css/docs/content/support/breakpoints.md

title	path	status	source	bundle
Breakpoints	support/breakpoints	Stable	https://github.com/primer/css/blob/master/src/support/variables/layout.scss	support

Our breakpoints are based on screen widths where our content starts to break. Our breakpoints may change as we move more of the product into responsive layouts.

We use abbreviations for each breakpoint to keep the class names concise. This abbreviated syntax is used consistently across responsive styles. Responsive styles allow you to change the styles properties at each breakpoint. For example, when using column widths for grid layouts, you can specify that the width is 12 columns wide by default, 8 columns from the medium breakpoint, and 4 columns wide from the extra large breakpoint: <div class="col-12 col-md-8 col-xl-4">...</div>.

Breakpoint	Syntax	Breaks at
Small	sm	544px
Medium	md	768px
Large	lg	1012px
Extra-large	xl	1280px

Responsive styles are available for margin, padding, layout, flexbox, the grid system, and many more.

Breakpoint and up... 🛫

In most cases, breakpoints get used with the min-width media query. This means that when using a responsive utility class, the class becomes "enabled" from the breakpoint on upwards. Or from the browser's perspective, when the browser's width is the breakpoint or wider.

Breakpoint	Syntax	Is enabled...
None		from 0px upwards ->
Small	sm	from 544px upwards ->
Medium	md	from 768px upwards ->
Large	lg	from 1012px upwards ->
Extra-large	xl	from 1280px upwards ->

A responsive utility class stays enabled unless it gets overridden with another responsive utility class that has a higher breakpoint. Here the example from above <div class="col-12 col-md-8 col-xl-4">...</div> visualized:

| 0px -> 
         | 544px ->  
         | sm
                    | 768px ->  
                    | md 
                               | 1012px ->  
                               | lg
                                           | 1280px ->
                                           | xl

| col-12 ---------> | col-md-8 ----------> | col-xl-4 ->

Using breakpoints with the min-width media query works great for "mobile first". Design for mobile devices as a default, then if needed, tweak it for wider desktop screens using responsive utility classes.

Note: The responsive hide utilities are an exception and use a range between two breakpoints. They also go the other direction "breakpoint and down... 🛬". For example .hide-md hides an element if the browser's width is between sm <-> md (544px - 767px).

Breakpoint variables

The above values are defined as variables, and then put into a Sass map that generates the media query mixin.

// breakpoints
$width-xs: 0;
$width-sm: 544px;
$width-md: 768px;
$width-lg: 1012px;
$width-xl: 1280px;

$breakpoints: (
  // Small screen / phone
    sm: $width-sm,
  // Medium screen / tablet
    md: $width-md,
  // Large screen / desktop (980 + (12 * 2)) <= container + gutters
    lg: $width-lg,
  // Extra large screen / wide desktop
    xl: $width-xl
) !default;

Media query mixins

Use media query mixins when you want to change CSS properties at a particular breakpoint. The media query mixin works by passing in a breakpoint value, such as breakpoint(md).

Media queries are scoped from each breakpoint and upwards. In the example below, the font size is 28px until the viewport size meets the md breakpoint, from there upwards—including through the xl breakpoint—the font size will be 32px.

.styles {
  font-size: 28px;
  @include breakpoint(md) {
    font-size: 32px;
  }
}

Responsive variants

The $responsive-variants variable is a mapping of breakpoints to classname variants, and should be used like so:

@each $breakpoint, $variant in $responsive-variants {
  @include breakpoint($breakpoint) {
    // Note: the first iteration gets `$variant == ""`
    .overflow#{$variant}-auto {
      overflow: auto;
    }
  }
}

The resulting CSS would be:

.overflow-auto {
  overflow: auto;
}
@media (min-width: 544px) {
  .overflow-sm-auto {
    overflow: auto;
  }
}
@media (min-width: 768px) {
  .overflow-md-auto {
    overflow: auto;
  }
}
@media (min-width: 1012px) {
  .overflow-lg-auto {
    overflow: auto;
  }
}
@media (min-width: 1280px) {
  .overflow-xl-auto {
    overflow: auto;
  }
}

Caution!

1. Don't precede the #{$variation} interpolation with a hyphen because the first value of $variant will be an empty string.
2. For consistency, please put the @include breakpoint($breakpoint) call directly inside the $responsive-variants loop. This will help keep file sizes small by "batching" selectors in shared @media queries.