How I Improved Core Web Vitals & Increased Website Speed for Better SEO Performance

ByMahesh Dahal

Overview :

This case study shows how I improved a website’s Core Web Vitals and overall performance through technical SEO optimization. The goal was to enhance user experience, reduce load time, and meet Google’s performance standards.

Core Web Vitals comparison before and after technical SEO optimization (mobile and desktop)

The Problem :

Core Web Vitals mobile performance before optimization showing poor page speed score

The website had several performance issues affecting both SEO and user experience:

  • Slow page load speed
  • Poor Core Web Vitals scores
  • High Largest Contentful Paint (LCP)
  • Layout shifts affecting user experience (CLS issues)
  • Unoptimized images and heavy scripts

These issues were negatively impacting search rankings and user engagement.

Audit & Analysis :

I conducted a technical SEO audit using:

  • Google PageSpeed Insights in Google Search Console.

Key issues identified:

  • Large image sizes
  • Render-blocking CSS & JavaScript
  • No proper caching
  • Unoptimized fonts
  • Network dependency tree
  • LCP request discovery
Core web vitals showing metrics issues in PageSpeed Insights
Core web vitals showing Insights issues in PageSpeed Insights

What I Did (Technical SEO Fixes)

1. Image Optimization

  • Compressed images
  • Converted to WebP format
  • Implemented lazy loading

2. Improve Core Web Vitals

LCP (Largest Contentful Paint)

  • Optimized hero images
  • Reduced server response time

CLS (Cumulative Layout Shift)

  • Fixed layout shifting elements
  • Set proper width/height for images

INP / Interaction Optimization

  • Reduced JavaScript execution time

3. Speed Optimization

  • Minified CSS, JS, HTML
  • Removed unused CSS
  • Deferred non-critical JavaScript

4. Caching & Performance

  • Enabled browser caching
  • Reduced server requests

5. Technical Improvements

  • Reduced DOM size
  • Optimized fonts loading
  • Preloaded critical resources

Results

After implementing technical SEO improvements:

  • Page load speed significantly improved
  • Core Web Vitals moved into “Good” range
  • LCP reduced (faster loading time)
  • CLS issues resolved (stable layout)
  • Better user experience and engagement

Before vs After

Before:

  • Slow loading pages
  • Poor Core Web Vitals
  • High bounce rate
Google Search Console Showing Core Web Vitals Before results

After:

  • Fast-loading pages
  • Optimized performance
  • Improved SEO signals

JavaScript Optimization & Cross-Device Fix

During the optimization process, I encountered a device-specific issue between Android and iOS browsers. When applying delayed JavaScript execution in LiteSpeed Cache, the mobile navigation menu failed to function properly on iOS devices, while it worked correctly on Android. To resolve this, I adjusted the JavaScript settings by switching from delay to defer for critical scripts. This ensured smooth navigation functionality across all devices while still maintaining strong Core Web Vitals performance.

Key Learnings

  • Technical SEO plays a major role in rankings
  • Core Web Vitals directly impact user experience
  • Small optimizations can create big performance gains

Conclusion

Improving Core Web Vitals helped enhance both SEO performance and user experience. Technical optimization is essential for any website aiming to rank higher and retain users.

Want to improve your website speed and SEO performance?
👉 Contact me for a technical SEO audit.