How to Decrease Cumulative Layout Shift (CLS)

Improve Your Website’s Visual Stability and User Experience

What Is Cumulative Layout Shift (CLS)?

Cumulative Layout Shift (CLS) measures how much elements on your webpage move unexpectedly while it’s loading.
It’s one of Google’s Core Web Vitals, along with Largest Contentful Paint (LCP) and First Input Delay (FID).

A low CLS score means your website feels stable and smooth. A high CLS score means users see elements jumping around — a frustrating experience that can hurt conversions and search rankings.

Google recommends keeping CLS below 0.1 for optimal performance.

Why CLS Matters

• User Experience: Shifting buttons and text can make visitors click the wrong element — leading to frustration.

• SEO Ranking: CLS directly affects your Core Web Vitals, which are part of Google’s ranking signals.

• Professionalism: A stable, polished site feels more trustworthy and well-built.

Common Causes of Poor CLS

1. Images and videos without dimensions

2. Ads or embeds loading dynamically

3. Fonts swapping or flashing on load

4. Late-loading banners, popups, or cookie notices

5. Dynamic content injected above existing elements

Step-by-Step: How to Decrease CLS

1. Always Set Width and Height for Images and Videos

When browsers know the exact dimensions, they reserve the correct space before loading the media.
This prevents content from shifting downward once the image loads.

✅ Example:

Modern CSS can also help:

2. Reserve Space for Ads and Embedded Content

Ads or embedded YouTube videos can cause major shifts when they appear later.

✅ Fix:

• Use a fixed container height for ads or embeds.

• If ad size varies, use the largest possible height to prevent sudden jumps.

3. Load Fonts Properly

When custom web fonts load late, text may “flash” or shift (known as FOUT or FOIT).

✅ Fix:

• Use font-display: swap; in your CSS.

• Preload key fonts for faster rendering.

4. Avoid Injecting Content Above the Fold

Never insert banners, popups, or forms at the top after the main content loads — it pushes everything down.

✅ Fix:

• Insert new elements below existing content or overlay them instead.

• Use lazy loading wisely: load below-the-fold content after initial render.

5. Preload Important Elements

Preloading large images, fonts, and critical CSS ensures your layout is ready before anything moves.

✅ Fix:

6. Use CSS Instead of JavaScript for Layouts

When possible, use CSS Grid or Flexbox layouts instead of dynamic JS scripts.
JS-driven elements often shift positions after DOM rendering.

✅ Tip:
Keep animations and layout transitions subtle — and avoid layout-affecting motion during load.

7. Measure and Monitor CLS

You can’t fix what you don’t track. Use free tools like:

• 🧠 Google PageSpeed Insights

• 📊 Lighthouse

• 🧾 [Chrome DevTools → Performance → Experience Metrics]

• 🌐 Web Vitals Chrome Extension

Check your “Cumulative Layout Shift” score and note which elements move, then fix those specific cases.

Pro Tips to Improve CLS Without Breaking Design

• Use CSS aspect-ratio to keep your layout flexible.

• Preload above-the-fold assets first.

• Use lazy loading for below-the-fold images only.

• Test your site on mobile; CLS issues often appear more there.

• Reduce third-party scripts and unnecessary widgets.

Ideal CLS Targets

Final Thoughts

Improving Cumulative Layout Shift isn’t just about pleasing Google; it’s about creating a stable, trustworthy, and enjoyable user experience.

By setting image dimensions, reserving space for ads, preloading assets, and controlling font behavior, you can dramatically improve your CLS score without sacrificing design quality.

A stable website looks professional, performs better in search, and builds trust with every scroll.