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](https://sass-lang.com/documentation/values/maps) 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:
| `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. |
| `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]({{< docsref "/getting-started/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. |
All utility variables are added to the `$utilities` variable within our `_utilities.scss` stylesheet. Each group of utilities looks something like this:
Use the `state` option to generate pseudo-class variations. Example pseudo-classes are `:hover` and `:focus`. When a list of states are provided, classnames are created for that pseudo-class. For example, to change opacity on hover, add `state: hover` and you'll get `.opacity-hover:hover` in your compiled CSS.
Need multiple pseudo-classes? Use a space-separated list of states: `state: hover focus`.
All utilities generated by the API include `!important` to ensure they override components and modifier classes as intended. You can toggle this setting globally with the `$enable-important-utilities` variable (defaults to `true`).
New utilities can be added to the default `$utilities` map with a `map-merge`. Make sure our required Sass files and `_utilities.scss` are imported first, then use the `map-merge` to add your additional utilities. For example, here's how to add a responsive `cursor` utility with three values.
Modify existing utilities in the default `$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.
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:
```scss
@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:
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-*`:
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.
Some edge cases make [RTL styling difficult](https://rtlstyling.com/posts/rtl-styling#common-things-that-might-not-work-for-rtl), such as line breaks in Arabic. Thus utilities can be dropped from RTL output by setting the `rtl` option to `false`:
```scss
$utilities: (
"word-wrap": (
property: word-wrap word-break,
class: text,
values: (break: break-word),
rtl: false
),
);
```
Output:
```css
/* 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](https://rtlcss.com/learn/usage-guide/control-directives/#remove).
