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Background

Convey meaning through background-color and add decoration with gradients.

Background color

Similar to the contextual text color classes, set the background of an element to any contextual class. Background utilities do not set color, so in some cases you’ll want to use .text-* color utilities.

.bg-primary
.bg-secondary
.bg-success
.bg-danger
.bg-warning
.bg-info
.bg-light
.bg-dark
.bg-body
.bg-white
.bg-transparent
<div class="p-3 mb-2 bg-primary text-white">.bg-primary</div>
<div class="p-3 mb-2 bg-secondary text-white">.bg-secondary</div>
<div class="p-3 mb-2 bg-success text-white">.bg-success</div>
<div class="p-3 mb-2 bg-danger text-white">.bg-danger</div>
<div class="p-3 mb-2 bg-warning text-dark">.bg-warning</div>
<div class="p-3 mb-2 bg-info text-dark">.bg-info</div>
<div class="p-3 mb-2 bg-light text-dark">.bg-light</div>
<div class="p-3 mb-2 bg-dark text-white">.bg-dark</div>
<div class="p-3 mb-2 bg-body text-dark">.bg-body</div>
<div class="p-3 mb-2 bg-white text-dark">.bg-white</div>
<div class="p-3 mb-2 bg-transparent text-dark">.bg-transparent</div>

Background gradient

By adding a .bg-gradient class, a linear gradient is added as background image to the backgrounds. This gradient starts with a semi-transparent white which fades out to the bottom.

Do you need a gradient in your custom CSS? Just add background-image: var(gradient);.

.bg-primary.bg-gradient
.bg-secondary.bg-gradient
.bg-success.bg-gradient
.bg-danger.bg-gradient
.bg-warning.bg-gradient
.bg-info.bg-gradient
.bg-light.bg-gradient
.bg-dark.bg-gradient

Sass

In addition to the following Sass functionality, consider reading about our included CSS custom properties (aka CSS variables) for colors and more.

Variables

Most background-color utilities are generated by our theme colors, reassigned from our generic color palette variables.

$blue:    #0d6efd;
$indigo:  #6610f2;
$purple:  #6f42c1;
$pink:    #d63384;
$red:     #dc3545;
$orange:  #fd7e14;
$yellow:  #ffc107;
$green:   #198754;
$teal:    #20c997;
$cyan:    #0dcaf0;
$primary:       $primary-base;
$secondary:     $secondary-base;
$success:       $success-base;
$info:          $info-base;
$warning:       $warning-base;
$danger:        $danger-base;
$light:         $light-base;
$dark:          $dark-base;
$gradient: linear-gradient(180deg, rgba($white, .15), rgba($white, 0));

Grayscale colors are also available, but only a subset are used to generate any utilities.

$white:     #fff;
$gray-base: #3c4b64;
$gray-100:  #ebedef;
$gray-200:  #d8dbe0;
$gray-300:  #c4c9d0;
$gray-400:  #b1b7c1;
$gray-500:  #9da5b1;
$gray-600:  #8a93a2;
$gray-700:  #768192;
$gray-800:  #636f83;
$gray-900:  #4f5d73;
$black:     #000015;

Map

Theme colors are then put into a Sass map so we can loop over them to generate our utilities, component modifiers, and more.

$theme-colors: (
  "primary":    $primary,
  "secondary":  $secondary,
  "success":    $success,
  "info":       $info,
  "warning":    $warning,
  "danger":     $danger,
  "light":      $light,
  "dark":       $dark
);

Grayscale colors are also available as a Sass map. This map is not used to generate any utilities.

$grays: (
  "100": $gray-100,
  "200": $gray-200,
  "300": $gray-300,
  "400": $gray-400,
  "500": $gray-500,
  "600": $gray-600,
  "700": $gray-700,
  "800": $gray-800,
  "900": $gray-900
);

Mixins

No mixins are used to generate our background utilities, but we do have some additional mixins for other situations where you’d like to create your own gradients.

@mixin gradient-bg($color: null) {
  background-color: $color;

  @if $enable-gradients {
    background-image: var(--#{$variable-prefix}gradient);
  }
}
// Horizontal gradient, from left to right
//
// Creates two color stops, start and end, by specifying a color and position for each color stop.
@mixin gradient-x($start-color: $gray-700, $end-color: $gray-800, $start-percent: 0%, $end-percent: 100%) {
  background-image: linear-gradient(to right, $start-color $start-percent, $end-color $end-percent);
}

// Vertical gradient, from top to bottom
//
// Creates two color stops, start and end, by specifying a color and position for each color stop.
@mixin gradient-y($start-color: $gray-700, $end-color: $gray-800, $start-percent: null, $end-percent: null) {
  background-image: linear-gradient(to bottom, $start-color $start-percent, $end-color $end-percent);
}

@mixin gradient-directional($start-color: $gray-700, $end-color: $gray-800, $deg: 45deg) {
  background-image: linear-gradient($deg, $start-color, $end-color);
}

@mixin gradient-x-three-colors($start-color: $blue, $mid-color: $purple, $color-stop: 50%, $end-color: $red) {
  background-image: linear-gradient(to right, $start-color, $mid-color $color-stop, $end-color);
}

@mixin gradient-y-three-colors($start-color: $blue, $mid-color: $purple, $color-stop: 50%, $end-color: $red) {
  background-image: linear-gradient($start-color, $mid-color $color-stop, $end-color);
}

@mixin gradient-radial($inner-color: $gray-700, $outer-color: $gray-800) {
  background-image: radial-gradient(circle, $inner-color, $outer-color);
}

@mixin gradient-striped($color: rgba($white, .15), $angle: 45deg) {
  background-image: linear-gradient($angle, $color 25%, transparent 25%, transparent 50%, $color 50%, $color 75%, transparent 75%, transparent);
}

@mixin gradient($color, $value) {
  background-color: var(--#{$variable-prefix}#{$color}, map-get($value, "stop"));
  background-image: linear-gradient(45deg, var(--#{$variable-prefix}#{$color}-start, map-get($value, "start")) 0%, var(--#{$variable-prefix}#{$color}-stop, map-get($value, "stop") 100%));
}

Utilities API

Background utilities are declared in our utilities API in scss/_utilities.scss. Learn how to use the utilities API.

    "background-color": (
      property: background-color,
      class: bg,
      values: map-merge(
        $theme-colors,
        (
          "body": $body-bg,
          "white": $white,
          "transparent": transparent
        )
      ),
      vars: true
    ),