Poor Cumulative Layout Shift (CLS)

What This Means

The page's Cumulative Layout Shift — the sum of layout shift events during the page load — is in the "Poor" range (above 0.25). CLS measures how much visible content unexpectedly moves during loading. Google considers CLS below 0.1 "Good" and above 0.25 "Poor".

Why It Matters for SEO

Layout shift is directly visible to users: text jumps down as an image loads; a button shifts position just as a user is about to click it. High CLS is one of the most frustrating user experiences on the web. Google uses CLS as a Core Web Vitals signal — high CLS pages may be demoted in rankings relative to stable pages.

What the Platform Checks

Measures CLS score via performance data. Fires when CLS is in the "Poor" band (>0.25).

How to Fix It

• Add size attributes to all images: The number one cause of CLS is images loading without reserved space. Add width and height attributes to all <img> elements.
• Reserve space for ads and embeds: Ad slots that expand when filled should have reserved minimum dimensions in CSS.
• Avoid inserting content above existing content: Banners, cookie notices, and popups that push content down cause high CLS. Use fixed-position overlays that don't displace content.
• Preload custom fonts: Fonts that cause text reflow when they load (FOUT) contribute to CLS. Use font-display: swap with preloaded fonts to minimize reflow.
• Reserve space for late-loading content: Any element that loads asynchronously (ads, social embeds, dynamic content) should have its space reserved in CSS before loading.