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D8 Configuration - Development - CSS Injector Navigation

1. Navigate to CSS Injector

Go to Admin Menu > Configuration > Development > Asset Injector > CSS Injector.

D8 Configuration - Development - Click Add CSS Injector Button

2. Add CSS Injector

Click the Add CSS Injector button to create a new injector.

D8 Configuration - Development - Add CSS

3. Configure CSS Injector

Label text field = enter a name for your CSS Injector.

Code text area = add your CSS classes here. Add as many classes as you need. Make sure you annotate things well.

Advanced Options

Media select field = all is default, leave this as is.

Preprocess CSS checkbox = checked by default. This aggregates CSS into a single file which results in a performance boost. Keep it checked.

Conditions Section

There are many different conditions that are available. Additional conditions may also be added as more contributed modules are enabled.

For now, we'll just set the theme condition as it's most relevant.

Click the Current Theme vertical tab.

Theme select list = Bootstrap.

Click the Save button.

Note: if you would like to continue editing your CSS after saving, click the Save and Continue Editing button.

Flush the cache.

D8 Configuration - Development - Style Changes Applied

4. Styles Applied

Go to a page in your site where your style changes will display. If your CSS is valid, you should see your changes.