Using CSS variables in Bootstrap

@mdo May 16, 2022

Bootstrap v5.2.0-beta1 added a slew of CSS custom properties, or CSS variables, across the :root level and all our core components. Here’s a quick look at how you can utilize them in your projects.

With CSS variables, you can now customize Bootstrap easier than ever, and without the need for a CSS preprocessor. All the power of Sass is still there behind the scenes, but CSS variables adds a ton of power for the future. Use and compose new values, updates styles globally without recompiling, set fallback values, setup new color modes, and more.

Let’s dig in.

CSS variables?

Their official name is custom properties, but they’re often referred to as CSS variables thanks to their most immediate use case for setting specific values. Consider reading the MDN CSS custom properties article or the CSS Tricks guide if you need a primer.

In a nutshell, CSS variables allow you to name frequently used values. For example, instead of writing #6f42c1 everywhere, you can set --purple: #6f42c1. Then you can use that variable later on with the var() function.

:root {
  --purple: #6f42c1;
.custom-element {
  color: var(--purple);

We use CSS variables in Bootstrap to set many property values globally, across our components, and in some of our utilities.

Groups of variables

When we talk about CSS variables in Bootstrap, we’re referring to three major groups:

  • Root variables — Globally scoped variables available on the :root element (<html> usually) and accessible by any element throughout the DOM.

  • Component variables — Variables scoped specifically to each component, usually on the component’s base class, and their modifier classes and Sass mixins.

  • Utility variables — Used as modifiers within other utility classes.

Regardless of where they are, all of our CSS variables are prefixed with --bs-, so you know where they’re coming from and how they might be used across codebases that mix Bootstrap’s CSS with additional custom styles. You’ll also notice that we don’t put all our component variables at the root level. This keeps CSS variables scoped to their intended use cases and prevents polluted variables in the global :root scope.

It’s also worth mentioning two larger efforts that are still to come around CSS variables:

  1. Adding CSS variables to all our forms
  2. Adding more nuanced global theme variables and support for color modes like dark mode.

These are likely coming in v5.3.0 (our next minor release after v5.2.0 stablizes), so in the mean time, check out the GitHub repo to see how things are shaping up.

Root variables

Root variables in web inspector

Bootstrap has a ton of root variables and we’ll only be adding more in future updates for the aforementioned color mode support. As of this post, we have the following CSS variables on the :root element:

  • Colors — All named colors, gray colors, and theme colors. This also includes all our $theme-colors in their rgb format.

  • Body font styles — Everything from font-size to color and more, all applied to our <body> element.

  • Shared properties — For property-value pairings that we consider theme specific, like link colors and border styles.

Root CSS variables are used extensively across other parts of Bootstrap to allow you to easily override our default styles at a global level. For example, if you wanted to adjust the default border-radius and link color for our components, you could override a couple variables instead of writing new selectors.

// custom.css
:root {
  --bs-border-radius: .5rem;
  --bs-link-color: #333;

You can even use other root variables to override those values:

// custom.css
:root {
  --bs-border-radius: var(--bs-border-radius-lg);
  --bs-link-color: var(--bs-gray-800);

Without CSS variables, you’d have to use a preprocessor like Sass or write new selectors for every instance of these properties across all components. The former is relatively easy, the latter not so much. CSS variables help solve that.

Component variables

On our components, CSS variables get even more power for customizing. Nearly everything under the Components section in our docs sidebar now has CSS variables available to you:

Scrollspy and close button have no relevant CSS variables, so they’re excluded here.

Throughout our documentation you’ll find examples of customizing our default components by overriding their CSS variables. One great example comes from our own docs where we write our own button styles to create a purple button.

.btn-bd-primary {
  --bs-btn-font-weight: 600;
  --bs-btn-color: var(--bs-white);
  --bs-btn-bg: var(--bd-violet);
  --bs-btn-border-color: var(--bd-violet);
  --bs-btn-border-radius: .5rem;
  --bs-btn-hover-color: var(--bs-white);
  --bs-btn-hover-bg: #{shade-color($bd-violet, 10%)};
  --bs-btn-hover-border-color: #{shade-color($bd-violet, 10%)};
  --bs-btn-focus-shadow-rgb: var(--bd-violet-rgb);
  --bs-btn-active-color: var(--bs-btn-hover-color);
  --bs-btn-active-bg: #{shade-color($bd-violet, 20%)};
  --bs-btn-active-border-color: #{shade-color($bd-violet, 20%)};

Which looks like this:

Custom Bootstrap docs button

Another great example is from our tooltips. You can add custom classes to tooltips and popovers in Bootstrap with data-bs-custom-class="custom-tooltip". Then, with one CSS variable, you can change the tooltip background and arrow color.

.custom-tooltip {
  --bs-tooltip-bg: var(--bs-primary);

Which looks like this:

Custom tooltip

There are dozens of CSS variables in play across our components. All of them are referenced in a new section on the relevant docs page. For example, here are our modal CSS variables. This is in addition to all the Sass variables, mixins, loops, and maps used for each component.

Utility variables

Not every utility class uses CSS variables, but the ones that do gain a good amount of power and customization. Background, border, and color utilities all have what we call “local CSS variables” to improve their usefulness. Each of them uses CSS variables to customize the alpha transparency value of rgba() colors.

Consider our background color utilities, .bg-*. By default each utility class has a local variable, --bs-bg-opacity with a default value of 1. To change the background utility alpha value, you can override that value with your own styles, or some new .bg-opacity-* utilities.

<div class="p-3 bg-success bg-opacity-25">

Here’s how .bg-success looks with all our .bg-opacity-* classes applied:

Background opacity examples

And the same is available for border color opacity (--bs-border-opacity and .border-opacity-*) and text color opacity (--bs-text-opacity and .text-opacity-*). So many color options are now available with these utilities.

By default, we ship with five values for these various opacity utilities.

Class names Alpha value

Expect more CSS variables to make their way into our utilities. There’s a lot of power in real-time customization, even for what we consider immutable styles.

Ready to get started with Bootstrap? Checkout the quick start guide so you can put these new CSS variables to work in your next project!

Bootstrap Icons v1.8.2

@mdo May 13, 2022

Bootstrap Icons v1.8.2 has arrived with some bug fixes and a refreshed docs design to match our main project.

Here’s a quick rundown on the icon fixes:

  • Fix cutoff bank icon
  • Fix house-heart and house-heart-fill fill-rules
  • Fix corners of pentagon icons to match other shapes
  • Fix fill-rule for x-lg
  • Fix cutoff tool icon

On the CSS side, we’ve also added font-display: block to help address our icon font affecting Google Lighthouse scores.

Looking for more new icons? Head to the issue tracker to check for open requests or submit a new one.


To get started, install or update via npm:

npm i bootstrap-icons

Or Composer:

composer require twbs/bootstrap-icons

You can also download the release from GitHub, or download just the SVGs and fonts (without the rest of the repository files).


The Figma file is now published to the Figma Community! It’s the same Bootstrap Icons Figma file you’ve seen from previous releases, just a little more accessible to those using the app.

Bootstrap 5.2.0 beta

@mdo May 13, 2022

It’s the biggest release since v5 itself—Bootstrap v5.2.0-beta1 is here! This release features redesigned docs, CSS variables for all our components, responsive offcanvas, new helpers and utilities, refined buttons and inputs, and lots of improvements under the hood.

Given the size of the update and time since our last release, we’re doing something different and shipping it as a beta first. Keep reading for details.

Why so long?

I want to start by acknowledging the time it’s taken to ship a new release. As an open source maintainer, I’m constantly worried about not doing or being good enough of a developer for my projects. Pair that with a distributed team all working through this pandemic and me having a heart attack, we’ve all needed some down time. I managed to put together a Bootstrap Icons release with what energy I had before needing another break. The rest of the team has also needed some well deserved down time.

I ask that you all please take some time to send some appreciation and support to your favorite open source maintainers. Everyone could use a little more love in this work.

All that said, we’re shipping v5.2.0-beta1 first since it’s been so long—we’d love your help testing things out. We’ll follow up with a stable release as soon as possible.

Okay, now onto the good parts!

Redesigned docs

Another release, another docs refresh! From the get go, you’ll notice our Bootstrap Purple™ is much more vibrant now, making everything feel brand new. We’ve rewritten our entire homepage to better show off all the awesome features of Bootstrap.

New homepage

See the homepage in action and let us know what you think!

New docs page

Stepping into the actual docs, you’ll notice quite a few changes. We’ve streamlined our navbar, done away with our subnav, and changed the sidebar to always show every page link for greater discoverability. Show above is also our refreshed quick start guide, which is now a step-by-step instructional guide for using Bootstrap via CDN.

Docs version picker

The refreshed navbar also has a long-awaited new version picker for v5.2.0 and beyond. From any page, click the version and see options to navigate to previous minor releases of that same page. When a page doesn’t exist in an older release, you’ll see a disabled version in the dropdown. We currently have no plans to link pages across major versions.

New search

The docs search is now powered by the latest version of Algolia’s DocSearch, bringing an improved design that even shows your most recent searches.

Design tweaks

To coincide with our docs redesign, we’ve given our buttons and inputs a slight refresh with some refined border-radius values. It’s a small change, but a welcomed refresh to keep things modern and fresh. Here’s a look at the before and after of our buttons:

Updated buttons

And the before and after of our inputs:

Updated inputs

Component CSS variables

With this release, all our components now include CSS variables to enable real-time customization, easier theming, and (soon) color mode support starting with dark mode. Every component page has been updated to include a reference guide of the relevant CSS variables. Take for example our buttons:

--#{$prefix}btn-padding-x: #{$btn-padding-x};
--#{$prefix}btn-padding-y: #{$btn-padding-y};
--#{$prefix}btn-font-family: #{$btn-font-family};
@include rfs($btn-font-size, --#{$prefix}btn-font-size);
--#{$prefix}btn-font-weight: #{$btn-font-weight};
--#{$prefix}btn-line-height: #{$btn-line-height};
--#{$prefix}btn-color: #{$body-color};
--#{$prefix}btn-bg: transparent;
--#{$prefix}btn-border-width: #{$btn-border-width};
--#{$prefix}btn-border-color: transparent;
--#{$prefix}btn-border-radius: #{$btn-border-radius};
--#{$prefix}btn-box-shadow: #{$btn-box-shadow};
--#{$prefix}btn-disabled-opacity: #{$btn-disabled-opacity};
--#{$prefix}btn-focus-box-shadow: 0 0 0 #{$btn-focus-width} rgba(var(--#{$prefix}btn-focus-shadow-rgb), .5);

Values for virtually every CSS variables are assigned via Sass variable, so customization via CSS and Sass are both well supported. Also included for several components are examples of customizing via CSS variables.

Custom button

Check out all our components to see how you can customize them to your liking.

New _maps.scss

Bootstrap v5.2.0-beta1 introduces a new Sass file with _maps.scss that pulls out several Sass maps from _variables.scss to fix an issue where updates to an original map were not applied to secondary maps that extend it. It’s not ideal, but it resolves a longstanding issue for folks when working with customized maps.

For example, updates to $theme-colors were not being applied to other maps that relied on $theme-colors (like the $utilities-colors and more), which created broken customization workflows. To summarize the problem, Sass has a limitation where once a default variable or map has been used, it cannot be updated. There’s a similar shortcoming with CSS variables when they’re used to compose other CSS variables.

This is also why variable customizations in Bootstrap have to come after @import "functions";, but before @import "variables"; and the rest of our import stack. The same applies to Sass maps—you must override the defaults before they get used. The following maps have been moved to the new _maps.scss:

  • $theme-colors-rgb
  • $utilities-colors
  • $utilities-text
  • $utilities-text-colors
  • $utilities-bg
  • $utilities-bg-colors
  • $negative-spacers
  • $gutters

Your custom Bootstrap CSS builds should now look like this with a separate maps import.

  // Functions come first
  @import "functions";

  // Optional variable overrides here
+ $custom-color: #df711b;
+ $custom-theme-colors: (
+   "custom": $custom-color
+ );

  // Variables come next
  @import "variables";

+ // Optional Sass map overrides here
+ $theme-colors: map-merge($theme-colors, $custom-theme-colors);
+ // Followed by our default maps
+ @import "maps";
  // Rest of our imports
  @import "mixins";
  @import "utilities";
  @import "root";
  @import "reboot";
  // etc

New helpers and utilities

We’re continuing to invest in our helpers and utilities to make it easier to quickly build and modify custom components.

  • Added new .text-bg-{color} helpers. Instead of setting individual .text-* and .bg-* utilities, you can now use the .text-bg-* helpers to set a background-color with contrasting foreground color.

  • Expanded font-weight utilities to include .fw-semibold for semibold fonts.

  • Expanded border-radius utilities to include two new sizes, .rounded-4 and .rounded-5, for more options.

Expect more improvements here as v5’s development continues.

Responsive offcanvas

Our Offcanvas component now has responsive variations. The original .offcanvas class remains unchanged—it hides content across all viewports. To make it responsive, change that .offcanvas class to any .offcanvas-{sm|md|lg|xl|xxl} class.

And tons more!

  • Introduced new $enable-container-classes option. — Now when opting into the experimental CSS Grid layout, .container-* classes will still be compiled, unless this option is set to false. Containers also now keep their gutter values.

  • Thicker table dividers are now opt-in. — We’ve removed the thicker and more difficult to override border between table groups and moved it to an optional class you can apply, .table-group-divider. See the table docs for an example.

  • Scrollspy has been rewritten to use the Intersection Observer API, which means you no longer need relative parent wrappers, deprecates offset config, and more. Look for your Scrollspy implementations to be more accurate and consistent in their nav highlighting.

  • Added .form-check-reverse modifier to flip the order of labels and associated checkboxes/radios.

  • Added striped columns support to tables via the new .table-striped-columns class.

For a complete list of changes, see the project on GitHub.

Coming soon: Dark mode!

Much of the work we’ve done in v5.2.0-beta1 has been in support of adding dark mode to Bootstrap. Yes, it’s finally coming in our next minor release!

Dark mode

We’re adding tons of new global CSS variables, cleaning up docs styles, and better supporting overall customization. Some details and topics being worked on for dark mode:

  • Do we provide a JS plugin for toggling color modes? Right now we’re just building custom functionality for our docs.

  • Our current implementation is being built with data-theme selectors which allows explicit color mode switching (via user control vs and system preference) and custom color modes beyond light and dark.

  • We’re adding quite a few new colors outside $theme-colors to improve subtle UI customization. These are being implemented via :root and [data-theme="{theme}"] selectors for global use.

We’d love your feedback along the way, so check out the dark mode pull request and dark mode staging site to test it out.

Also coming in v5.3.0

There’s lots to look forward to in our next minor release, though we’ll likely have some bug fixes along the way.

And likely a lot more!

Get the release

Head to for the latest. It’s also been pushed to npm:

npm i bootstrap@v5.2.0-beta1

Read the GitHub v5.2.0-beta1 changelog for a complete list of changes in this release.

Support the team

Visit our Open Collective page or our team members’ GitHub profiles to help support the maintainers contributing to Bootstrap.

Bootstrap Icons v1.8.0

@mdo January 31, 2022

Bootstrap Icons v1.8.0 is here with over 140 new icons, including dozens of new heart icons ready for Valentine’s Day and dozens of filetype icons. We’re now at almost 1,700 icons and is once again our second largest release. Keep reading to see what’s new.

140+ new icons

Perfect for Valentine’s Day or any other time you need to show a little heart, there are dozens of icons to choose from.

New love icons in v1.8.0

Want to visually show the extensions of your files? There are tons of new options for programming languages, audio and video, images, and more.

New filetype icons in v1.8.0

Elsewhere we’ve expanded a number of other categories of icons. There are some new medical icons (more are planned), lots of new clipboard icons, additional tools, and more.

Miscellaneous new icons in v1.8.0

Looking for more new icons? Head to the issue tracker to check for open requests or submit a new one.


To get started, install or update via npm:

npm i bootstrap-icons

Or Composer:

composer require twbs/bootstrap-icons

You can also download the release from GitHub, or download just the SVGs and fonts (without the rest of the repository files).


The Figma file is now published to the Figma Community! It’s the same Bootstrap Icons Figma file you’ve seen from previous releases, just a little more accessible to those using the app.

Bootstrap Icons v1.7.0

@mdo November 01, 2021

Bootstrap Icons v1.7.0 is here with 120 new and updated icons, taking us over 1,500 total icons for the project! It’s the largest update since the initial release, so keep reading to see what’s new.

120 new icons

This update was a lot of fun for me—drawing all these tiny computer parts most of all! There are dozens of new computer-related icons for parts, ports, and peripheral devices. There are also several new brand icons, including Meta, and some other fun icons like a new robot head and a boombox.

New icons in v1.7.0

Looking for more new icons? Head to the issue tracker to check for open requests or submit a new one.


To get started, install or update via npm:

npm i bootstrap-icons

Or Composer:

composer require twbs/bootstrap-icons

You can also download the release from GitHub, or download just the SVGs and fonts (without the rest of the repository files).


The Figma file is now published to the Figma Community! It’s the same Bootstrap Icons Figma file you’ve seen from previous releases, just a little more accessible to those using the app.