@import

Sass extends CSS’s @import rule with the ability to import Sass and CSS stylesheets, providing access to mixins, functions, and variables and combining multiple stylesheets’ CSS together. Unlike plain CSS imports, which require the browser to make multiple HTTP requests as it renders your page, Sass imports are handled entirely during compilation.

Sass imports have the same syntax as CSS imports, except that they allow multiple imports to be separated by commas rather than requiring each one to have its own @import. Also, in the indented syntax, imported URLs aren’t required to have quotes.

⚠️ Heads up!

As of Dart Sass 1.80.0, the @import rule is deprecated and will be removed from the language in Dart Sass 3.0.0. Prefer the @use rule instead.

What’s Wrong With @import?

The @import rule has a number of serious issues:

  • @import makes all variables, mixins, and functions globally accessible. This makes it very difficult for people (or tools) to tell where anything is defined.

  • Because everything’s global, libraries must add a prefix to all their members to avoid naming collisions.

  • @extend rules are also global, which makes it difficult to predict which style rules will be extended.

  • Each stylesheet is executed and its CSS emitted every time it’s @imported, which increases compilation time and produces bloated output.

  • There was no way to define private members or placeholder selectors that were inaccessible to downstream stylesheets.

The new module system and the @use rule address all these problems.

How Do I Migrate?

We’ve written a migration tool that automatically converts most @import-based code to @use-based code in a flash. Just point it at your entrypoints and let it run!

SCSS Syntax

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

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

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

// style.scss
@import 'foundation/code', 'foundation/lists';

When Sass imports a file, that file is evaluated as though its contents appeared directly in place of the @import. Any mixins, functions, and variables from the imported file are made available, and all its CSS is included at the exact point where the @import was written. What’s more, any mixins, functions, or variables that were defined before the @import (including from other @imports) are available in the imported stylesheet.

⚠️ Heads up!

If the same stylesheet is imported more than once, it will be evaluated again each time. If it just defines functions and mixins, this usually isn’t a big deal, but if it contains style rules they’ll be compiled to CSS more than once.

Finding the FileFinding the File permalink

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

⚠️ Heads up!

To ensure that stylesheets work on every operating system, Sass imports files by URL, not by file path. This means you need to use forward slashes, not backslashes, even when you’re on Windows.

Load PathsLoad Paths permalink

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

Imports will always be resolved relative to the current file first, though. Load paths will only be used if no relative file exists that matches the import. This ensures that you can’t accidentally mess up your relative imports when you add a new library.

💡 Fun fact:

Unlike some other languages, Sass doesn’t require that you use ./ for relative imports. Relative imports are always available.

PartialsPartials permalink

As a convention, Sass files that are only meant to be imported, 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 FilesIndex Files permalink

Compatibility:
Dart Sass
✓
LibSass
since 3.6.0
Ruby Sass
since 3.6.0

If you write an _index.scss or _index.sass in a folder, when the folder itself is imported that file will be loaded in its place.

SCSS Syntax

// 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
@import 'code', 'lists';

// style.scss
@import 'foundation';

Custom ImportersCustom Importers permalink

All Sass implementations provide a way to define custom importers, which control how @imports locate stylesheets:

NestingNesting permalink

Imports are usually written at the top level of a stylesheet, but they don’t have to be. They can nested within style rules or plain CSS at-rules as well. The imported CSS is nested in that context, which makes nested imports useful for scoping a chunk of CSS to a particular element or media query. Top-level mixins, functions, and variables defined in the nested import are only available in the nested context.

SCSS Syntax

// _theme.scss
pre, code {
  font-family: 'Source Code Pro', Helvetica, Arial;
  border-radius: 4px;
}

// style.scss
.theme-sample {
  @import "theme";
}

💡 Fun fact:

Nested imports are very useful for scoping third-party stylesheets, but if you’re the author of the stylesheet you’re importing, it’s usually a better idea to write your styles in a mixin and include that mixin in the nested context. A mixin can be used in more flexible ways, and it’s clearer when looking at the imported stylesheet how it’s intended to be used.

⚠️ Heads up!

The CSS in nested imports is evaluated like a mixin, which means that any parent selectors will refer to the selector in which the stylesheet is nested.

SCSS Syntax

// _theme.scss
ul li {
  $padding: 16px;
  padding-left: $padding;
  [dir=rtl] & {
    padding: {
      left: 0;
      right: $padding;
    }
  }
}

// style.scss
.theme-sample {
  @import "theme";
}

Importing CSSImporting CSS permalink

Compatibility:
Dart Sass
since 1.11.0
LibSass
partial
Ruby Sass
✗

In addition to importing .sass and .scss files, Sass can import plain old .css files. The only rule is that the import must not explicitly include the .css extension, because that’s used to indicate a plain CSS @import.

SCSS Syntax

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

// style.scss
@import 'code';

CSS files imported by Sass don’t allow any special Sass features. 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!

Plain CSS @importsPlain CSS @imports permalink

Compatibility:
Dart Sass
✓
LibSass
partial
Ruby Sass
✓

Because @import is also defined in CSS, Sass needs a way of compiling plain CSS @imports without trying to import the files at compile time. To accomplish this, and to ensure SCSS is as much of a superset of CSS as possible, Sass will compile any @imports with the following characteristics to plain CSS imports:

  • Imports where the URL ends with .css.
  • Imports where the URL begins http:// or https://.
  • Imports where the URL is written as a url().
  • Imports that have media queries.
Playground

SCSS Syntax

@import "theme.css";
@import "http://fonts.googleapis.com/css?family=Droid+Sans";
@import url(theme);
@import "landscape" screen and (orientation: landscape);

InterpolationInterpolation permalink

Although Sass imports can’t use interpolation (to make sure it’s always possible to tell where mixins, functions, and variables come from), plain CSS imports can. This makes it possible to dynamically generate imports, for example based on mixin parameters.

Playground

SCSS Syntax

@mixin google-font($family) {
  @import url("http://fonts.googleapis.com/css?family=#{$family}");
}

@include google-font("Droid Sans");

Import and ModulesImport and Modules permalink

Compatibility:
Dart Sass
since 1.23.0
LibSass
✗
Ruby Sass
✗

Sass’s module system integrates seamlessly with @import, whether you’re importing a file that contains @use rules or loading a file that contains imports as a module. We want to make the transition from @import to @use as smooth as possible.

Importing a Module-System FileImporting a Module-System File permalink

When you import a file that contains @use rules, the importing file has access to all members (even private members) defined directly in that file, but not any members from modules that file has loaded. However, if that file contains @forward rules, the importing file will have access to forwarded members. This means that you can import a library that was written to be used with the module system.

⚠️ Heads up!

When a file with @use rules is imported, all the CSS transitively loaded by those is included in the resulting stylesheet, even if it’s already been included by another import. If you’re not careful, this can result in bloated CSS output!

Import-Only FilesImport-Only Files permalink

An API that makes sense for @use might not make sense for @import. For example, @use adds a namespace to all members by default so you can safely use short names, but @import doesn’t so you might need something longer. If you’re a library author, you may be concerned that if you update your library to use the new module system, your existing @import-based users will break.

To make this easier, Sass also supports import-only files. If you name a file <name>.import.scss, it will only be loaded for imports, not for @uses. This way, you can retain compatibility for @import users while still providing a nice API for users of the new module system.

SCSS Syntax

// _reset.scss

// Module system users write `@include reset.list()`.
@mixin list() {
  ul {
    margin: 0;
    padding: 0;
    list-style: none;
  }
}

// _reset.import.scss

// Legacy import users can keep writing `@include reset-list()`.
@forward "reset" as reset-*;

Configuring Modules Through ImportsConfiguring Modules Through Imports permalink

Compatibility:
Dart Sass
since 1.24.0
LibSass
✗
Ruby Sass
✗

You can configure modules that are loaded through an @import by defining global variables prior the @import that first loads that module.

SCSS Syntax

// _library.scss
$color: blue !default;

a {
  color: $color;
}

// _library.import.scss
@forward 'library' as lib-*;

// style.sass
$lib-color: green;
@import "library";

⚠️ Heads up!

Modules are only loaded once, so if you change the configuration after you @import a module for the first time (even indirectly), the change will be ignored if you @import the module again.

Loading a Module That Contains ImportsLoading a Module That Contains Imports permalink

When you use @use (or @forward) load a module that uses @import, that module will contain all the public members defined by the stylesheet you load and everything that stylesheet transitively imports. In other words, everything that’s imported is treated as though it were written in one big stylesheet.

This makes it easy to convert start using @use in a stylesheet even before all the libraries you depend on have converted to the new module system. Be aware, though, that if they do convert their APIs may well change!