Performance
Cumulative Layout Shift (CLS)
A Core Web Vital that measures how much a page's content unexpectedly shifts while it loads. Lower scores mean a calmer, more stable reading experience.
Cumulative Layout Shift quantifies visual stability: the annoying moments when a button moves just as you reach for it, or text jumps down as a late image loads. It is one of the three Core Web Vitals and a confirmed ranking signal.
A good CLS score is 0.1 or below. The common causes are images and embeds without declared dimensions, ad or banner slots that inject themselves after load, and web fonts that reflow text when they swap in.
The fixes are mostly disciplined front-end work: set explicit width and height (or an aspect ratio) on media, reserve space for anything injected later, and load fonts in a way that avoids a jump. Because layout shift is so visible, getting CLS right is one of the quickest ways to make a site feel more trustworthy and polished.