CLS Found Causing Ranking Drops on 40% of Audited Client Sites

A technical audit by SEO and development firm Semark Global found that Cumulative Layout Shift (CLS) was silently hurting search rankings on roughly 40% of client websites reviewed. Unlike more commonly flagged issues such as large images or unminified JavaScript, CLS problems were traced to ads, embedded fonts, and lazy-loaded images lacking reserved dimensions. Sites often appeared healthy on other Core Web Vitals metrics like LCP and FID, making CLS harder to identify as the root cause. Common fixes include setting explicit width and height on images, using font-display: swap with matched fallback fonts, and pre-reserving space for late-loading elements. The team noted that PageSpeed Insights' headline score can obscure CLS as a culprit, prompting them to make CLS checks a standard part of every audit.