Cascade layers

Supported Per Spec Updated: Dec 17, 2025

Allows for controlling the specificity and order of rule sets across stylesheets.

Baseline:
Widely
Functional:
Supported
Usage:
Cross-Context

Cascade layers can be defined and used independently within both light DOM and shadow DOM stylesheets with full support for shadow DOM selectors like ::slotted().

Shadow-defined cascade layers cannot interact with or impact global layer order, even with identical layer names, as each shadow root is isolated.

Web Platform Test
Chrome 147
Edge 146
Firefox 149
Safari 26.4
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WPT sources: layer-slotted-rule