SEO
CLS (Cumulative Layout Shift)
Quick definition
CLS is a Core Web Vitals metric measuring unexpected layout shifts that occur as a page loads, scored from 0 (perfect) to higher (worse).
CLS target: under 0.1. Shifts happen when images load without reserved dimensions, ads inject above content, or fonts swap and reflow the page.
Why CLS (Cumulative Layout Shift) matters
High CLS frustrates users — they tap one place and another element loads underneath. It's both a UX and ranking concern.
How CLS (Cumulative Layout Shift) works in practice
Fix CLS by always setting width/height on images and iframes, reserving ad slot space, preloading fonts, and avoiding inserting new content above existing content.