mq() is a Sass mixin that helps you compose media queries in an elegant way.

• compiles keywords and px/em values to em-based queries (a good thing)
• provides fallbacks for older browsers (see Mobile-first Responsive Web Design and IE8 on the Guardian's developer blog).

Here is a very basic example:

$mq-breakpoints: (
    mobile:  320px,
    tablet:  740px,
    desktop: 980px,
    wide:    1300px
);

@import 'mq';

.foo {
    @include mq($from: mobile, $until: tablet) {
        background: red;
    }
    @include mq($from: tablet) {
        background: green;
    }
}

Compiles to:

@media (min-width: 20em) and (max-width: 46.24em) {
  .foo {
    background: red;
  }
}
@media (min-width: 46.25em) {
  .foo {
    background: green;
  }
}

Sass MQ was crafted in-house at the Guardian. Today, many more companies and developers are using it in their projects: see who uses Sass MQ.

Immediately play with it on SassMeister: @import 'mq';.

OR:

1. Install:

   • with Bower: bower install sass-mq --save
   • with npm: npm install sass-mq --save supports eyeglass
   • with yarn: yarn add sass-mq supports eyeglass

   OR Download _mq.scss into your Sass project.

2. Import the partial in your Sass files and override default settings with your own preferences before the file is imported:

   // To enable support for browsers that do not support @media queries,
   // (IE <= 8, Firefox <= 3, Opera <= 9) set $mq-responsive to false
   // Create a separate stylesheet served exclusively to these browsers,
   // meaning @media queries will be rasterized, relying on the cascade itself
   $mq-responsive: true;
   
   // Name your breakpoints in a way that creates a ubiquitous language
   // across team members. It will improve communication between
   // stakeholders, designers, developers, and testers.
   $mq-breakpoints: (
       mobile:  320px,
       tablet:  740px,
       desktop: 980px,
       wide:    1300px,
   
       // Tweakpoints
       desktopAd: 810px,
       mobileLandscape: 480px
   );
   
   // Define the breakpoint from the $mq-breakpoints list that should
   // be used as the target width when outputting a static stylesheet
   // (when $mq-responsive is set to 'false').
   $mq-static-breakpoint: desktop;
   
   // If you want to display the currently active breakpoint in the top
   // right corner of your site during development, add the breakpoints
   // to this list, ordered by width. For example: (mobile, tablet, desktop).
   $mq-show-breakpoints: (mobile, mobileLandscape, tablet, desktop, wide);
   
   // If _mq.scss is in your project:
   @import 'path/to/mq';
   // With eyeglass:
   @import 'sass-mq';
   // With webpack (and boilerplates such as create-react-app)
   @import '~sass-mq';

3. Play around with mq() (see below)

mq() takes up to three optional parameters:

• $from: inclusive min-width boundary
• $until: exclusive max-width boundary
• $and: additional custom directives

Note that $until as a keyword is a hard limit i.e. it's breakpoint - 1.

.responsive {
    // Apply styling to mobile and upwards
    @include mq($from: mobile) {
        color: red;
    }
    // Apply styling up to devices smaller than tablets (exclude tablets)
    @include mq($until: tablet) {
        color: blue;
    }
    // Same thing, in landscape orientation
    @include mq($until: tablet, $and: '(orientation: landscape)') {
        color: hotpink;
    }
    // Apply styling to tablets up to desktop (exclude desktop)
    @include mq(tablet, desktop) {
        color: green;
    }
}

To enable support for browsers that do not support @media queries, (IE <= 8, Firefox <= 3, Opera <= 9) set $mq-responsive: false.

Tip: create a separate stylesheet served exclusively to these browsers, for example with conditional comments.

When @media queries are rasterized, browsers rely on the cascade itself. Learn more about this technique on Jake’s blog.

To avoid rasterizing styles intended for displays larger than what those older browsers typically run on, set $mq-static-breakpoint to match a breakpoint from the $mq-breakpoints list. The default is desktop.

The static output will only include @media queries that start at or span this breakpoint and which have no custom $and directives:

$mq-responsive:        false;
$mq-static-breakpoint: desktop;

.static {
    // Queries that span or start at desktop are compiled:
    @include mq($from: mobile) {
        color: lawngreen;
    }
    @include mq(tablet, wide) {
        color: seagreen;
    }
    @include mq($from: desktop) {
        color: forestgreen;
    }

    // But these queries won’t be compiled:
    @include mq($until: tablet) {
        color: indianred;
    }
    @include mq($until: tablet, $and: '(orientation: landscape)') {
        color: crimson;
    }
    @include mq(mobile, desktop) {
        color: firebrick;
    }
}

Sometimes you’ll want to be extra verbose (for example, if you’re developing a library based on top of sass-mq), however for readability in a codebase, the shorthand notation is recommended.

All of these examples output the exact same thing, and are here for reference so you can use the notation that best matches your needs:

// Verbose
@include mq(
    $from: false,
    $until: desktop,
    $and: false,
    $media-type: $mq-media-type // defaults to 'all'
) {
    .foo {}
}

// Omitting argument names
@include mq(
    false,
    desktop,
    false,
    $mq-media-type
) {
    .foo {}
}

// Omitting tailing arguments
@include mq(false, desktop) {
    .foo {}
}

// Recommended
@include mq($until: desktop) {
    .foo {}
}

See the detailed API documentation

@include mq-add-breakpoint(tvscreen, 1920px);

.hide-on-tv {
    @include mq(tvscreen) {
        display: none;
    }
}

While developing, it can be nice to always know which breakpoint is active. To achieve this, set the $mq-show-breakpoints variable to be a list of the breakpoints you want to debug, ordered by width. The name of the active breakpoint and its pixel and em values will then be shown in the top right corner of the viewport.

// Adapt the list to include breakpoint names from your project
$mq-show-breakpoints: (phone, phablet, tablet);

If you want to specify a media type, for example to output styles for screens only, set $mq-media-type:

$mq-media-type: screen;

.screen-only-element {
    @include mq(mobile) {
        width: 300px;
    }
}

@media screen and (max-width: 19.99em) {
    .screen-only-element {
        width: 300px;
    }
}

npm test

Sass MQ is documented using SassDoc.

Generate the documentation locally:

sassdoc .

Generate & deploy the documentation to http://sass-mq.github.io/sass-mq/:

npm run sassdoc

• https://github.com/alphagov/govuk_frontend_toolkit/blob/master/stylesheets/_conditionals.scss
• https://github.com/bits-sass/helpers-responsive/blob/master/_responsive.scss
• https://gist.github.com/magsout/5978325

• http://jakearchibald.github.io/sass-ie/
• http://nicolasgallagher.com/mobile-first-css-sass-and-ie/
• http://cognition.happycog.com/article/fall-back-to-the-cascade
• http://www.theguardian.com/info/developer-blog/2013/oct/14/mobile-first-responsive-ie8

Sass MQ was developed in-house at the Guardian.

These companies and projects use Sass MQ:

• The Guardian
• BBC (Homepage, Sport, News, Programmes)
• The Financial Times
• Rightmove
• Stockholm International Fairs and Congress Centre
• Beyond
• EQ Design
• Baseguide
• Base Creative
• Locomotive
• Le Figaro (TV Mag)
• LunaWeb
• inuitcss
• Hotelbeds Group
• Beneš & Michl
• Manchester International Festival
• Shopify Polaris
• Taylor / Thomas
• GOV.UK Design System
• You? Open an issue

Looking for a more advanced sass-mq, with support for height and other niceties?
Give @mcaskill's fork of sass-mq a try.