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Add Bootstrap 4 to your Ruby on Rails 6 application

The right way

· Ruby on Rails,Bootstrap,Web App Development,Ruby on Rails 6

Use yarn to add Bootstrap and its dependencies - jquery and popper.js

Run the following command from your application directory (if you don't have yarn, install it):

yarn add bootstrap@4.3.1 jquery popper.js

You can check that the libraries have been installed properly by checking the package.json file (listed under the Gemfile.lock file in your file directory)

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Now for JavaScript

Make the config/webpack/environment.js file look like below:

Make the config/webpack/environment.js file look like below (you are adding the lines which are highlighted in green below):

const { environment } = require('@rails/webpacker')

const webpack = require("webpack")

environment.plugins.append("Provide", new webpack.ProvidePlugin({

$: 'jquery',

jQuery: 'jquery',

Popper: ['popper.js', 'default']


module.exports = environment

This is so your application's javascript understands jquery and popper.js syntax.

Now you have to import bootstrap and it's goodies to your application.js, go to app/javascript/packs/application.js and add the following line to the bottom:

import "bootstrap"

That's it for javascript, now onto CSS

Now onto CSS

Go to app/assets/stylesheets/application.css and add the following line above the require_tree and require_self lines:

*= require bootstrap

So it looks like below:

*= require bootstrap

*= require_tree .

*= require_self

Now to add custom styles to the app styling, create a new file within this folder (app/assets/stylesheets folder) and call it custom.css.scss (app/assets/stylesheets/custom.css.scss).

Here import the bootstrap library first so you are able to modify styles for not just your new classes but existing bootstrap classes as well:

@import 'bootstrap/dist/css/bootstrap';

And that's it! you should be good to go with bootstrap 4 in your Rails 6 application. To test it out, you can add some bootstrap 4 classes (like navbar) to your application layout file and try changing it from this custom.css.scss file. Example test code below:


.navbar {

background-color: #FDF6EA !important;



.navbar-brand {

font-size: 3rem;



h1 {

color: red;


Good luck and enjoy!

- Mashrur