Core Web Vitals Optimization Case Study

Improving Core Web Vitals is one of the best investments you can make in your site’s performance and SEO. Here's a breakdown of how I took a slow-loading site and transformed it into a lightning-fast, Google-approved experience.

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✅ Faster load times
✅ SEO uplift
✅ Better user engagement
✅ Lighthouse scores improved across the board

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🧪 The Starting Point

One of my freelance clients had a beautifully designed marketing site — but performance-wise, it was dragging. On initial tests:

• LCP (Largest Contentful Paint): 4.2s
• CLS (Cumulative Layout Shift): 0.18
• FID (First Input Delay): 97ms
• Performance Score (Lighthouse): 63

Google Search Console had started warning them about poor performance.

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🔧 Optimization Techniques

Here's what I did to turn things around:

✅ Image Optimization

• Used <picture> + srcset for responsive images
• Served WebP where supported
• Compressed hero images with TinyPNG

✅ Font Loading

• Used font-display: swap
• Reduced number of weights/variants
• Self-hosted Google Fonts

✅ Layout Shift Fixes

• Added height placeholders to images and embeds
• Prevented Flash of Unstyled Text (FOUT) by loading fonts early

✅ Code Optimization

• Replaced jQuery animation with CSS transitions
• Minified and tree-shook JS
• Lazy-loaded non-critical components

✅ Hosting & CDN

• Moved to Netlify for faster global delivery
• Enabled Brotli + gzip compression

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📈 Before & After

Metric	Before	After
LCP	4.2s	1.5s
CLS	0.18	0.03
FID	97ms	28ms
Lighthouse Score	63	98

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🛠 Tools Used

• Lighthouse (Chrome DevTools)
• PageSpeed Insights
• GTmetrix
• WebPageTest.org
• Chrome Performance Profiler

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💡 Key Takeaways

• Always audit images first — they're usually the biggest culprit.
• Fonts can have a huge impact on perceived performance.
• Minor layout tweaks (like reserving space) = big CLS wins.
• Don't underestimate hosting + CDN — they can level up any stack.

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💬 CTA

Looking to boost your Core Web Vitals and climb the SEO ranks?
I specialize in performance optimization for modern web apps.

Get in Touch or email me directly

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Thanks for reading 🙌