Definition
Cumulative Layout Shift (CLS) measures the visual stability of a webpage as it loads, focusing on how often unexpected layout shifts occur. It is one of the three Core Web Vitals metrics used by Google to assess page experience. CLS is calculated during the most active five-second window of layout shifts, excluding shifts that occur within 500 ms of user interactions.
User Cases
In real-world scenarios, CLS can affect user experience by causing elements on a page to move unexpectedly. This can lead to users clicking on the wrong links or buttons, disrupting their navigation. For example, a user might intend to click a product link but ends up clicking an ad due to a layout shift, which can be frustrating and lead to a poor user experience.
Why It Matters for SEO
CLS is crucial for SEO because it directly impacts user experience, which is a significant factor in search engine rankings. A low CLS score indicates a stable page, enhancing user satisfaction and potentially improving page rankings. Google uses CLS as part of its Core Web Vitals to evaluate the quality of user interactions on a site, making it essential for maintaining good SEO performance.
Related Concepts
CLS is closely related to other Core Web Vitals metrics such as Largest Contentful Paint (LCP) and First Input Delay (FID), which together provide a comprehensive measure of page performance. Understanding these metrics can help improve overall site performance and user experience.