Site Speed Optimization: From 4.2s to 1.1s Load Time
This sample case study demonstrates our performance audit methodology and systematic approach to improving Core Web Vitals. All metrics shown are example data illustrating typical optimization results.
The challenge
A business website was experiencing slow load times, particularly on mobile devices. Visitors were bouncing at higher rates than industry averages, and Google Search Console was flagging Core Web Vitals issues affecting search performance.
The client needed a comprehensive audit to identify specific bottlenecks and a clear plan for improvements. This case study illustrates our methodology for performance optimization projects.
Initial metrics (sample data)
- Lighthouse Performance Score: 42/100
- Largest Contentful Paint (LCP): 4.2 seconds
- First Input Delay (FID): 180ms
- Cumulative Layout Shift (CLS): 0.28
- Total Page Size: 3.8 MB
Our approach
1. Baseline Measurement & Analysis
We conducted comprehensive testing using Lighthouse, WebPageTest, and Chrome User Experience Report data. Testing covered desktop and mobile, fast and slow connections, multiple geographic locations.
Key findings identified:
- Unoptimized images accounting for 2.4MB of page weight
- Render-blocking CSS and JavaScript delaying initial paint
- No browser caching configured for static assets
- Third-party scripts loading synchronously
- Missing width/height attributes causing layout shifts
2. Optimization Implementation
We addressed issues systematically, prioritizing by potential impact:
Image Optimization
Converted images to WebP format, implemented responsive images with srcset, added lazy loading for below-fold images, and properly sized all images. Reduced image payload from 2.4MB to 580KB without visible quality loss.
Critical CSS & JavaScript
Inlined critical CSS for above-the-fold content, deferred non-critical JavaScript, implemented code splitting, and removed unused code. Eliminated render-blocking resources delaying initial paint.
Caching Strategy
Configured aggressive browser caching for static assets, implemented service worker for offline functionality, and set up CDN with proper cache headers. Repeat visitors now experience near-instant loads.
Layout Stability
Added explicit width/height attributes to all images and embeds, reserved space for dynamic content, and implemented skeleton screens for asynchronous content. Eliminated unexpected layout shifts.
3. Testing & Verification
After implementation, we conducted extensive testing to verify improvements across various scenarios. Monitoring was set up to catch any future regressions. All changes were validated against multiple devices and connection speeds.
Results (sample data)
Post-optimization measurements showed significant improvements across all Core Web Vitals metrics:
Final metrics
Business impact (sample metrics)
- Mobile bounce rate decreased by 34%
- Average session duration increased by 28%
- Contact form submissions increased by 22%
- Pages per session increased from 2.3 to 3.1
Key takeaways
This case study demonstrates our systematic approach to performance optimization. Real projects follow the same methodology: measure baseline, identify specific issues, implement targeted fixes, and verify improvements.
Performance optimization delivers measurable business benefits beyond vanity metrics. Faster sites keep visitors engaged, improve conversion rates, and perform better in search results. The investment in proper optimization typically pays for itself through improved outcomes.
Every site has unique bottlenecks requiring specific solutions. Cookie-cutter optimization approaches miss opportunities. Our audits identify what actually matters for your specific situation.
Need a performance audit?
We'll identify your site's specific bottlenecks and provide a clear optimization plan with realistic expectations.
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