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Folder structure

Breeze styles located in <theme_dir>/web/css/ folder and organized using the 7-1 pattern.

Path Description
abstracts/ Less variables and mixins placed here. Everything that doesn’t produce css output.
base/ Reset styles, CSS properties, typography, forms, CSS helper classes.
components/ Reusable components styles (Tabs, Modal, Spinner, etc).
layout/ Unique blocks styles (Header, Layered Navigation, Listing, Search, etc).
pages/ Page-specific styles (Cart, Customer, etc). These are potential candidates for dedicated CSS bundle.
vendor/ A place for the third-party modules styles. We’ve put Luma mixins here to provide easier integration with styles written for Luma theme.
_extend.less Empty file for developer needs. Base entry point for child theme.
_custom.less Empty file for end-client needs. Place it in your custom theme and add any kind of customizations. Added after _extend.less.
default.less Default CSS bundle that is used across all pages.
checkout.less CSS bundle that is used at checkout page only.


We use CSS bundles to group styles based on their usage per page. Each bundle has critical and deferred part. Currently, there are two bundles used only:

  • default.less — commonly used styles goes here. This bundle added on all pages.
  • checkout.less — styles for checkout page. Added on checkout page only.

Each bundle provides additional file for deferred styles that doesn’t affect layout shifts.

  • deferred-default.less
  • deferred-checkout.less

Styles are splitted into critical and deferred parts based on LESS guard added around the styles. See the next section for more information.

Critical and deferred styles

When writing styles for Breeze theme, you must put your styles inside @critical CSS guard. By doing that you tell Breeze where to put your styles. When your styles can cause layout shift you should use & when (@critical) guard. Otherwise — use & when not (@critical) guard.

Warning! Do not forget to enclose your styles into CSS guard, otherwise your styles will be duplicated in both output files.

Let’s see an example to undestand better. Here is how layout/_breadcrumbs.less is coded:

& when (@critical) {
    .breadcrumbs {
        min-height: @9;
        ul {

& when not (@critical) {
    .breadcrumbs a:hover {
        text-decoration: underline;

The code above will be compiled by Magento into two separate files. Critical styles will be added to default.css, and non-critical will be added to deferred-default.css file.

Don’t forget to enable Use CSS critical path config option to get maximum benefit of the critical CSS:

bin/magento config:set dev/css/use_css_critical_path 1