sass-site/source/documentation/at-rules/use.md

title	table_of_contents	eleventyComputed	introduction
@use	true	before_introduction {% render 'doc_snippets/module-system-status' %}	The `@use` rule loads [mixins](/documentation/at-rules/mixin), [functions](/documentation/at-rules/function), and [variables](/documentation/variables) from other Sass stylesheets, and combines CSS from multiple stylesheets together. Stylesheets loaded by `@use` are called "modules". Sass also provides [built-in modules](/documentation/modules) full of useful functions.

The simplest @use rule is written @use "<url>", which loads the module at the given URL. Any styles loaded this way will be included exactly once in the compiled CSS output, no matter how many times those styles are loaded.

{% headsUp %} A stylesheet's @use rules must come before any rules other than @forward, including style rules. However, you can declare variables before @use rules to use when configuring modules.

{% endheadsUp %}

{% codeExample 'use' %} // foundation/_code.scss code { padding: .25em; line-height: 0; }

// foundation/_lists.scss ul, ol { text-align: left;

& & {
  padding: {
    bottom: 0;
    left: 0;
  }
}

}

// style.scss @use 'foundation/code'; @use 'foundation/lists';

// foundation/_code.sass code padding: .25em line-height: 0

// foundation/_lists.sass ul, ol text-align: left

& &
  padding:
    bottom: 0
    left: 0

---

// style.sass @use 'foundation/code' @use 'foundation/lists'

code { padding: .25em; line-height: 0; }

ul, ol { text-align: left; } ul ul, ol ol { padding-bottom: 0; padding-left: 0; } {% endcodeExample %}

Loading Members

You can access variables, functions, and mixins from another module by writing <namespace>.<variable>, <namespace>.<function>(), or @include <namespace>.<mixin>(). By default, the namespace is just the last component of the module's URL.

Members (variables, functions, and mixins) loaded with @use are only visible in the stylesheet that loads them. Other stylesheets will need to write their own @use rules if they also want to access them. This helps make it easy to figure out exactly where each member is coming from. If you want to load members from many files at once, you can use the @forward rule to forward them all from one shared file.

{% funFact %} Because @use adds namespaces to member names, it's safe to choose very simple names like $radius or $width when writing a stylesheet. This is different from the old @import rule, which encouraged that users write long names like $mat-corner-radius to avoid conflicts with other libraries, and it helps keep your stylesheets clear and easy to read!

{% endfunFact %}

{% codeExample 'loading-members' %} // src/_corners.scss $radius: 3px;

@mixin rounded { border-radius: $radius; }

// style.scss @use "src/corners";

.button { @include corners.rounded; padding: 5px + corners.$radius; }

// src/_corners.sass $radius: 3px

@mixin rounded border-radius: $radius

// style.sass @use "src/corners"

.button @include corners.rounded padding: 5px + corners.$radius

.button { border-radius: 3px; padding: 8px; } {% endcodeExample %}

Choosing a Namespace

By default, a module's namespace is just the last component of its URL without a file extension. However, sometimes you might want to choose a different namespace—you might want to use a shorter name for a module you refer to a lot, or you might be loading multiple modules with the same filename. You can do this by writing @use "<url>" as <namespace>.

{% codeExample 'namespace' %} // src/_corners.scss $radius: 3px;

@mixin rounded { border-radius: $radius; }

// style.scss @use "src/corners" as c;

.button { @include c.rounded; padding: 5px + c.$radius; }

// src/_corners.sass $radius: 3px

@mixin rounded border-radius: $radius

// style.sass @use "src/corners" as c

.button @include c.rounded padding: 5px + c.$radius

.button { border-radius: 3px; padding: 8px; } {% endcodeExample %}

You can even load a module without a namespace by writing @use "<url>" as *. We recommend you only do this for stylesheets written by you, though; otherwise, they may introduce new members that cause name conflicts!

{% codeExample 'use-url' %} // src/_corners.scss $radius: 3px;

@mixin rounded { border-radius: $radius; }

// style.scss @use "src/corners" as *;

.button { @include rounded; padding: 5px + $radius; }

// src/_corners.sass $radius: 3px

@mixin rounded border-radius: $radius

// style.sass @use "src/corners" as *

.button @include rounded padding: 5px + $radius

.button { border-radius: 3px; padding: 8px; } {% endcodeExample %}

Private Members

As a stylesheet author, you may not want all the members you define to be available outside your stylesheet. Sass makes it easy to define a private member by starting its name with either - or _. These members will work just like normal within the stylesheet that defines them, but they won't be part of a module's public API. That means stylesheets that load your module can't see them!

{% funFact %} If you want to make a member private to an entire package rather than just a single module, just don't forward its module from any of your package's entrypoints (the stylesheets you tell your users to load to use your package). You can even hide that member while forwarding the rest of its module!

{% endfunFact %}

{% codeExample 'private-members', false %} // src/_corners.scss $-radius: 3px;

@mixin rounded { border-radius: $-radius; }

// style.scss @use "src/corners";

.button { @include corners.rounded;

// This is an error! $-radius isn't visible outside of `_corners.scss`.
padding: 5px + corners.$-radius;

}

// src/_corners.sass $-radius: 3px

@mixin rounded border-radius: $-radius

// style.sass @use "src/corners"

.button @include corners.rounded

// This is an error! $-radius isn't visible outside of `_corners.scss`.
padding: 5px + corners.$-radius

{% endcodeExample %}

Configuration

A stylesheet can define variables with the !default flag to make them configurable. To load a module with configuration, write @use <url> with (<variable>: <value>, <variable>: <value>). The configured values will override the variables' default values.

{% render 'code_snippets/example-use-with' %}

With Mixins

Configuring modules with @use ... with can be very handy, especially when using libraries that were originally written to work with the @import rule. But it's not particularly flexible, and we don't recommend it for more advanced use-cases. If you find yourself wanting to configure many variables at once, pass maps as configuration, or update the configuration after the module is loaded, consider writing a mixin to set your variables instead and another mixin to inject your styles.

{% codeExample 'with-mixins' %} // _library.scss $-black: #000; $-border-radius: 0.25rem; $-box-shadow: null;

/// If the user has configured $-box-shadow, returns their configured value. /// Otherwise returns a value derived from $-black. @function -box-shadow() { @return $-box-shadow or (0 0.5rem 1rem rgba($-black, 0.15)); }

@mixin configure($black: null, $border-radius: null, $box-shadow: null) { @if $black { $-black: $black !global; } @if $border-radius { $-border-radius: $border-radius !global; } @if $box-shadow { $-box-shadow: $box-shadow !global; } }

@mixin styles { code { border-radius: $-border-radius; box-shadow: -box-shadow(); } }

// style.scss @use 'library';

@include library.configure( $black: #222, $border-radius: 0.1rem );

@include library.styles;

// _library.sass $-black: #000 $-border-radius: 0.25rem $-box-shadow: null

/// If the user has configured $-box-shadow, returns their configured value. /// Otherwise returns a value derived from $-black. @function -box-shadow() @return $-box-shadow or (0 0.5rem 1rem rgba($-black, 0.15))

@mixin configure($black: null, $border-radius: null, $box-shadow: null) @if $black $-black: $black !global @if $border-radius $-border-radius: $border-radius !global @if $box-shadow $-box-shadow: $box-shadow !global

@mixin styles code border-radius: $-border-radius box-shadow: -box-shadow()

// style.sass @use 'library' @include library.configure($black: #222, $border-radius: 0.1rem) @include library.styles

code { border-radius: 0.1rem; box-shadow: 0 0.5rem 1rem rgba(34, 34, 34, 0.15); } {% endcodeExample %}

Reassigning Variables

After loading a module, you can reassign its variables.

{% codeExample 'reassigning-variables', false %} // _library.scss $color: red;

// _override.scss @use 'library'; library.$color: blue;

// style.scss @use 'library'; @use 'override'; @debug library.$color; //=> blue

// _library.sass $color: red

// _override.sass @use 'library' library.$color: blue

// style.sass @use 'library' @use 'override' @debug library.$color //=> blue {% endcodeExample %}

This even works if you import a module without a namespace using as *. Assigning to a variable name defined in that module will overwrite its value in that module.

{% headsUp %} Built-in module variables (such as math.$pi) cannot be reassigned.

{% endheadsUp %}

Finding the Module

It wouldn't be any fun to write out absolute URLs for every stylesheet you load, so Sass's algorithm for finding a module makes it a little easier. For starters, you don't have to explicitly write out the extension of the file you want to load; @use "variables" will automatically load variables.scss, variables.sass, or variables.css.

{% headsUp %} To ensure that stylesheets work on every operating system, Sass loads files by URL, not by file path. This means you need to use forward slashes, not backslashes, even on Windows. {% endheadsUp %}

Load Paths

All Sass implementations allow users to provide load paths: paths on the filesystem that Sass will look in when locating modules. For example, if you pass node_modules/susy/sass as a load path, you can use @use "susy" to load node_modules/susy/sass/susy.scss.

Modules will always be loaded relative to the current file first, though. Load paths will only be used if no relative file exists that matches the module's URL. This ensures that you can't accidentally mess up your relative imports when you add a new library.

{% funFact %} Unlike some other languages, Sass doesn't require that you use ./ for relative imports. Relative imports are always available. {% endfunFact %}

Partials

As a convention, Sass files that are only meant to be loaded as modules, not compiled on their own, begin with _ (as in _code.scss). These are called partials, and they tell Sass tools not to try to compile those files on their own. You can leave off the _ when importing a partial.

Index Files

If you write an _index.scss or _index.sass in a folder, the index file will be loaded automatically when you load the URL for the folder itself.

{% codeExample 'index-files' %} // foundation/_code.scss code { padding: .25em; line-height: 0; }

// foundation/_lists.scss ul, ol { text-align: left;

& & {
  padding: {
    bottom: 0;
    left: 0;
  }
}

}

// foundation/_index.scss @use 'code'; @use 'lists';

// style.scss @use 'foundation';

// foundation/_code.sass code padding: .25em line-height: 0

// foundation/_lists.sass ul, ol text-align: left

& &
  padding:
    bottom: 0
    left: 0

---

// foundation/_index.sass @use 'code' @use 'lists'

// style.sass @use 'foundation'

code { padding: .25em; line-height: 0; }

ul, ol { text-align: left; } ul ul, ol ol { padding-bottom: 0; padding-left: 0; } {% endcodeExample %}

Loading CSS

In addition to loading .sass and .scss files, Sass can load plain old .css files.

{% codeExample 'loading-css' %} // code.css code { padding: .25em; line-height: 0; }

// style.scss @use 'code';

// code.css code { padding: .25em; line-height: 0; }

// style.sass @use 'code'

code { padding: .25em; line-height: 0; } {% endcodeExample %}

CSS files loaded as modules don't allow any special Sass features and so can't expose any Sass variables, functions, or mixins. In order to make sure authors don't accidentally write Sass in their CSS, all Sass features that aren't also valid CSS will produce errors. Otherwise, the CSS will be rendered as-is. It can even be extended!

Differences From @import

The @use rule is intended to replace the old @import rule, but it's intentionally designed to work differently. Here are some major differences between the two:

• @use only makes variables, functions, and mixins available within the scope of the current file. It never adds them to the global scope. This makes it easy to figure out where each name your Sass file references comes from, and means you can use shorter names without any risk of collision.

• @use only ever loads each file once. This ensures you don't end up accidentally duplicating your dependencies' CSS many times over.

• @use must appear at the beginning your file, and cannot be nested in style rules.

• Each @use rule can only have one URL.

• @use requires quotes around its URL, even when using the indented syntax.