are:

In this example, the aim is again to produce a new color with the same Lightness and Chroma, but the triad (hue differs by 120 degrees). In this example, we will do the manipulation in OKLCH. The origin color is inside the RGB gamut, but rotating the hue in OKLCH again produces an out of gamut color. 
--mycolor:  lch(60% 90 320);
oklch(from var(--mycolor) l c calc(h - 120));

--mycolor is oklch(69.012% 0.25077 319.893). Subtracting 120 from the Hue gives a very high-chroma blue-green, oklch(69.012% 0.25077 199.893) which is out of sRGB gamut, color(srgb -0.6018 0.7621 0.8448) as the negative red component indicates. Bring this into gamut by reducing OKLCH Chroma, yeilds oklch(69.012% 0.1173 199.893). The OKLCH chroma has dropped from 0.251 to 0.117.

5. Specifying custom color spaces: the color() function

The color() function allows a color to be specified in a particular, specified color space (rather than the implicit sRGB color space that most of the other color functions operate in).

In this level the color() function is extended to allow custom color spaces, in addition to the predefined spaces from CSS Color 4 § 10.2 Predefined color spaces: srgb, display-p3, a98-rgb, prophoto-rgb, rec2020, and xyz..

It is also extended to allow relative, rather than just absolute, colors.

Its syntax is extended as follows:

color() = color( [from <color>]? <colorspace-params> [ / <alpha-value> ]? )
colorspace-params = [<custom-params> | <predefined-rgb-params> | <xyz-params>]
custom-params = <dashed-ident> [ <number> | <percentage> | none ]#
predefined-rgb-params = <predefined-rgb> [ <number> | <percentage> | none ]{3}
predefined-rgb = srgb | srgb-linear | display-p3 | a98-rgb | prophoto-rgb | rec2020
xyz-params = <xyz> [ <number> | none ]{3}
xyz = xyz | xyz-d50 | xyz-d65

The color function takes parameters specifying a color, in an explicitly listed color space.

It represents either an invalid color, as described below, or a valid color.

Any color which is not an invalid color is a valid color.

A color may be a valid color but still be outside the range of colors that can be produced by an output device (a screen, projector, or printer). It is said to be out of gamut for that color space.

An out of gamut color has component values less than 0 or 0%, or greater than 1 or 100%. These are not invalid; instead, for display, they are gamut-mapped using a relative colorimetric intent which brings the values within the range 0/0% to 1/100% at computed-value time.

Each valid color is either in-gamut for the output device (screen, or printer), or it is out of gamut.

5.1. Relative color-function colors

Within a relative color syntax color() function using <custom-params>, the number and name of the allowed channel keywords are:

Within a relative color syntax color() function using <predefined-rgb-params>, the allowed channel keywords are:

Within a relative color syntax color() function using <xyz-params>, the allowed channel keywords are:

5.2. Custom color spaces

CSS allows colors to be specified by reference to a color profile. This could be for example a calibrated CMYK printer, or an RGB color space, or any other color or monochrome output device which has been characterized.

This example specifies four calibrated colors: two are custom spaces (for a SWOP-coated CMYK press, and for a wide-gamut seven-ink printer), the other two are predefined spaces (the ProPhoto RGB, and display-p3 RGB spaces). In each case, the numerical parameters are in the range 0.0 to 1.0 (rather than, for example, 0 to 255). 
color: color(--swopc 0.0134 0.8078 0.7451 0.3019);
color: color(--indigo 0.0941 0.6274 0.3372 0.1647 0 0.0706 0.1216);
color: color(prophoto-rgb 0.9137 0.5882 0.4784);
color: color(display-p3 0.3804 0.9921 0.1412);

The colors not using a predefined color space CSS Color 4 § 10.2 Predefined color spaces: srgb, display-p3, a98-rgb, prophoto-rgb, rec2020, and xyz. are distinguished by their use of <dashed-ident> and also need a matching @color-profile at-rule somewhere in the stylesheet, to connect the name with the profile data.

@color-profile --swopc {
  src: url('http://example.org/swop-coated.icc');}
@color-profile --indigo {
  src: url('http://example.org/indigo-seven.icc');}

5.3. Specifying a color profile: the @color-profile at-rule

The @color-profile rule defines and names a color profile which can later be used in the color() function to specify a color.

It’s defined as:

@color-profile = @color-profile [<dashed-ident> | device-cmyk] { <declaration-list> }

The <dashed-ident> gives the color profile’s name, by which it will be used in a CSS stylesheet. Alternatively, the device-cmyk keyword means that this color profile will, if valid, be used to resolve colors specified in device-cmyk.

The @color-profile rule accepts the descriptors defined in this specification.

Name: src
For: @color-profile
Value: <url>
Initial: n/a

The src descriptor specifies the URL to retrieve the color-profile information from.

The retrieved ICC profile is valid if

If the profile is not valid, all CSS colors which reference this profile are invalid colors.

To fetch an external color profile, given a @color-profile rule rule, fetch a style resource given rule’s URL, with stylesheet being rule’s parent CSS style sheet, destination "color-profile", CORS mode "cors", and processResponse being the following steps given response res and null, failure or a byte stream byteStream: If byteStream is a byte stream, apply the color profile as parsed from |byteStream.

Note: The Internet Media Type ("MIME type") for ICC profiles is application/vnd.iccprofile.

Name: rendering-intent
For: @color-profile
Value: relative-colorimetric | absolute-colorimetric | perceptual | saturation
Initial: relative-colorimetric

Color profiles contain “rendering intents”, which define how to gamut-map their color to smaller gamuts than they’re defined over. Often a profile will contain only a single intent, but when there are multiple, the rendering-intent descriptor chooses one of them to use.

The four possible rendering intents are [ICC]:

relative-colorimetric
Media-relative colorimetric is required to leave source colors that fall inside the destination medium gamut unchanged relative to the respective media white points. Source colors that are out of the destination medium gamut are mapped to colors on the gamut boundary using a variety of different methods.

The media-relative colorimetric rendering intent is often used with black point compensation, where the source medium black point is mapped to the destination medium black point as well. This method must map the source white point to the destination white point. If black point compensation is in use, the source black point must also be mapped to the destination black point. Adaptation algorithms should be used to adjust for the change in white point. Relative relationships of colors inside both source and destination gamuts should be preserved. Relative relationships of colors outside the destination gamut may be changed.

absolute-colorimetric
ICC-absolute colorimetric is required to leave source colors that fall inside the destination medium gamut unchanged relative to the adopted white (a perfect reflecting diffuser). Source colors that are out of the destination medium gamut are mapped to colors on the gamut boundary using a variety of different methods. This method produces the most accurate color matching of in-gamut colors, but will result in highlight clipping if the destination medium white point is lower than the source medium white point. For this reason it is recommended for use only in applications that need exact color matching and where highlight clipping is not a concern.

This method MUST disable white point matching and black point matching when converting colors. In general, this option is not recommended except for testing purposes.

perceptual
This method is often the preferred choice for images, especially when there are substantial differences between the source and destination (such as a screen display image reproduced on a reflection print). It takes the colors of the source image and re-optimizes the appearance for the destination medium using proprietary methods. This re-optimization may result in colors within both the source and destination gamuts being changed, although perceptual transforms are supposed to maintain the basic artistic intent of the original in the reproduction. They will not attempt to correct errors in the source image.

Note: With v2 ICC profiles there is no specified perceptual reference medium, which can cause interoperability problems. When v2 ICC profiles are used it can be safer to use the media-relative colorimetric rendering intent with black point compensation, instead of the perceptual rendering intent, unless the specific source and destination profiles to be used have been checked to ensure the combination produces the desired result.

This method should maintain relative color values among the pixels as they are mapped to the target device gamut. This method may change pixel values that were originally within the target device gamut, in order to avoid hue shifts and discontinuities and to preserve as much as possible the overall appearance of the scene.

saturation
This option was created to preserve the relative saturation (chroma) of the original, and to keep solid colors pure. However, it experienced interoperability problems like the perceptual intent, and as solid color preservation is not amenable to a reference medium solution using v4 profiles does not solve the problem. Use of this rendering intent is not recommended unless the specific source and destination profiles to be used have been checked to ensure the combination produces the desired result. This option should preserve the relative saturation (chroma) values of the original pixels. Out of gamut colors should be converted to colors that have the same saturation but fall just inside the gamut.
Name: components
For: @color-profile
Value: <ident>#
Initial: n/a

Color profiles can define color spaces which contain a varying number of components. For example, a Cyan, Magenta, Yellow and Black (CMYK) profile has four components named c, m, y and k While a four-component additive screen profile might use four components named r, g, y and b.

The value of this descriptor is a comma-separated list of <ident> tokens. Each <ident>> names a component, in the order in which they are used in the color profile, while the total number of tokens defines the number of components.

A component must not be named none, because that would clash with the token for missing values. If this descriptor contains a component called none, the descriptor is invalid.

This descriptor declares that there are four components named cyan, magenta, yellow and black: 
components: cyan, magenta, yellow, black

while this descriptor opts for terser names:

components: c,m,y,k
This descriptor declares that there are seven components named cyan, magenta, yellow, black, orange, green and violet: 
components: cyan, magenta, yellow, black, orange, green, violet

5.4. CSS and print: using calibrated CMYK and other printed color spaces

The @color-profile at-rule is not restricted to RGB color spaces. While screens typically display colors directly in RGB, printers often represent colors with CMYK.

Calibrated four color print with Cyan, Magenta, Yellow and Black (CMYK), or high-fidelity wide gamut printing with additional inks such as Cyan Magenta Yellow Black Orange Green Violet (CMYKOGV) can also be done in CSS, provided you have an ICC profile corresponding to the combination of inks, paper, total ink coverage and equipment you will use.

For example, using offset printing to ISO 12647-2:2004 / Amd 1:2007 using the FOGRA39 characterization data on 115gsm coated paper with an ink limit of 300% Total Area Coverage. 
@color-profile --fogra39 {
  src: url('https://example.org/Coated_Fogra39L_VIGC_300.icc');
}
.header {
  background-color:   color(--fogra39 0% 70% 20% 0%);
  }

Here the color() function first states the name we have given the profile, then gives the percentage of cyan, magenta, yellow, and black.

In this profile, this resolves to the color  lab(63.673303% 51.576902 5.811058) which is  rgb(93.124, 44.098% 57.491%).

Because the actual color resulting from a given CMYK combination is known, an on-screen visualization of the printed output (soft-proof) can be made.

Also, procedures that rely on knowing the color (anti-aliasing, compositing, using the color in a gradient, etc) can proceed as normal.

A color checker, used for ensuring color fidelity in the print and photographic industries. Averaged measured Lab values are available for each patch. The rectangles show the Lab values, converted to sRGB. The circles, which are barely visible, show the Lab values, passed through a FOGRA51 ICC profile to convert them to CMYK. The CMYK values are then passed through the same ICC profile in reverse, to yield new Lab values. These are then converted to sRGB for display.

The one patch with a more visible circle (third row, first patch) is because the color is slightly outside the gamut of the FOGRA51 CMYK space used.

The table below shows, for each patch, the DeltaE 2000 between the original Lab and the Lab value after round-tripping through CMYK. A DeltaE 2000 of 1 or more is just visible.

0.06 0.07 0.03 0.04 0.06 0.17
0.03 0.75 0.05 0.06 0.03 0.02
1.9 0.04 0.06 0.05 0.02 0.05
0.03 0.08 0.03 0.03 0.04 0.80
This example is using offset printing to ISO 12647-2:2004 using the CGATS/SWOP TR005 2007 characterization data on grade 5 paper with an ink limit of 300% Total Area Coverage, and medium gray component replacement (GCR). 
@color-profile --swop5c {
  src: url('https://example.org/SWOP2006_Coated5v2.icc');
}
.header {
  background-color:   color(--swop5c 0% 70% 20% 0%);
}

In this profile, this amount of CMYK (the same percentages as the previous example) resolves to the color  lab(64.965217% 52.119710 5.406966) which is  rgb(94.903% 45.248% 59.104%).

Fallback colors can be specified, for example using media queries, to be used if the specified CMYK color is known to be outside the sRGB gamut.

This example uses the same FOGRA39 setup as before, but specifies a bright green which is outside the sRGB gamut. It is, however, inside the display-p3 gamut. Therefore it is displayed as-is on wide gamut screens and in print, and a less intense fallback color is used on sRGB screens. 
@media (color-gamut: srgb) {
  .header {
    background-color:  rgb(8.154% 60.9704% 37.184%);
    }
}
@media print, (color-gamut: p3){
  .header {
    background-color:  color(--fogra39 90% 0% 90% 0%);
    }
}

This example does not use illustrative swatches, because most of the colors are outside of sRGB.

This CMYK color corresponds to lab(56.596645% -58.995875 28.072154) or lch(56.596645% 65.33421077211648 154.5533771086801). In sRGB this would be rgb(-60.568% 62.558% 32.390%) which, as the large negative red component shows, is out of gamut.

Reducing the chroma until the result is in gamut gives lch(56.596645% 51 154.5533771086801) which is rgb(8.154% 60.9704% 37.184%) and this has been manually specified as a fallback color.

For wide gamut screens, the color is inside the display-p3 gamut (it is display-p3(0.1658 0.6147 0.3533) ).

Colors are not restricted to four inks (CMYK). For example, wide-gamut 7 Color ink sets can be used.

This example uses the beta FOGRA55 dataset for KCMYOGV seven-color printing. Four of the inks - black, cyan, magenta, and yellow - are the same as, and give the same results as, the FOGRA51 set. The other three inks are:

The measurement condition is M1, which means that optical brighteners in the paper are accounted for and the spectrophotometer has no UV-cut filter.

@color-profile --fogra55beta {
  src: url('https://example.org/2020_13.003_FOGRA55beta_CL_Profile.icc');
}
.dark_skin {
  background-color: 
  color(--fogra55beta 0.183596 0.464444 0.461729 0.612490 0.156903 0.000000 0.000000);
}
.light_skin {
  background-color: 
  color(--fogra55beta 0.070804 0.334971 0.321802 0.215606 0.103107 0.000000 0.000000);
}
.blue_sky {
  background-color: 
  color(--fogra55beta 0.572088 0.229346 0.081708 0.282044 0.000000 0.000000 0.168260);
}
.foliage {
  background-color: 
  color(--fogra55beta 0.314566 0.145687 0.661941 0.582879 0.000000 0.234362 0.000000);
}
.blue_flower {
  background-color: 
  color(--fogra55beta 0.375515 0.259934 0.034849 0.107161 0.000000 0.000000 0.308200);
}
.bluish_green {
  background-color: 
  color(--fogra55beta 0.397575 0.010047 0.223682 0.031140 0.000000 0.317066 0.000000);
}

5.5. Converting CMYK colors to Lab

Conversion from a calibrated CMYK color space to Lab is typically done by looking up the Lab values in an ICC profile.

5.6. Converting Lab colors to CMYK

For print, Lab colors will need to be converted to the color space of the printer.

This is typically done by looking up the CMYK values in an ICC profile.

6. Uncalibrated CMYK Colors: the device-cmyk() function

Sometimes, when a given printer has not been calibrated, but the output for particular ink combinations is known through experimentation, or via a printed sample swatchbook, it is useful to express CMYK colors in a device-dependent way.

Note: Because the actual resulting color can be unknown, CSS processors might attempt to approximate it. This approximation is likely to be visually very far from the actual printed result.

The device-cmyk() function allows authors to specify a color in this way:

device-cmyk() = device-cmyk( <cmyk-component>{4} [ / <alpha-value> ]? )
<cmyk-component> = <number> | <percentage>

The arguments of the device-cmyk() function specify the cyan, magenta, yellow, and black components, in order, as a number between 0 and 1 or a percentage between 0% and 100%. These two usages are equivalent, and map to each other linearly. Values less than 0 or 0%, or greater than 1 or 100%, are not invalid; instead, they are clamped to 0/0% or 1/100% at computed-value time.

The fifth argument specifies the alpha channel of the color. It’s interpreted identically to the fourth argument of the rgb() function. If omitted, it defaults to 100%.

Typically, print-based applications will actually store the used colors as CMYK, and send them to the printer in that form. However, such colors do not have a colorimetric interpretation, and thus cannot be used in gradients, compositing, blending and so on.

As such, Device CMYK colors must be converted to an equivalent color. This is not trivial, like the conversion from HSL or HWB to RGB; the precise conversion depends on the precise characteristics of the output device.

  1. If the user, author, or user-agent stylesheet has an @color-profile definition for device-cmyk, and the resource specified by the src descriptor can be retrieved, and the resource is a valid CMYK ICC profile, and the user agent can process ICC profiles, the computed value of the device-cmyk() function must be the Lab value of the CMYK color.
  2. Otherwise, the computed value of the device-cmyk() function must be the sRGB value of the CMYK color, as converted with the following naive conversion algorithm.
For example, with no @color-profile, the following colors are equivalent, using the naive conversion. 
color:  device-cmyk(0 81% 81% 30%);
color:  rgb(178 34 34);
color:  firebrick;
With the @color-profile specified as in the example stylesheet, the following colors are equivalent, using colorimetric conversion. 
color:  device-cmyk(0 81% 81% 30%);
color:  lab(45.060% 45.477 35.459)
color:  rgb(70.690% 26.851% 19.724%);

The naive conversion is necessarily approximate, since it has no knowledge of the colorimetry of the inks, the dot gain, the colorimetry of the RGB space, and so on.

A color checker, used for ensuring color fidelity in the print and photographic industries. Averaged measured Lab values are available for each patch. The rectangles show the Lab values, converted to sRGB. The circles show the Lab values, passed through an ICC profile to convert them to CMYK. The CMYK value are then naively converted to sRGB.

The table below shows, for each patch, the DeltaE 2000 between the original Lab and the Lab value after round-tripping through CMYK. A DeltaE 2000 of 1 or more is just visible, while 5 or more is just a different color altogether.

11.33 9.36 5.66 7.52 12.39 21.58
6.40 8.79 11.77 17.16 11.91 3.97
12.1 17.00 3.38 1.94 18.08 14.97
1.89 6.56 7.85 8.76 9.82 10.29

6.1. Naively Converting Between Uncalibrated CMYK and sRGB-Based Colors

To naively convert from CMYK to RGBA:

To naively convert from RGBA to CMYK:

7. Resolving <color> Values

7.1. Resolving color-contrast() values

The computed value is the specified color-contrast() function with each <color> parameter resolved according to CSS Color 4 § 4.6 Resolving <color> Values, and the keywords AA, AA-large, AAA, AAA-large replaced with their corresponding numeric value.

The used value is the winning color resolved according to CSS Color 4 § 4.6 Resolving <color> Values.

For example, given a current color value of rgb(179 213 230), the value

color-contrast(currentColor vs hsl(200 83% 23%), purple to AA)

has the computed value

color-contrast(currentColor vs rgb(10 75 107), rgb(128 0 128) to 4.5)

and the used value

rgb(128 0 128)

7.2. Resolving device-cmyk values

The computed and used value is the specified device-specific CMYK color, (with components as <number>, not <percentage>) paired with the specified alpha channel (as a <number>, not a <percentage>; and defaulting to opaque if unspecified).

The actual value can vary based on the operation; for rendering to a CMYK-capable device, it may be rendered as a CMYK color; for blending with non-CMYK colors or rendering to a non-CMYK device, it must be converted as specified in § 6 Uncalibrated CMYK Colors: the device-cmyk() function.

For example, 
 device-cmyk(0% 70% 20% 0%)

has the specified and actual value

 device-cmyk(0 0.7 0.2 0)

and will, if the implementation understands ICC profiles and has an appropriate profile installed, have the used value

 lab(63.673% 51.577 5.811)

Note: As with all colors, the used value is not available to script.

8. Serialization

This section extends CSS Color 4 § 4.7 Serializing <color> Values to add serialization of the results of the color-mix(), color-contrast(), and relative color functions.

In this section, the strings used in the specification and the corresponding characters are as follows.

String Character
" " U+0020 SPACE
"," U+002C COMMA
"-" U+002D HYPHEN-MINUS
"." U+002E FULL STOP
"/" U+002F SOLIDUS

The string "." shall be used as a decimal separator, regardless of locale, and there shall be no thousands separator.

As usual, if the alpha of the result is exactly 1, it is omitted from the serialization; an implicit value of 1 (fully opaque) is the default.

8.1. Serializing color-mix()

The serialization of the result of a color-mix() function is a <color>, as defined in CSS Color 4 § 4.7 Serializing <color> Values. The form used depends on the color space specified with "in".

The minimum precision for round-tripping is the same as that specified in CSS Color 4 § 4.7 Serializing <color> Values.

mixing color space form
srgb color(srgb r g b)
srgb-linear color(srgb-linear r g b)
hsl hsl(h s l) ¹
hwb hwb(h w b) ²
xyz-d65 color(xyz-d65 x y z)
xyz-d50 color(xyz-d50 x y z)
xyz color(xyz-d65 x y z) ³
lab lab(l a b)
lch lch(l c h)
oklab oklab(l a b)
oklch oklch(l c h)
¹
hsl() will then serialize as rgb() or rgba()
²
hwb() will then serialize as rgb() or rgba()
³
Because xyz is just an alias for xyz-d65
The result of this color mixture 
color-mix(in lch, peru 40%, palegoldenrod)

is serialized as the string "lch(79.7256% 40.448 84.771)" while the result of

color-mix(in srgb, peru 40%, palegoldenrod)

is serialized as the string "color(srgb 0.8816 0.7545 0.4988)".

8.2. Serializing color-contrast()

The serialization of the result of a color-contrast() function is a <color>, as defined in CSS Color 4 § 4.7 Serializing <color> Values. The form used is the same as that used to specify the winning color.

The minimum precision for round-tripping is the same as that specified in CSS Color 4 § 4.7 Serializing <color> Values.

The winner of this contrast choice 
color-contrast(wheat vs olive, sienna, maroon)

is maroon, so the result is serialized as "rgb(128 0 0)".

While the winner of

color-contrast(wheat vs color(prophoto-rgb 0.4 0.4 0.2), color(display-p3 0.45 0.08 0.05))

is color(display-p3 0.45 0.08 0.05), so the result is serialized as "color(display-p3 0.45 0.08 0.05)".

8.3. Serializing relative color functions

The serialization of the result of a relative color function is a <color>, as defined in CSS Color 4 § 4.7 Serializing <color> Values. The form used is the same as that used to specify the relative color, but using the absolute form.

The minimum precision for round-tripping is the same as that specified in CSS Color 4 § 4.7.4 Serializing values of the color() function.

The result of serializing 
lch(from peru calc(l * 0.8) calc(c * 0.7) calc(h + 180))

is the string "lch(49.80224% 37.80819 243.6803)"

8.4. Serializing custom color-spaces

The precision with which color() component values are retained, and thus the number of significant figures in the serialized value, is not defined in this specification, but for CMYK color spaces must at least be sufficient to round-trip values with eight bit precision; this will result in at least two decimal places unless trailing zeroes have been omitted.

The serialized value of the color in

@color-profile --swop5c {src: url('https://example.org/SWOP2006_Coated5v2.icc');
}
.header {
background-color:    color(--swop5c  0% 70.0% 20.00% .0%);
}

is the string "color(--swop5c 0 0.7 0.2 0)"

8.5. Serializing device-cmyk values

The serialized form of device-cmyk() values is derived from the computed value and uses the device-cmyk() form, with lowercase letters for the function name.

The component values are serialized in base 10, as <number>. A single ASCII space character " " must be used as the separator between the component values.

Trailing fractional zeroes in any component values must be omitted; if the fractional part consists of all zeroes, the decimal point must also be omitted.

The serialized value of the color

  device-cmyk(0 81% 81% 30%)

is the string "device-cmyk(0 0.81 0.81 0.3)"

The precision with which device-cmyk() component values are retained, and thus the number of significant figures in the serialized value, is not defined in this specification, but must at least be sufficient to round-trip values with eight bit precision; this will result in at least two decimal places unless trailing zeroes have been omitted. Values must be rounded towards +∞, not truncated.

Unitary alpha values are not explicitly serialized. Non-unitary alpha values must be explicitly serialized, and the string " / " (an ASCII space, then forward slash, then another space) must be used to separate the black ("k") color component value from the alpha value.

9. Default Style Rules

The following stylesheet is informative, not normative. This style sheet could be used by an implementation as part of its default styling of HTML4, HTML5, XHTML1, XHTML1.1, XHTML Basic, and other XHTML Family documents.

/* traditional desktop user agent colors for hyperlinks */
:link { color: LinkText; }
:visited { color: VisitedText; }
:active { color: ActiveText; }

/* a reasonable, conservative default for device-cmyk */
@color-profile device-cmyk {
  src: url('https://drafts.csswg.org/css-color-4/ICCprofiles/Coated_Fogra39L_VIGC_300.icc');
}

10. Security Considerations

This specification adds to CSS the on-demand downloading of ICC profiles. These do not contain executable code, and thus do not constitute an increased security risk.

11. Privacy Considerations

No new privacy considerations have been reported on this specification.

12. Accessibility Considerations

This specification introduces a new feature to help stylesheet authors write stylesheets which conform to WCAG 2.1 section 1.4.3 Contrast (Minimum).

13. Changes

13.1. Since the Working Draft of 1 June 2021

13.2. Since the FPWD of 10 June 2020

13.3. Changes from Colors 4

One major change, compared to CSS Color 4, is that CSS colors are no longer restricted to predefined RGB spaces such as sRGB or display-p3.

To support this, several brand new features have been added:

  1. The color() function is extended by the @color-profile at-rule, for profiled device-dependent color, including calibrated CMYK.
  2. device-cmyk() function, for specifying uncalibrated colors in an output-device-specific CMYK color space.

In addition the new color-mix() function allows two colors to be mixed, in a specified colorspace, to yeild a new color.

The new color-contrast() function allows one of a list of colors to be chosen, based on the WCAG 2.1 contrast with a specified color.

Conformance

Document conventions

Conformance requirements are expressed with a combination of descriptive assertions and RFC 2119 terminology. The key words “MUST”, “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”, “RECOMMENDED”, “MAY”, and “OPTIONAL” in the normative parts of this document are to be interpreted as described in RFC 2119. However, for readability, these words do not appear in all uppercase letters in this specification.

All of the text of this specification is normative except sections explicitly marked as non-normative, examples, and notes. [RFC2119]

Examples in this specification are introduced with the words “for example” or are set apart from the normative text with class="example", like this:

This is an example of an informative example.

Informative notes begin with the word “Note” and are set apart from the normative text with class="note", like this:

Note, this is an informative note.

Advisements are normative sections styled to evoke special attention and are set apart from other normative text with <strong class="advisement">, like this: UAs MUST provide an accessible alternative.

Conformance classes

Conformance to this specification is defined for three conformance classes:

style sheet
A CSS style sheet.
renderer
A UA that interprets the semantics of a style sheet and renders documents that use them.
authoring tool
A UA that writes a style sheet.

A style sheet is conformant to this specification if all of its statements that use syntax defined in this module are valid according to the generic CSS grammar and the individual grammars of each feature defined in this module.

A renderer is conformant to this specification if, in addition to interpreting the style sheet as defined by the appropriate specifications, it supports all the features defined by this specification by parsing them correctly and rendering the document accordingly. However, the inability of a UA to correctly render a document due to limitations of the device does not make the UA non-conformant. (For example, a UA is not required to render color on a monochrome monitor.)

An authoring tool is conformant to this specification if it writes style sheets that are syntactically correct according to the generic CSS grammar and the individual grammars of each feature in this module, and meet all other conformance requirements of style sheets as described in this module.

Partial implementations

So that authors can exploit the forward-compatible parsing rules to assign fallback values, CSS renderers must treat as invalid (and ignore as appropriate) any at-rules, properties, property values, keywords, and other syntactic constructs for which they have no usable level of support. In particular, user agents must not selectively ignore unsupported component values and honor supported values in a single multi-value property declaration: if any value is considered invalid (as unsupported values must be), CSS requires that the entire declaration be ignored.

Implementations of Unstable and Proprietary Features

To avoid clashes with future stable CSS features, the CSSWG recommends following best practices for the implementation of unstable features and proprietary extensions to CSS.

Non-experimental implementations

Once a specification reaches the Candidate Recommendation stage, non-experimental implementations are possible, and implementors should release an unprefixed implementation of any CR-level feature they can demonstrate to be correctly implemented according to spec.

To establish and maintain the interoperability of CSS across implementations, the CSS Working Group requests that non-experimental CSS renderers submit an implementation report (and, if necessary, the testcases used for that implementation report) to the W3C before releasing an unprefixed implementation of any CSS features. Testcases submitted to W3C are subject to review and correction by the CSS Working Group.

Further information on submitting testcases and implementation reports can be found from on the CSS Working Group’s website at https://www.w3.org/Style/CSS/Test/. Questions should be directed to the public-css-testsuite@w3.org mailing list.

Index

Terms defined by this specification

Terms defined by reference

References

Normative References

[CSS-CASCADE-5]
Elika Etemad; Miriam Suzanne; Tab Atkins Jr.. CSS Cascading and Inheritance Level 5. 3 December 2021. WD. URL: https://www.w3.org/TR/css-cascade-5/
[CSS-COLOR-4]
Tab Atkins Jr.; Chris Lilley. CSS Color Module Level 4. 1 June 2021. WD. URL: https://www.w3.org/TR/css-color-4/
[CSS-SYNTAX-3]
Tab Atkins Jr.; Simon Sapin. CSS Syntax Module Level 3. 16 July 2019. CR. URL: https://www.w3.org/TR/css-syntax-3/
[CSS-VALUES-4]
Tab Atkins Jr.; Elika Etemad. CSS Values and Units Module Level 4. 16 October 2021. WD. URL: https://www.w3.org/TR/css-values-4/
[CSSOM-1]
Daniel Glazman; Emilio Cobos Álvarez. CSS Object Model (CSSOM). 26 August 2021. WD. URL: https://www.w3.org/TR/cssom-1/
[FETCH]
Anne van Kesteren. Fetch Standard. Living Standard. URL: https://fetch.spec.whatwg.org/
[ICC]
ICC.1:2010 (Profile version 4.3.0.0). December 2010. URL: http://www.color.org/specification/ICC1v43_2010-12.pdf
[RFC2119]
S. Bradner. Key words for use in RFCs to Indicate Requirement Levels. March 1997. Best Current Practice. URL: https://datatracker.ietf.org/doc/html/rfc2119
[WCAG21]
Andrew Kirkpatrick; et al. Web Content Accessibility Guidelines (WCAG) 2.1. 5 June 2018. REC. URL: https://www.w3.org/TR/WCAG21/

Property Index

No properties defined.

@color-profile Descriptors

Name Value Initial
components <ident># n/a
rendering-intent relative-colorimetric | absolute-colorimetric | perceptual | saturation relative-colorimetric
src <url> n/a