CSS and SCSS Coding Conventions


This document provides guidelines for code formatting to developers contributing to SilverStripe. It applies to all CSS/Sass files in the SilverStripe core modules.

In 2016, SilverStripe started a rewrite of the styles of the CMS interface. This rewrite is work-in-progress so code written prior to this rewrite might not follow these conventions, and is placed in a legacy/ folder structure.

Browser support

Check our requirements documentation.

Tools and libraries

Styles are written in the SCSS language. We use Bootstrap 4 styles where possible.


We follow the AirBnB CSS Conventions and the BEM methodology (block-element-modifier).

Because we use Bootstrap 4 which does not follow BEM naming convention there will be a lot of places where class names voilate BEM. However, please note that they are not a indicator of how to name classes. Use BEM conventions where possible.


We use sass-lint to ensure all new SCSS written complies with the rules below. It will be provided as an npm dev dependency. There are also quite a few [sass-lint IDE integrations] which highlight any linting errors right in your code.

We strongly recommend installing one of these into the editor of your choice, to avoid the frustration of failed pull requests. You can run the checks on console via yarn run lint.

File and Folder Naming

  • All frontend files (CSS, JavaScript, images) should be placed in a client/ folder on the top level of the module
  • Frontend files relating to the framework CMS UI should be placed in admin/client
  • The client/src/components folder should contain only reusable components (e.g. Button, Accordion). Presentation of these components should not rely on the markup context they're embedded in.
  • The client/src/containers folder should contain use-case dependent styles only (e.g. CampaignAdmin). Styles in here should be kept at a minimum.
  • The file name of styles nested within components and containers should inherit their respective folder name for easy reference. For example, a components/FormAction component has styles named FormAction.scss).
  • The client/src/styles folder contains base styles (reset, typography, variables) as well as layout-related styles which arranges components together.

Icons and Graphics

Most graphics used in the CMS are vector based, and stored as generated webfonts in admin/client/src/font, which also contains a HTML reference. The webfonts are generated through the Fontastic service. If you need new icons to be added, please ping us on Github.

Legacy conventions

CSS written prior to SilverStripe 4.0 is not following the conventions outlined above. It is contained in a legacy/ folder structure. If modifying these styles, consider porting them over into the new structure. Otherwise, follow these conventions:

  • Class naming: Use the cms- class prefix for major components in the cms interface, and the ss-ui- prefix for extensions to jQuery UI. Don't use the ui- class prefix, its reserved for jQuery UI built-in styles.
  • Use jQuery UI's built-in styles where possible, e.g. ui-widget for a generic container, or ui-state-highlight to highlight a specific component. See the jQuery UI Theming API for a full list.

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