Cascade layers are a powerful new CSS feature, but browser support requires careful consideration. All major desktop browsers added support between February and April 2022, but older Safari, IE11, and some mobile browsers may not support them. When unsupported, layered styles are ignored entirely. The @supports at-rule for testing @layer support exists in the spec but has no browser implementation yet. The recommended approach for using cascade layers today is the PostCSS cascade layers polyfill (@csstools/postcss-cascade-layers), which can be installed via npm and integrated into a PostCSS pipeline.
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