Extending Drupal 8’s ‘Classy’ theme is a great way to bootstrap your theme. However, specifying a parent theme in your
theme.info.yml will also include its libraries.
An easy way to remove included libraries from your child theme is to use
libraries-override, like so:
This will stop the
classy.base library from being included in your theme.
You can also override a library, changing which resources gets loaded:
This will replace the
classy.base library with
my_theme.base library, and replace
dialog.css from the
classy/dialog library with your own