layout: docs title: Utility API description: The utility API is a Sass-based tool to generate utility classes. group: utilities aliases: "/docs/5.0/utilities/"
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 text-start" >}}
| Option | Type | 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, it isn't compiled. |
| class
| Optional | Variable for the class name if you don't want it to be the same as the property. In case you don't provide the class
key and property
key is an array of strings, the class name will be the first element of the property
array. |
| state
| Optional | List of pseudo-class variants like :hover
or :focus
to generate for the utility. No default value. |
| responsive
| Optional | Boolean indicating if responsive classes need to be generated. false
by default. |
| rfs
| Optional | Boolean to enable fluid rescaling. Have a look at the RFS page to find out how this works. false
by default. |
| print
| Optional | Boolean indicating if print classes need to be generated. false
by default. |
| rtl
| Optional | Boolean indicating if utility should be kept in RTL. true
by default. |
{{< /bs-table >}}
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; }
Use the class
option to change the class prefix used in the compiled CSS:
$utilities: (
"opacity": (
property: opacity,
class: o,
values: (
0: 0,
25: .25,
50: .5,
75: .75,
100: 1,
)
)
);
Output:
.o-0 { opacity: 0; }
.o-25 { opacity: .25; }
.o-50 { opacity: .5; }
.o-75 { opacity: .75; }
.o-100 { opacity: 1; }
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; }
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; }
}
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,
),
);
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; }
}
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
).
Now that you're familiar with how the utilities API works, learn how to add your own custom classes and modify our default 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/utilities";
$utilities: map-merge(
$utilities,
(
"cursor": (
property: cursor,
class: cursor,
responsive: true,
values: auto pointer grab,
)
)
);
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/utilities";
$utilities: map-merge(
$utilities,
(
"width": map-merge(
map-get($utilities, "width"),
(
values: map-merge(
map-get(map-get($utilities, "width"), "values"),
(10: 10%),
),
),
),
)
);
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/utilities";
$utilities: map-merge(
$utilities, (
"border": map-merge(
map-get($utilities, "border"),
( responsive: true ),
),
)
);
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 { ... }
}
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/utilities";
$utilities: map-merge(
$utilities, (
"margin-start": map-merge(
map-get($utilities, "margin-start"),
( class: ml ),
),
)
);
Remove any of the default utilities by setting the group key to null
. For example, to remove all our width
utilities, create a $utilities
map-merge
and add "width": null
within.
@import "bootstrap/scss/functions";
@import "bootstrap/scss/variables";
@import "bootstrap/scss/utilities";
$utilities: map-merge(
$utilities,
(
"width": null
)
);
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.