Cumulative Layout Shift (CLS)

Cumulative Layout Shift (CLS) is one of Google's Core Web Vitals that measures visual stability. It quantifies unexpected layout shifts of visible page elements. A high CLS score indicates that page elements are moving around unexpectedly, which is frustrating for users and a sign of poor frontend performance. CLS is calculated by tracking the sum of all individual layout shift scores that occur without user input during the entire lifespan of the page.