• A CSS mechanism to indicate that an element’s subtree is independent of the rest of the respective page. This isolation of a subtree allows a browser to optimize rendering and improve performance. ↑ w3.org/TR/css-contain-3

1. Related terms: Critical CSS · Shadow DOM · Bidirectional isolation
2. Previous term: Containing block
3. Next term: Content
4. Random term: Primitive (webglossary.info/random 🎲)