How to link/add custom CSS to bootstrap theme in Drupal 8

Question

I am new to Drupal 8 and want to link a custom CSS file in my bootstrap subtheme. There is no way to link the CSS file in the theme.info.yml file. however, I was able to link my custom CSS in theme.info in Drupal 7. Guide me on how to add custom CSS in the Drupal 8 bootstrap subtheme.

Answer 1

Bootstrap is designed for you to add extra CSS to a subtheme, not the main theme.

The Bootstrap documentation says this:

Warning You should never modify any theme or sub-theme that is packaged and released from Drupal.org, such as Drupal Bootstrap. If you do, all changes you have made will be lost once that theme is updated. Instead, you should create a subtheme from one of the provided starterkits (this is considered a best practice). Once you've done that, you can override CSS, templates, and theme processing.

Bootstrap even provides starter kits so you can easily make the theme yourself, plus step-by-step documentation.

Answer 2

Though it's not a good idea to add your own CSS to a base-theme, you need to add it to bootstrap.libraries.yml

Answer 3

Don't do on main theme instead create a sub-theme and change what you like. Here are some links that can help you set up Bootstrap sub-theme

• https://www.webfoobar.com/node/9
• https://drupal-bootstrap.org/api/bootstrap/docs%21Sub-Theming.md/group/sub_theming/8

You can use either SASS or LESS starterkit. Hope this helps you.