Bootstrap/site/content/docs/5.3/utilities/api.md

layout	title	description	group	aliases	toc
docs	Utility API	The utility API is a Sass-based tool to generate utility classes.	utilities	/docs/5.3/utilities/	true

Bootstrap utilities are generated with our utility API and can be used to modify or extend our default set of utility classes via Sass. Our utility API is based on a series of Sass maps and functions for generating families of classes with various options. If you're unfamiliar with Sass maps, read up on the official Sass docs to get started.

The $utilities map contains all our utilities and is later merged with your custom $utilities map, if present. The utility map contains a keyed list of utility groups which accept the following options:

{{< bs-table "table table-utilities" >}}

Option	Type	Default value	Description
property	Required	–	Name of the property, this can be a string or an array of strings (e.g., horizontal paddings or margins).
values	Required	–	List of values, or a map if you don't want the class name to be the same as the value. If null is used as map key, class is not prepended to the class name.
class	Optional	null	Name of the generated class. If not provided and property is an array of strings, class will default to the first element of the property array. If not provided and property is a string, the values keys are used for the class names.
css-var	Optional	false	Boolean to generate CSS variables instead of CSS rules.
css-variable-name	Optional	null	Custom un-prefixed name for the CSS variable inside the ruleset.
local-vars	Optional	null	Map of local CSS variables to generate in addition to the CSS rules.
state	Optional	null	List of pseudo-class variants (e.g., :hover or :focus) to generate.
responsive	Optional	false	Boolean indicating if responsive classes should be generated.
rfs	Optional	false	Boolean to enable [fluid rescaling with RFS]({{< docsref "/getting-started/rfs" >}}).
print	Optional	false	Boolean indicating if print classes need to be generated.
rtl	Optional	true	Boolean indicating if utility should be kept in RTL.
{{< /bs-table >}}

API explained

All utility variables are added to the $utilities variable within our _utilities.scss stylesheet. Each group of utilities looks something like this:

$utilities: (
  "opacity": (
    property: opacity,
    values: (
      0: 0,
      25: .25,
      50: .5,
      75: .75,
      100: 1,
    )
  )
);

Which outputs the following:

.opacity-0 { opacity: 0; }
.opacity-25 { opacity: .25; }
.opacity-50 { opacity: .5; }
.opacity-75 { opacity: .75; }
.opacity-100 { opacity: 1; }

Property

The required property key must be set for any utility, and it must contain a valid CSS property. This property is used in the generated utility's ruleset. When the class key is omitted, it also serves as the default class name. Consider the text-decoration utility:

$utilities: (
  "text-decoration": (
    property: text-decoration,
    values: none underline line-through
  )
);

Output:

.text-decoration-none { text-decoration: none !important; }
.text-decoration-underline { text-decoration: underline !important; }
.text-decoration-line-through { text-decoration: line-through !important; }

Values

Use the values key to specify which values for the specified property should be used in the generated class names and rules. Can be a list or map (set in the utilities or in a Sass variable).

As a list, like with [text-decoration utilities]({{< docsref "/utilities/text#text-decoration" >}}):

values: none underline line-through

As a map, like with [opacity utilities]({{< docsref "/utilities/opacity" >}}):

values: (
  0: 0,
  25: .25,
  50: .5,
  75: .75,
  100: 1,
)

As a Sass variable that sets the list or map, as in our [position utilities]({{< docsref "/utilities/position" >}}):

values: $position-values

Class

Use the class option to change the class prefix used in the compiled CSS. For example, to change from .opacity-* to .o-*:

$utilities: (
  "opacity": (
    property: opacity,
    class: o,
    values: (
      0: 0,
      25: .25,
      50: .5,
      75: .75,
      100: 1,
    )
  )
);

Output:

.o-0 { opacity: 0 !important; }
.o-25 { opacity: .25 !important; }
.o-50 { opacity: .5 !important; }
.o-75 { opacity: .75 !important; }
.o-100 { opacity: 1 !important; }

If class: null, generates classes for each of the values keys:

$utilities: (
  "visibility": (
    property: visibility,
    class: null,
    values: (
      visible: visible,
      invisible: hidden,
    )
  )
);

Output:

.visible { visibility: visible !important; }
.invisible { visibility: hidden !important; }

CSS variable utilities

Set the css-var boolean option to true and the API will generate local CSS variables for the given selector instead of the usual property: value rules. Add an optional css-variable-name to set a different CSS variable name than the class name.

Consider our .text-opacity-* utilities. If we add the css-variable-name option, we'll get a custom output.

$utilities: (
  "text-opacity": (
    css-var: true,
    css-variable-name: text-alpha,
    class: text-opacity,
    values: (
      25: .25,
      50: .5,
      75: .75,
      100: 1
    )
  ),
);

Output:

.text-opacity-25 { --bs-text-alpha: .25; }
.text-opacity-50 { --bs-text-alpha: .5; }
.text-opacity-75 { --bs-text-alpha: .75; }
.text-opacity-100 { --bs-text-alpha: 1; }

Local CSS variables

Use the local-vars option to specify a Sass map that will generate local CSS variables within the utility class's ruleset. Please note that it may require additional work to consume those local CSS variables in the generated CSS rules. For example, consider our .bg-* utilities:

$utilities: (
  "background-color": (
    property: background-color,
    class: bg,
    local-vars: (
      "bg-opacity": 1
    ),
    values: map-merge(
      $utilities-bg-colors,
      (
        "transparent": transparent
      )
    )
  )
);

Output:

.bg-primary {
  --bs-bg-opacity: 1;
  background-color: rgba(var(--bs-primary-rgb), var(--bs-bg-opacity)) !important;
}

States

Use the state option to generate pseudo-class variations. Example pseudo-classes are :hover and :focus. When a list of states are provided, classnames are created for that pseudo-class. For example, to change opacity on hover, add state: hover and you'll get .opacity-hover:hover in your compiled CSS.

Need multiple pseudo-classes? Use a space-separated list of states: state: hover focus.

$utilities: (
  "opacity": (
    property: opacity,
    class: opacity,
    state: hover,
    values: (
      0: 0,
      25: .25,
      50: .5,
      75: .75,
      100: 1,
    )
  )
);

Output:

.opacity-0-hover:hover { opacity: 0 !important; }
.opacity-25-hover:hover { opacity: .25 !important; }
.opacity-50-hover:hover { opacity: .5 !important; }
.opacity-75-hover:hover { opacity: .75 !important; }
.opacity-100-hover:hover { opacity: 1 !important; }

Responsive

Add the responsive boolean to generate responsive utilities (e.g., .opacity-md-25) across [all breakpoints]({{< docsref "/layout/breakpoints" >}}).

$utilities: (
  "opacity": (
    property: opacity,
    responsive: true,
    values: (
      0: 0,
      25: .25,
      50: .5,
      75: .75,
      100: 1,
    )
  )
);

Output:

.opacity-0 { opacity: 0 !important; }
.opacity-25 { opacity: .25 !important; }
.opacity-50 { opacity: .5 !important; }
.opacity-75 { opacity: .75 !important; }
.opacity-100 { opacity: 1 !important; }

@media (min-width: 576px) {
  .opacity-sm-0 { opacity: 0 !important; }
  .opacity-sm-25 { opacity: .25 !important; }
  .opacity-sm-50 { opacity: .5 !important; }
  .opacity-sm-75 { opacity: .75 !important; }
  .opacity-sm-100 { opacity: 1 !important; }
}

@media (min-width: 768px) {
  .opacity-md-0 { opacity: 0 !important; }
  .opacity-md-25 { opacity: .25 !important; }
  .opacity-md-50 { opacity: .5 !important; }
  .opacity-md-75 { opacity: .75 !important; }
  .opacity-md-100 { opacity: 1 !important; }
}

@media (min-width: 992px) {
  .opacity-lg-0 { opacity: 0 !important; }
  .opacity-lg-25 { opacity: .25 !important; }
  .opacity-lg-50 { opacity: .5 !important; }
  .opacity-lg-75 { opacity: .75 !important; }
  .opacity-lg-100 { opacity: 1 !important; }
}

@media (min-width: 1200px) {
  .opacity-xl-0 { opacity: 0 !important; }
  .opacity-xl-25 { opacity: .25 !important; }
  .opacity-xl-50 { opacity: .5 !important; }
  .opacity-xl-75 { opacity: .75 !important; }
  .opacity-xl-100 { opacity: 1 !important; }
}

@media (min-width: 1400px) {
  .opacity-xxl-0 { opacity: 0 !important; }
  .opacity-xxl-25 { opacity: .25 !important; }
  .opacity-xxl-50 { opacity: .5 !important; }
  .opacity-xxl-75 { opacity: .75 !important; }
  .opacity-xxl-100 { opacity: 1 !important; }
}

Print

Enabling the print option will also generate utility classes for print, which are only applied within the @media print { ... } media query.

$utilities: (
  "opacity": (
    property: opacity,
    print: true,
    values: (
      0: 0,
      25: .25,
      50: .5,
      75: .75,
      100: 1,
    )
  )
);

Output:

.opacity-0 { opacity: 0 !important; }
.opacity-25 { opacity: .25 !important; }
.opacity-50 { opacity: .5 !important; }
.opacity-75 { opacity: .75 !important; }
.opacity-100 { opacity: 1 !important; }

@media print {
  .opacity-print-0 { opacity: 0 !important; }
  .opacity-print-25 { opacity: .25 !important; }
  .opacity-print-50 { opacity: .5 !important; }
  .opacity-print-75 { opacity: .75 !important; }
  .opacity-print-100 { opacity: 1 !important; }
}

Importance

All utilities generated by the API include !important to ensure they override components and modifier classes as intended. You can toggle this setting globally with the $enable-important-utilities variable (defaults to true).

Using the API

Now that you're familiar with how the utilities API works, learn how to add your own custom classes and modify our default utilities. There are two ways you can do this:

1. If you only need to override our default utilities or add new ones, we'll merge your $utilities variable with ours
2. If you require more fine grained control, we provide mixins to let you update our default utilities configuration.

You may also want to refer to some of the utilities configuration in your Sass code, for which we provide some handy functions.

Adding or overriding utilities

Override existing utilities by using the same key. For example, if you want additional responsive overflow utility classes, you can do this:

$utilities: (
  "overflow": (
    responsive: true,
    property: overflow,
    values: visible hidden scroll auto,
  ),
);

@import 'bootstrap/scss/utilities';
@import 'bootstrap/scss/utilities/api';

Modifying our defaults

After importing bootstrap/scss/utilities, you can use mixins to:

• add or remove utilities
• update utilities options, like responsive, class, rtl...
• add, remove or update utility values

Adding and removing utilities

utilities-add and utilities-remove mixins let you add and remove utilities from the configuration. Adding an existing utility will completely override it.

@import "bootstrap/scss/functions";
@import "bootstrap/scss/variables";
@import "bootstrap/scss/variables-dark";
@import "bootstrap/scss/maps";
@import "bootstrap/scss/mixins";
@import "bootstrap/scss/utilities";

@include utilities-add(cursor, (
  property: cursor,
  class: cursor,
  responsive: true,
  values: auto pointer grab,
));

// Remove user-select and shadow
@include utilities-remove(user-select, shadow);

@import "bootstrap/scss/utilities/api";

Updating utility options

utilities-set-option and utilities-set-options let you configure one or several options of a utility. utilities-set-options will merge the new options with the existing ones by default, but you can provide a third $merge: false argument to completely override them.

And if the utility does not exist, both mixins will create a new one.

@import "bootstrap/scss/functions";
@import "bootstrap/scss/variables";
@import "bootstrap/scss/variables-dark";
@import "bootstrap/scss/maps";
@import "bootstrap/scss/mixins";
@import "bootstrap/scss/utilities";

// Let's make the overflow utility responsive
@include utilities-set-option(overflow, responsive, true);

// Or revert the class for the margin-start utilities to their v4 values
@include utilities-set-option(margin-start, class, ml);

// Let's make line-height responsive and override its values
@include utilities-set-options(line-height, (
  responsive: true,
  values: (
    1: 1,
    1.25: 1.25,
    1.5: 1.5
    inherit: inherit
  )
));

@import 'bootstrap/scss/utilities/api';

Updating utility values

If you want to keep most of the default values for a utility, and just add, remove or update a few, replacing the values option can be a bit of a burden to maintain. utilities-add-values and utilities-remove-values mixins will help you make these targeted updates.

@import "bootstrap/scss/functions";
@import "bootstrap/scss/variables";
@import "bootstrap/scss/variables-dark";
@import "bootstrap/scss/maps";
@import "bootstrap/scss/mixins";

@import 'bootstrap/scss/utilities';

// Let's add a few new values to the `flex` utility
@include utilities-add-values(flex, (
  none: none,
  auto: auto
));

// And remove the row-reverse and column-reverse from flex-direction
@include utilities-remove-values(flex-direction, row-reverse, column-reverse);

@import 'bootstrap/scss/utilities/api';

Practical examples

Enable responsive

You can enable responsive classes for an existing set of utilities that are not currently responsive by default. For example, to make the border classes responsive:

@import "bootstrap/scss/functions";
@import "bootstrap/scss/variables";
@import "bootstrap/scss/variables-dark";
@import "bootstrap/scss/maps";
@import "bootstrap/scss/mixins";

@import "bootstrap/scss/utilities";

@include utilities-set-option(border, responsive, true);

@import "bootstrap/scss/utilities/api";

Rename utilities

Missing v4 utilities, or used to another naming convention? The utilities API can be used to override the resulting class of a given utility—for example, to rename .ms-* utilities to oldish .ml-*:

@import "bootstrap/scss/functions";
@import "bootstrap/scss/variables";
@import "bootstrap/scss/variables-dark";
@import "bootstrap/scss/maps";
@import "bootstrap/scss/mixins";

@import "bootstrap/scss/utilities";

@include utilities-set-option(margin-start, class, ml);

@import "bootstrap/scss/utilities/api";

Remove utility in RTL

Some edge cases make RTL styling difficult, such as line breaks in Arabic. Thus utilities can be dropped from RTL output by setting the rtl option to false:

@import "bootstrap/scss/functions";
@import "bootstrap/scss/variables";
@import "bootstrap/scss/variables-dark";
@import "bootstrap/scss/maps";
@import "bootstrap/scss/mixins";

@import "bootstrap/scss/utilities";

@include utilities-set-option(word-wrap, rtl, false);

@import "bootstrap/scss/utilities/api";

Output:

/* rtl:begin:remove */
.text-break {
  word-wrap: break-word !important;
  word-break: break-word !important;
}
/* rtl:end:remove */

This doesn't output anything in RTL, thanks to the RTLCSS remove control directive.

Referring to the utilities configuration

The utilities-get-value function let your grab a specific value of a utility. This can help you run some computations with it, either in Sass or with calc(). It also lets you access values that can be tweaked by other utilities, (like how bg, text and border can be tweaked by bg-opacity, text-opacity or border-opacity respectively).

@import "bootstrap/scss/functions";
@import "bootstrap/scss/variables";
@import "bootstrap/scss/variables-dark";
@import "bootstrap/scss/maps";
@import "bootstrap/scss/mixins";

@import "bootstrap/scss/utilities";

// The box will be configurable with the bg-opacity and text-opacity classes
.box {
  border: utilities-get-value(border, null);
  padding: map-get($spacers, 3);
  background: utilities-get-value(background-color, body);
  color: utilities-get-value(color, body);
}

This is likely the function you'll use the most, but you can also:

• access all the values of a utility with utilities-get-values, which will always return a map to simplify their processing
• access a specific option with utilities-get-option
• or even all the options with utilities-get-options