High definition CSS color guide

CSS Color 4 brings wide gamut color tools and capabilities to the web: more colors, manipulation functions, and better gradients.

Adam Argyle
Adam Argyle

For over 25 years, sRGB (standard red green blue) has been the only color gamut for CSS gradients and colors, with color space offerings within it like rgb(), hsl() and hex. It is the most common color gamut capability amongst displays; a common denominator. We've grown accustomed to specifying colors within it.

The most popular color formats by percent of occurrences.

As displays become more capable of showing a wide range of colors, CSS needs a way to specify colors from within these wider ranges. The current color formats have no language for wide color ranges.

If CSS never updated, it would be stuck in the 90s color ranges forever, forced never to match the wide gamut offerings found in images and video. Trapped, only showing 30% of the colors the human eye can see. Thank CSS Color Level 4 for helping us escape, written primarily by Lea Verou and Chris Liley.

Chrome supports CSS Color 4 gamuts and color spaces. CSS can now support HD (high definition) displays, specifying colors from HD gamuts while also offering color spaces with specializations.

A series of images are shown transitioning between wide and narrow color gamuts, illustrating color vividness and its effects.
Try it for yourself

This guide has three parts. Read on to remember where color has been. Then, read where color is going and how to manage color in future by migrating to HD color.


In supported browsers, there's 50% more colors to pick from. If you thought 16 million colors sounded like a lot, wait until you see how many colors some of these new spaces can show. Also, think about all those gradients that banded because there wasn't enough bit-depth, that's resolved too.

In addition to more colors, arguably the most vivid colors the display is capable of, new color spaces provide unique tools and methods for managing and creating color systems. For example, before now we had HSL and its "lightness" channel, which was the best web developers had. Now in CSS, we have LCH's "perceptual lightness."

Two tables of color are side by side. The first table shows an HSL
    rainbow of 10 colors or so and next to it are grayscale colors that represent
    the lightness of those HSL colors. The second table shows an LCH rainbow,
    much less vibrant, but the grayscale colors next to it are consistent.
    This is showing how LCH has a healthy constant lightness value while HSL does not.
Preview for yourself on Codepen

Furthermore, gradients and mixing get some upgrades: color space support, hue interpolation options, and less banding.

The following image shows some of the mixing upgrades.

The top two color mixes are in sRGB with sRGB colors. The bottom two color mixes are in display p3. Display p3 has more vivid colors and the mixes result in black and white in the middle, where sRGB looks a bit desaturated and the mixes in the middle aren't black and white results.

The problem with color and the web is that CSS is not high definition ready, while the displays most folks have in their pockets, laps or mounted on walls are wide gamut, high definition color ready. The color capability of displays grew faster than CSS, now CSS is here to catch up.

There's much more than just "more colors." By the end of these documents, you'll be able to specify more colors, enhance gradients, and pick the best color spaces and color gamuts for each task.

What is a color gamut?

A gamut represents the size of something. The phrase "millions of colors" is a comment about the gamut of a display, or the range of colors it has to choose from. In the following image, three gamuts are compared, and the larger the size the more colors it offers.

Color gamuts are compared side by side as a triangle shape.
  sRGB is the smallest and Rec2020 is the largest.

A color gamut can also have a name. Like a basketball versus a baseball or a vente coffee cup versus a grande; a name for the size can help people communicate. Learning these color gamut names helps you communicate and quickly understand a range of colors.

This article reviews the previous color gamuts. You can read about the seven new gamuts in Access more colors and new spaces.

Human visual gamut

Color gamuts are often compared against the human visual gamut ; the entirety of color we believe the human eye can see. HVS is often portrayed with a chromaticity diagram, like this:

A horse shoe shape is filled with a vibrant gradient with a hollow triangle in the middle.
Source: Wikipedia

The outermost shape is what we can see as humans, and the inner triangle is the rgb() functions range, aka the sRGB color space.

As you saw triangles above, comparing gamut sizes, so will you find triangles below. This is the industry's way of communicating about color gamuts and comparing them.

What is a color space?

Color spaces are arrangements of a gamut, establishing a shape and a method of accessing colors. Many are simple 3D shapes like cubes or cylinders. This color arrangement determines which colors are next to each other, and how accessing and interpolating colors will work.

RGB is like a rectangular color space, where colors are accessed by specifying coordinates on 3 axes. HSL is a cylindrical color space, where colors are accessed with a hue angle and coordinates on 2 axes

A half cut open RGB cube and slices into HSL cylinder are shown side by side, to show how the colors are packed into a shape in each space.

The level 4 specification introduces 12 new color spaces for looking up colors. These are in addition to the 4 color spaces previously available:

Color gamut and color space summary

A color space is a mapping of colors where a color gamut is a range of colors. Consider a color gamut as a total of particles and a color space as a bottle made to hold that range of particles.

Here's an interactive visual by Alexey Ardov that demonstrates color spaces. Point, drag, and zoom around in this demo. Change the color space to see a visualization of other spaces.

  • Use color gamuts to talk about a range of colors, like low range or narrow gamut versus high range or wide gamut.
  • Use color spaces to talk about arrangements of color, syntax used to specify a color, manipulate color and interpolate through color.
A cube filled with many multiple colored dots.
Above is the sRGB gamut of particles fit into an RGB cube color space Image source

A review of the classic color spaces {#classic-color-spaces}

CSS Color 4 outlines a bunch of new features and tools for CSS and color. First, a recap of where color was before these new features.

Since the 2000s, you have been able to use the following for any CSS properties that accept a color as a value: hexadecimal (hex numbers), rgb(), rgba(), by name like hotpink, or with keywords like currentColor.

Around 2010, depending on your browser, CSS could use hsl() colors. Then in 2017, hex with alpha appeared. Last, only recently, hwb() started getting support in browsers.

All of these classic color spaces reference color within the same gamut, sRGB.


Browser Support

  • 1
  • 12
  • 1
  • 1


The hex colorspace specifies R, G, B and A with hexadecimal numbers. The following code examples show all the ways this syntax can specify red, green and blue plus opacity.

.valid-css-hex-colors {
  /* classic */
  --3-digits: #49b;
  --6-digits: #4499bb;

  /* hex with opacity */
  --4-digits-opaque: #f9bf;
  --8-digits-opaque: #ff99bbff;
  --4-digits-with-opacity: #49b8;
  --8-digits-with-opacity: #4499bb88;


Browser Support

  • 1
  • 12
  • 1
  • 1


The RGB color space features direct access to the red, green and blue channels. It allows specifying an amount between 0 and 255 or as a percentage 0 to 100. This syntax was around before some syntax normalization was in the specifications, so you'll see comma and no-comma syntaxes in the wild. Moving forward, commas are no longer required.

.valid-css-rgb-colors {
  --classic: rgb(64, 149, 191);
  --modern: rgb(64 149 191);
  --percents: rgb(25% 58% 75%);

  --classic-with-opacity-percent: rgba(64, 149, 191, 50%);
  --classic-with-opacity-decimal: rgba(64, 149, 191, .5);

  --modern-with-opacity-percent: rgb(64 149 191 / 50%);
  --modern-with-opacity-decimal: rgb(64 149 191 / .5);

  --percents-with-opacity-percent: rgb(25% 58% 75% / 50%);
  --percents-with-opacity-decimal: rgb(25% 58% 75% / 50%);

  --empty-channels: rgb(none none none);


Browser Support

  • 1
  • 12
  • 1
  • 3.1


One of the first color spaces to orient itself towards human language and communication, HSL (hue saturation and lightness) offers all the colors in the sRGB gamut while not requiring your brain to know how red, green and blue interact. Like RGB, it also originally had commas in the syntax, but moving forward, commas are no longer required.

.valid-css-hsl-colors {
  --classic: hsl(200deg, 50%, 50%);
  --modern: hsl(200 50% 50%);

  --classic-with-opacity-percent: hsla(200deg, 50%, 50%, 50%);
  --classic-with-opacity-decimal: hsla(200deg, 50%, 50%, .5);

  --modern-with-opacity-percent: hsl(200 50% 50% / 50%);
  --modern-with-opacity-decimal: hsl(200 50% 50% / .5);

  /* hueless and no saturation */
  --empty-channels-white: hsl(none none 100%);
  --empty-channels-black: hsl(none none 0%);


Browser Support

  • 101
  • 101
  • 96
  • 15


Another sRGB gamut color space oriented at how humans describe color is HWB (hue, whiteness, blackness). Authors can choose a hue and mix in white or black to find their desired color.

.valid-css-hwb-colors {
  --modern: hwb(200deg 25% 25%);
  --modern2: hwb(200 25% 25%);

  --modern-with-opacity-percent: hwb(200 25% 25% / 50%);
  --modern-with-opacity-decimal: hwb(200 25% 25% / .5);

  /* hueless and no saturation */
  --empty-channels-white: hwb(none 100% none);
  --empty-channels-black: hwb(none none 100%);

Next steps

Read about the new color spaces, syntaxes and tools, then learn how to migrate to HD color.

Non-sRGB color spaces on the web are in their early days, but we'll see an increase in usage from designers and developers over time. Knowing which color space to build a design system on, for example, is a strong tool to be in a creators toolbelt. Each color space offers unique features and a reason it was added to the CSS specification, and it's ok to start small with these and add as needed.


Read more of our color level 5 articles.

And, you can find additional reading across the web:

And tools: