Utility API
The utility API is a Sass-based tool to generate utility classes.
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:
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. |
Optional | false | Boolean indicating if print classes need to be generated. | |
rtl | Optional | true | Boolean indicating if utility should be kept in RTL. |
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:
values: none underline line-through
As a map, like with opacity utilities:
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:
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.
$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; }
}
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.
Override 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,
),
);
Add utilities
New utilities can be added to the default $utilities
map with a map-merge
. Make sure our required Sass files and _utilities.scss
are imported first, then use the map-merge
to add your additional utilities. For example, here’s how to add a responsive cursor
utility with three values.
@import "bootstrap/scss/functions";
@import "bootstrap/scss/variables";
@import "bootstrap/scss/maps";
@import "bootstrap/scss/mixins";
@import "bootstrap/scss/utilities";
$utilities: map-merge(
$utilities,
(
"cursor": (
property: cursor,
class: cursor,
responsive: true,
values: auto pointer grab,
)
)
);
@import "bootstrap/scss/utilities/api";
Modify utilities
Modify existing utilities in the default $utilities
map with map-get
and map-merge
functions. In the example below, we’re adding an additional value to the width
utilities. Start with an initial map-merge
and then specify which utility you want to modify. From there, fetch the nested "width"
map with map-get
to access and modify the utility’s options and values.
@import "bootstrap/scss/functions";
@import "bootstrap/scss/variables";
@import "bootstrap/scss/maps";
@import "bootstrap/scss/mixins";
@import "bootstrap/scss/utilities";
$utilities: map-merge(
$utilities,
(
"width": map-merge(
map-get($utilities, "width"),
(
values: map-merge(
map-get(map-get($utilities, "width"), "values"),
(10: 10%),
),
),
),
)
);
@import "bootstrap/scss/utilities/api";
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/maps";
@import "bootstrap/scss/mixins";
@import "bootstrap/scss/utilities";
$utilities: map-merge(
$utilities, (
"border": map-merge(
map-get($utilities, "border"),
( responsive: true ),
),
)
);
@import "bootstrap/scss/utilities/api";
This will now generate responsive variations of .border
and .border-0
for each breakpoint. Your generated CSS will look like this:
.border { ... }
.border-0 { ... }
@media (min-width: 576px) {
.border-sm { ... }
.border-sm-0 { ... }
}
@media (min-width: 768px) {
.border-md { ... }
.border-md-0 { ... }
}
@media (min-width: 992px) {
.border-lg { ... }
.border-lg-0 { ... }
}
@media (min-width: 1200px) {
.border-xl { ... }
.border-xl-0 { ... }
}
@media (min-width: 1400px) {
.border-xxl { ... }
.border-xxl-0 { ... }
}
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/maps";
@import "bootstrap/scss/mixins";
@import "bootstrap/scss/utilities";
$utilities: map-merge(
$utilities, (
"margin-start": map-merge(
map-get($utilities, "margin-start"),
( class: ml ),
),
)
);
@import "bootstrap/scss/utilities/api";
Remove utilities
Remove any of the default utilities with the map-remove() Sass function.
@import "bootstrap/scss/functions";
@import "bootstrap/scss/variables";
@import "bootstrap/scss/maps";
@import "bootstrap/scss/mixins";
@import "bootstrap/scss/utilities";
// Remove multiple utilities with a comma-separated list
$utilities: map-remove($utilities, "width", "float");
@import "bootstrap/scss/utilities/api";
You can also use the map-merge() Sass function and set the group key to null
to remove the utility.
@import "bootstrap/scss/functions";
@import "bootstrap/scss/variables";
@import "bootstrap/scss/maps";
@import "bootstrap/scss/mixins";
@import "bootstrap/scss/utilities";
$utilities: map-merge(
$utilities,
(
"width": null
)
);
@import "bootstrap/scss/utilities/api";
Add, remove, modify
You can add, remove, and modify many utilities all at once with the map-merge() Sass function. Here’s how you can combine the previous examples into one larger map.
@import "bootstrap/scss/functions";
@import "bootstrap/scss/variables";
@import "bootstrap/scss/maps";
@import "bootstrap/scss/mixins";
@import "bootstrap/scss/utilities";
$utilities: map-merge(
$utilities,
(
// Remove the `width` utility
"width": null,
// Make an existing utility responsive
"border": map-merge(
map-get($utilities, "border"),
( responsive: true ),
),
// Add new utilities
"cursor": (
property: cursor,
class: cursor,
responsive: true,
values: auto pointer grab,
)
)
);
@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
:
$utilities: (
"word-wrap": (
property: word-wrap word-break,
class: text,
values: (break: break-word),
rtl: false
),
);
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.