P0Issue #71
Cumulative Layout Shift (CLS)
❓ What does it mean?
❓ What is CLS?
Cumulative Layout Shift (CLS) is a Core Web Vital metric that measures visual stability of a webpage.
It quantifies how much visible elements unexpectedly move while the page is loading.
Good CLS: ≤ 0.1
Needs improvement: 0.1 – 0.25
Poor CLS: > 0.25
🚨 Why is it important for SEO?
🚨 Why CLS Matters for SEO
Google Ranking Factor → CLS is part of Core Web Vitals, directly impacting rankings.
User Experience → Unexpected shifts frustrate users (e.g., wrong button clicked).
Conversions → Shifting CTAs (e.g., “Buy Now”) hurt trust and reduce sales.
Accessibility → Visually unstable pages feel broken, discouraging engagement.
✅ How to Fix It
❌ Example of Poor CLS
<!-- Image without fixed dimensions -->
<img src="product.jpg" alt="Product Image">
<p>Click below to buy!</p>
<button>Buy Now</button>
The image loads late and pushes down the text and button.
A user might click in the wrong place because the layout shifts.
CLS score will be high (bad).
❌ Bad Example
✅ Example of Optimized CLS
<!-- Image with fixed width & height -->
<img src="product.jpg" alt="Product Image" width="600" height="400">
<p>Click below to buy!</p>
<button>Buy Now</button>
Browser reserves space for the image before it loads.
Page layout remains stable.
CLS score will be low (good).
✅ Good Example
🛠 How to Improve CLS
Always set width & height (or aspect-ratio) for images & videos.
Avoid inserting ads, banners, iframes without reserved space.
Use font-display: swap for web fonts to avoid text jumps.
Preload important fonts & images.
Animate with transform/opacity instead of properties that trigger reflow.
⚡ Result
📈 SEO & UX Benefits
Improves Core Web Vitals score → boosts ranking.
Provides stable browsing experience, lowering bounce rate.
Increases user trust & conversions since CTAs don’t move unexpectedly.