CLS (Cumulative Layout Shift)

The Core Web Vital for visual stability: how much visible content jumps around as the page loads — the annoyance of tapping a button that just moved because an ad loaded. Target: under 0.1. Fixed by setting explicit width/height on images, videos, ads and embeds so the browser reserves their space.

First used in: 2.4 · Technical SEO II — rendering, speed & mobile