Core Web Vitals
Google's three main metrics:
- LCP (Largest Contentful Paint) < 2.5 sec
- FID (First Input Delay) < 100 ms
- CLS (Cumulative Layout Shift) < 0.1
Images
The main source of performance issues:
- WebP/AVIF formats
- Lazy loading
- Proper sizes (srcset)
- Blur placeholder
Code Optimization
- Code splitting
- Tree shaking
- Minification
- Removing unused CSS
Fonts
Fonts often block rendering:
- font-display: swap
- Preloading critical fonts
- Character subsetting