Cumulative Layout Shift (CLS)
01 Definition
Cumulative Layout Shift (CLS) meaning: CLS measures how much page content unexpectedly moves while it loads.
Cumulative Layout Shift is a Core Web Vitals metric from Google that scores how much visible content shifts position unexpectedly during loading. It is a unitless score, not a time. Google considers 0.1 or less at the 75th percentile a good result.
Why it matters
How Cumulative Layout Shift (CLS) fits the work
CLS is Google's visual stability signal in Core Web Vitals, so a low score means content stays put instead of jumping as the page loads.
In context
A news page cut its CLS from 0.28 to 0.05 after the team reserved space for banner ads that had been pushing articles down as they loaded.
Practical note
Set width and height on images and reserve space for ads and embeds to prevent shifts. CLS is a score, so lower is better and zero is ideal.