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performanceWeb Platform

CSS Containment for Performance

SHOULD

SHOULD: Use CSS `contain: layout paint` on reusable cards/list items to isolate layout/paint scope. Use `content-visibility: auto` with `contain-intrinsic-size` for offscreen content (up to 7x render improvement).

Use CSS contain and content-visibility to isolate layout/paint scope

Bad

Good

Why it matters

CSS containment tells the browser that an element's layout/paint is independent from the rest of the page. content-visibility: auto skips rendering offscreen content entirely, dramatically improving initial render for long lists.

References

Built by Gleb Stroganov, design engineer at Evil Martians.

The rules come from other people's skills and guidelines — Vercel, Rauno Freiberg, @Ibelick, impeccable, Emil Kowalski, Tailwind, RAMS — each one credited on the Sources page. The work here is extraction and wiring: every rule is pulled into one corpus, given a good and a bad example you can operate, a MUST/SHOULD/NEVER rule an agent can paste, and a link back to where it came from.