# 9.3. Working with Bootstrap¶

This topic describes the Bootstrap framework, and how it should be used to build user interfaces within edX applications. Note that Bootstrap adoption started after the Ginkgo release, and so this document applies to the edX master branch and to the forthcoming Hawthorn release.

If you are interested in the rationale for edX choosing Bootstrap, you can read about the decision in OEP-16: Adopting Bootstrap.

## 9.3.1. Getting Started¶

Bootstrap is an open source front end component library that is used by many of the world’s most popular applications. It allows for rapid assembly of front end components using a responsive grid system, a robust component library and easy to configure theming capabilities to ensure that new components are rendered consistently. EdX is using Bootstrap 4 which is a reimplemented version using Sass and that is currently in beta release.

All edX applications should use the edx-bootstrap package that can be installed via npm. This package provides two themes (a default Open edX theme, as well as an edX branded version), and eventually will provide custom Open edX styles for common patterns.

## 9.3.2. Developing Custom Designs¶

Bootstrap provides a large number of components and layouts out-of-the-box, but there will always be a need to implement custom designs. There are a number of considerations to take into account when implementing your designs using Sass.

The most important rule is to avoid hard-coding values such as colors and fonts. Using hard-coded values means that Bootstrap themes will not be able to affect your styles, and so your new elements will look out of place. Whenever possible you should instead use the functions and variables provided by Bootstrap to access theme colors or fonts. See Bootstrap customization options for more details.

For example, here is an example of a hard-coded style:

.my-element {
font-family: "Open Sans";
color: #0000ff;
}

The recommended alternative is as follows:

.my-element {
font-family: $font-family-sans-serif; color: theme-color("primary"); } If you do find the need for a custom color or font that isn’t provided by the edX Bootstrap library, consider first whether it makes sense to contribute it back so that other applications can use this value too. If you decide to add a custom value, define it as a variable that can be overridden by a theme by using the !default flag. This allows themes to provide a different value for this variable if they choose. See the Sass documentation for default flag for more details. For example:$my-custom-color: #0000ff !default;

.my-element {
font-family: $font-family-sans-serif; color:$my-custom-color;
}