Web performance directly impacts user satisfaction, engagement, and revenue. This article covers practical techniques for optimizing your web applications.
Why Performance Matters
- 53% of mobile users abandon sites that take longer than 3 seconds to load
- A 1-second delay in page load time can reduce conversions by 7%
- Google uses Core Web Vitals as a ranking signal
Core Web Vitals
Google's three key metrics:
Largest Contentful Paint (LCP)
Measures loading performance. Target: under 2.5 seconds.
- Optimize images (serve WebP/AVIF, use responsive sizes)
- Eliminate render-blocking resources
- Use a CDN
First Input Delay (FID) / Interaction to Next Paint (INP)
Measures interactivity. Target: under 100ms (FID), under 200ms (INP).
- Break up long tasks
- Defer non-critical JavaScript
- Use web workers for heavy computations
Cumulative Layout Shift (CLS)
Measures visual stability. Target: under 0.1.
- Set explicit dimensions on images and embeds
- Reserve space for dynamic content
- Use font-display: swap
Image Optimization
Images account for over 50% of page weight on average. Best practices:
- Use next-gen formats (WebP, AVIF)
- Implement lazy loading
- Serve responsive images with srcset
- Use image CDNs
JavaScript Optimization
- Code-split with dynamic imports
- Tree-shake unused code
- Defer non-critical scripts
- Minimize bundle size
Caching Strategies
- Use service workers for offline support
- Implement aggressive caching for static assets
- Use CDN caching for dynamic content
Monitoring and Testing
- Lighthouse for lab data
- Web Vitals library for field data
- Real User Monitoring (RUM) for production insights
Conclusion
Performance optimization is an ongoing process. Start by measuring your current performance, identify the biggest opportunities, and iterate. Even small improvements can have a significant business impact.