The CSS Working Group has published an updated Working Draft of CSS Cascading and Inheritance Level 5.
This CSS module describes how to collate style rules and assign values by way of cascading and inheritance.
Level 5 adds “layers” to the cascade, along with a syntax for defining and sorting those layers. In the same way that cascade origins provide a balance of power between user and author styles, cascade layers provide a structured way to organize and balance concerns within a single origin – such as element defaults, third-party libraries, themes, components, and overrides.
The changes have been made since the previous Working Draft:
- Reserve the CSS-wide keywords for future use in layer-names.
- Clarify that @layer rules respect global conditional rules, but are always applied to the layer order when declared in non-global conditions such as a container query.
- Clarify that name-defining at-rules follow layer order for collision resolution, similar to specificity resolution.
- Disallow interleaving of @layer with @import or @namespace rules.
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