Cumulative Layout Shift (CLS)
Cumulative Layout Shift (CLS) measures the visual instability caused by unexpected movement of visible page content.
What is Cumulative Layout Shift?
Cumulative Layout Shift (CLS) is a Core Web Vital that measures unexpected movement of visible content. A layout shift happens when an element changes position between rendered frames without the user expecting it.
CLS is unitless. Google recommends a score of 0.1 or less at the 75th percentile of page visits, with scores above 0.25 considered poor.
Why does CLS matter for B2B websites?
Unexpected movement makes pages harder to use. A buyer may start reading a service page, move toward a button or form, and then see the content jump as an image, embed or banner loads. On high-intent landing pages, that creates avoidable friction around conversion actions.
CLS also matters as part of broader technical SEO, but the practical goal is visual stability rather than chasing a score in isolation.
What causes a high CLS score?
Common causes include images or videos without reserved dimensions, late-loading embeds, dynamically injected content, web-font swaps and animations that change layout properties. On a Webflow website, third-party scripts, cookie banners, forms and custom interactions can introduce these shifts after launch.
How do you measure CLS?
Use PageSpeed Insights to compare real-user field data with lab diagnostics. Google Lighthouse can identify layout shifts during a test load, but it may miss shifts that happen later while users scroll or interact.
How do you improve Cumulative Layout Shift?
Reserve space before content loads. Set image dimensions or aspect ratios, give embeds and dynamic components predictable containers, avoid inserting banners above existing content, and prefer transform-based animations over properties that trigger re-layout.
Review recurring components as the website architecture grows, because one unstable CMS component can affect many URLs. Include CLS checks in launch QA and ongoing maintenance of the B2B marketing website.
Key takeaway
CLS measures unexpected visual movement. Aim for 0.1 or less for most users, find the elements causing shifts, and reserve their space before they load.
