CSS Cascade Layers (@layer) Explained Simply
Cascade layers give you explicit control over the order in which styles are applied, regardless of selector specificity or source order. Before cascade layers, the order of your CSS file imports and <link> tags determined which styles won when specificity was equal. Third-party library styles loading after yours could override your carefully built design system. Cascade layers solve this by letting you define explicit priority levels for different categories of styles. They are the most significant change to the CSS cascade since specificity itself, and they eliminate an entire class of specificity battles. The Core Problem Imagine you import a component library like Bootstrap after your own styles. Bootstrap uses high-specificity selectors like .btn.btn-primary that beat your single-class .button rule. Your only options were adding !important , increasing your specificity to match, or reordering the imports. All three are fragile. Cascade layers flip this around. You declare priority levels up front, and styles in higher-priority layers always win regardless of specificity. Bootstrap can load after your styles and have more specific selectors. it does not matter, because your layer outranks its layer. How Layers Compare to the Old Cascade Scenario Without…