$devvkit resources --research web-performance:-core-web-vitals-and-optimization-strategies
Web Performance: Core Web Vitals and Optimization Strategies
3min[web][performance][frontend]
TL;DR: Core Web Vitals (LCP, CLS, INP) measure real-world user experience. Optimizing them improves SEO and conversion rates directly.
Key findings
- •LCP (Largest Contentful Paint) measures perceived load speed. Target: under 2.5 seconds. Optimization: preload critical resources, minimize render-blocking CSS/JS, use responsive images.
- •CLS (Cumulative Layout Shift) measures visual stability. Target: under 0.1. Optimization: set explicit dimensions on images/embeds, reserve space for dynamic content, avoid inserting content above existing content.
- •INP (Interaction to Next Paint) measures responsiveness. Target: under 200ms. Optimization: avoid long tasks, use passive event listeners, split heavy computation with requestAnimationFrame.
- •CDN caching and static pre-rendering reduce LCP by 40-60 percent. The fastest request is the one that never reaches your server.
Why this matters for developers
Google uses Core Web Vitals as a ranking signal. Every 100ms improvement in LCP correlates with 1-2 percent improvement in conversion rates. Performance is UX.