Harry Roberts explains an underused CSS feature that lets the browser skip unnecessary layout and paint work. The article covers each contain value (layout, paint, size, style), the content and strict shorthands, and content-visibility for lazy rendering. It includes an OpenTable example where contain: strict cut layout time from 11 ms to under 2 ms by limiting scope from 4371 nodes to just 73.
csswizardry.com/2026/04/what-is-css-containment-and-how-can-i-use-it