Why Performance Matters
Website performance directly impacts user experience, conversion rates, and search rankings. Studies show that a 1-second delay can result in 7% reduced conversions, 11% fewer page views, and 16% decreased customer satisfaction.
Core Web Vitals
Google's Core Web Vitals measure real-world user experience:
- Largest Contentful Paint (LCP): Measures loading performance (should occur within 2.5 seconds)
- First Input Delay (FID): Measures interactivity (should be less than 100ms)
- Cumulative Layout Shift (CLS): Measures visual stability (should be less than 0.1)
Optimizing Asset Delivery
Efficient asset delivery is crucial for fast loading:
- Minify CSS, JavaScript, and HTML
- Compress images (WebP format typically offers best compression)
- Implement lazy loading for images and iframes
- Use CDN for global content distribution
- Enable HTTP/2 or HTTP/3 for multiplexing
- Set proper cache headers
JavaScript Optimization
JavaScript often causes performance bottlenecks:
- Defer non-critical JavaScript
- Code-split large bundles
- Remove unused code (tree shaking)
- Use web workers for CPU-intensive tasks
- Avoid long tasks that block the main thread
CSS Optimization
Efficient CSS improves rendering performance:
- Critical CSS should be inlined in the head
- Remove unused CSS with tools like PurgeCSS
- Avoid expensive properties like box-shadow in animations
- Use contain property to limit rendering scope
- Prefer transforms and opacity for animations
Font Optimization
Web fonts can significantly impact performance:
- Use font-display: swap to avoid invisible text
- Subset fonts to include only needed characters
- Preload critical fonts
- Consider system fonts for maximum performance
- Variable fonts can reduce file sizes
Server Optimization
Server configuration affects performance:
- Enable compression (Brotli preferred over Gzip)
- Implement proper caching headers
- Use a reverse proxy like Nginx
- Consider edge computing for dynamic content
- Database optimization for dynamic sites
Monitoring and Maintenance
Continuous monitoring ensures sustained performance:
- Set up Real User Monitoring (RUM)
- Use synthetic monitoring tools
- Create performance budgets
- Regularly audit with Lighthouse
- Establish a performance culture in your team