Technical Seo
Cumulative Layout Shift (CLS)
A Core Web Vital that measures unexpected visual movement on a page as it loads. It quantifies how much content shifts around without user interaction. Google considers a score under 0.1 as good.
Why Cumulative Layout Shift (CLS) Matters for SEO
Layout shifts are the reason you accidentally click the wrong button when a page jumps around. Beyond annoying users, poor CLS scores hurt your Core Web Vitals assessment and can contribute to higher bounce rates, especially on mobile.
How Cumulative Layout Shift (CLS) Works
The browser calculates a shift score based on the size of the shifting element and how far it moved. Every time an element moves without user input, the score increases. Common causes are images without dimensions, ads injecting above content, and web fonts swapping in with different sizes.
Common Mistakes
- Not setting explicit width and height on images and video embeds
- Injecting dynamic ad slots that push content down after initial load
- Using font-display: swap without matching fallback font metrics
Want to go deeper?
Read the full guide: Core Web Vitals →
Sources & Further Reading: