--- layout: docs title: Background description: Convey meaning through `background-color` and add decoration with gradients. group: utilities toc: true --- {{< callout info >}} {{< partial "callouts/warning-color-assistive-technologies.md" >}} {{< /callout >}} ## 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]({{< docsref "/utilities/colors" >}}). {{< callout info >}} Background utilities like `.bg-*` that generated from our original `$theme-colors` Sass map don't yet respond to color modes, however, any `.bg-*-subtle` utility will. This will be resolved in v6. {{< /callout >}} {{< example >}} {{< colors.inline >}} {{- range (index $.Site.Data "theme-colors") }}
.bg-{{ .name }}
.bg-{{ .name }}-subtle
{{- end -}} {{< /colors.inline >}}
.bg-body-secondary
.bg-body-tertiary
.bg-body
.bg-black
.bg-white
.bg-transparent
{{< /example >}} ## 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(--bs-gradient);`. {{< markdown >}} {{< colors.inline >}} {{- range (index $.Site.Data "theme-colors") }}
.bg-{{ .name }}.bg-gradient
{{- end -}} {{< /colors.inline >}}
.bg-black.bg-gradient
{{< /markdown >}} ## Opacity {{< added-in "5.1.0" >}} As of v5.1.0, `background-color` utilities are generated with Sass using CSS variables. This allows for real-time color changes without compilation and dynamic alpha transparency changes. ### How it works Consider our default `.bg-success` utility. ```css .bg-success { --bs-bg-opacity: 1; background-color: rgba(var(--bs-success-rgb), var(--bs-bg-opacity)) !important; } ``` We use an RGB version of our `--bs-success` (with the value of `25, 135, 84`) CSS variable and attached a second CSS variable, `--bs-bg-opacity`, for the alpha transparency (with a default value `1` thanks to a local CSS variable). That means anytime you use `.bg-success` now, your computed `color` value is `rgba(25, 135, 84, 1)`. The local CSS variable inside each `.bg-*` class avoids inheritance issues so nested instances of the utilities don't automatically have a modified alpha transparency. ### Example To change that opacity, override `--bs-bg-opacity` via custom styles or inline styles. {{< example >}}
This is default success background
This is 50% opacity success background
{{< /example >}} Or, choose from any of the `.bg-opacity` utilities: {{< example >}}
This is default success background
This is 75% opacity success background
This is 50% opacity success background
This is 25% opacity success background
This is 10% opacity success background
{{< /example >}} ## CSS In addition to the following Sass functionality, consider reading about our included [CSS custom properties]({{< docsref "/customize/css-variables" >}}) (aka CSS variables) for colors and more. ### Sass variables Most `background-color` utilities are generated by our theme colors, reassigned from our generic color palette variables. {{< scss-docs name="color-variables" file="scss/_variables.scss" >}} {{< scss-docs name="theme-color-variables" file="scss/_variables.scss" >}} {{< scss-docs name="variable-gradient" file="scss/_variables.scss" >}} Grayscale colors are also available, but only a subset are used to generate any utilities. {{< scss-docs name="gray-color-variables" file="scss/_variables.scss" >}} Variables for setting `background-color` in `.bg-*-subtle` utilities in light and dark mode: {{< scss-docs name="theme-bg-subtle-variables" file="scss/_variables.scss" >}} {{< scss-docs name="theme-bg-subtle-dark-variables" file="scss/_variables-dark.scss" >}} ### Sass maps Theme colors are then put into a Sass map so we can loop over them to generate our utilities, component modifiers, and more. {{< scss-docs name="theme-colors-map" file="scss/_variables.scss" >}} Grayscale colors are also available as a Sass map. **This map is not used to generate any utilities.** {{< scss-docs name="gray-colors-map" file="scss/_variables.scss" >}} RGB colors are generated from a separate Sass map: {{< scss-docs name="theme-colors-rgb" file="scss/_maps.scss" >}} Background color opacities build on that with their own map that's consumed by the utilities API: {{< scss-docs name="utilities-bg-colors" file="scss/_maps.scss" >}} Color mode background colors are also available as a Sass map: {{< scss-docs name="theme-bg-subtle-map" file="scss/_maps.scss" >}} {{< scss-docs name="theme-bg-subtle-dark-map" file="scss/_maps.scss" >}} ### Sass 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. {{< scss-docs name="gradient-bg-mixin" file="scss/mixins/_gradients.scss" >}} {{< scss-docs name="gradient-mixins" file="scss/mixins/_gradients.scss" >}} ### Sass utilities API Background utilities are declared in our utilities API in `scss/_utilities.scss`. [Learn how to use the utilities API.]({{< docsref "/utilities/api#using-the-api" >}}) {{< scss-docs name="utils-bg-color" file="scss/_utilities.scss" >}}