Built-In Modules

Dart Sass: since 1.23.0
LibSass: ✗
Ruby Sass: ✗

Only Dart Sass currently supports loading built-in modules with @use. Users of other implementations must call functions using their global names instead.

Sass provides many built-in modules which contain useful functions (and the occasional mixin). These modules can be loaded with the @use rule like any user-defined stylesheet, and their functions can be called like any other module member. All built-in module URLs begin with sass: to indicate that they're part of Sass itself.

⚠️ Heads up!

Before the Sass module system was introduced, all Sass functions were globally available at all times. Many functions still have global aliases (these are listed in their documentation). The Sass team discourages their use and will eventually deprecate them, but for now they remain available for compatibility with older Sass versions and with LibSass (which doesn’t support the module system yet).

A few functions are only available globally even in the new module system, either because they have special evaluation behavior (if()) or because they add extra behavior on top of built-in CSS functions (rgb() and hsl()). These will not be deprecated and can be used freely.

SCSS
Sass
CSS
SCSS Syntax@use "sass:color";

.button {
  $primary-color: #6b717f;
  color: $primary-color;
  border: 1px solid color.scale($primary-color, $lightness: 20%);
}
Sass Syntax@use "sass:color"

.button
  $primary-color: #6b717f
  color: $primary-color
  border: 1px solid color.scale($primary-color, $lightness: 20%)

CSS Output.button {
  color: #6b717f;
  border: 1px solid #878d9a;
}

Sass provides the following built-in modules:

The sass:math module provides functions that operate on numbers.
The sass:string module makes it easy to combine, search, or split apart strings.
The sass:color module generates new colors based on existing ones, making it easy to build color themes.
The sass:list module lets you access and modify values in lists.
The sass:map module makes it possible to look up the value associated with a key in a map, and much more.
The sass:selector module provides access to Sass’s powerful selector engine.
The sass:meta module exposes the details of Sass’s inner workings.

Global Functions permalinkGlobal Functions

hsl($hue $saturation $lightness)
hsl($hue $saturation $lightness / $alpha)
hsl($hue, $saturation, $lightness, $alpha: 1)
hsla($hue $saturation $lightness)
hsla($hue $saturation $lightness / $alpha)
hsla($hue, $saturation, $lightness, $alpha: 1) //=> color

Dart Sass: since 1.15.0
LibSass: ✗
Ruby Sass: ✗

LibSass and Ruby Sass only support the following signatures:

hsl($hue, $saturation, $lightness)
hsla($hue, $saturation, $lightness, $alpha)

Note that for these implementations, the $alpha argument is required if the function name hsla() is used, and forbidden if the function name hsl() is used.

Dart Sass: ✓
LibSass: ✗
Ruby Sass: since 3.7.0

LibSass and older versions of Ruby Sass don’t support alpha values specified as percentages.

Returns a color with the given hue, saturation, and lightness and the given alpha channel.

The hue is a number between 0deg and 360deg (inclusive) and may be unitless. The saturation and lightness are numbers between 0% and 100% (inclusive) and may not be unitless. The alpha channel can be specified as either a unitless number between 0 and 1 (inclusive), or a percentage between 0% and 100% (inclusive).

💡 Fun fact:

You can pass special functions like calc() or var() in place of any argument to hsl(). You can even use var() in place of multiple arguments, since it might be replaced by multiple values! When a color function is called this way, it returns an unquoted string using the same signature it was called with.

SCSS
Sass
SCSS Syntax@debug hsl(210deg 100% 20% / var(--opacity)); // hsl(210deg 100% 20% / var(--opacity))
@debug hsla(var(--peach), 20%); // hsla(var(--peach), 20%)
Sass Syntax@debug hsl(210deg 100% 20% / var(--opacity))  // hsl(210deg 100% 20% / var(--opacity))
@debug hsla(var(--peach), 20%)  // hsla(var(--peach), 20%)

⚠️ Heads up!

Sass’s special parsing rules for slash-separated values make it difficult to pass variables for $lightness or $alpha when using the hsl($hue $saturation $lightness / $alpha) signature. Consider using hsl($hue, $saturation, $lightness, $alpha) instead.

SCSS
Sass
SCSS Syntax@debug hsl(210deg 100% 20%); // #036
@debug hsl(34, 35%, 92%); // #f2ece4
@debug hsl(210deg 100% 20% / 50%); // rgba(0, 51, 102, 0.5)
@debug hsla(34, 35%, 92%, 0.2); // rgba(242, 236, 228, 0.2)
Sass Syntax@debug hsl(210deg 100% 20%) // #036
@debug hsl(34, 35%, 92%) // #f2ece4
@debug hsl(210deg 100% 20% / 50%)  // rgba(0, 51, 102, 0.5)
@debug hsla(34, 35%, 92%, 0.2)  // rgba(242, 236, 228, 0.2)

if($condition, $if-true, $if-false)

Returns $if-true if $condition is truthy, and $if-false otherwise.

This function is special in that it doesn’t even evaluate the argument that isn’t returned, so it’s safe to call even if the unused argument would throw an error.

SCSS
Sass
SCSS Syntax@debug if(true, 10px, 15px); // 10px
@debug if(false, 10px, 15px); // 15px
@debug if(variable-defined($var), $var, null); // null
Sass Syntax@debug if(true, 10px, 15px)  // 10px
@debug if(false, 10px, 15px)  // 15px
@debug if(variable-defined($var), $var, null)  // null

rgb($red $green $blue)
rgb($red $green $blue / $alpha)
rgb($red, $green, $blue, $alpha: 1)
rgb($color, $alpha)
rgba($red $green $blue)
rgba($red $green $blue / $alpha)
rgba($red, $green, $blue, $alpha: 1)
rgba($color, $alpha) //=> color

Dart Sass: since 1.15.0
LibSass: ✗
Ruby Sass: ✗

LibSass and Ruby Sass only support the following signatures:

rgb($red, $green, $blue)
rgba($red, $green, $blue, $alpha)
rgba($color, $alpha)

Note that for these implementations, the $alpha argument is required if the function name rgba() is used, and forbidden if the function name rgb() is used.

Dart Sass: ✓
LibSass: ✗
Ruby Sass: since 3.7.0

LibSass and older versions of Ruby Sass don’t support alpha values specified as percentages.

If $red, $green, $blue, and optionally $alpha are passed, returns a color with the given red, green, blue, and alpha channels.

Each channel can be specified as either a unitless number between 0 and 255 (inclusive), or a percentage between 0% and 100% (inclusive). The alpha channel can be specified as either a unitless number between 0 and 1 (inclusive), or a percentage between 0% and 100% (inclusive).

💡 Fun fact:

You can pass special functions like calc() or var() in place of any argument to rgb(). You can even use var() in place of multiple arguments, since it might be replaced by multiple values! When a color function is called this way, it returns an unquoted string using the same signature it was called with.

SCSS
Sass
SCSS Syntax@debug rgb(0 51 102 / var(--opacity)); // rgb(0 51 102 / var(--opacity))
@debug rgba(var(--peach), 0.2); // rgba(var(--peach), 0.2)
Sass Syntax@debug rgb(0 51 102 / var(--opacity))  // rgb(0 51 102 / var(--opacity))
@debug rgba(var(--peach), 0.2)  // rgba(var(--peach), 0.2)

⚠️ Heads up!

Sass’s special parsing rules for slash-separated values make it difficult to pass variables for $blue or $alpha when using the rgb($red $green $blue / $alpha) signature. Consider using rgb($red, $green, $blue, $alpha) instead.

SCSS
Sass
SCSS Syntax@debug rgb(0 51 102); // #036
@debug rgb(95%, 92.5%, 89.5%); // #f2ece4
@debug rgb(0 51 102 / 50%); // rgba(0, 51, 102, 0.5)
@debug rgba(95%, 92.5%, 89.5%, 0.2); // rgba(242, 236, 228, 0.2)
Sass Syntax@debug rgb(0 51 102)  // #036
@debug rgb(95%, 92.5%, 89.5%)  // #f2ece4
@debug rgb(0 51 102 / 50%)  // rgba(0, 51, 102, 0.5)
@debug rgba(95%, 92.5%, 89.5%, 0.2)  // rgba(242, 236, 228, 0.2)

If $color and $alpha are passed, this returns $color with the given $alpha channel instead of its original alpha channel.

SCSS
Sass
SCSS Syntax@debug rgb(#f2ece4, 50%); // rgba(242, 236, 228, 0.5);
@debug rgba(rgba(0, 51, 102, 0.5), 1); // #003366
Sass Syntax@debug rgb(#f2ece4, 50%)  // rgba(242, 236, 228, 0.5) 
@debug rgba(rgba(0, 51, 102, 0.5), 1)  // #003366