Core Web Vitals Tuner

Improve LCP, INP, and CLS systematically.

LCP Optimization (<2.5s)

Prioritized Fixes:

Optimize images (Biggest impact)

<!-- Before --> <img src="hero.jpg" />

<!-- After --> <img src="hero.jpg" srcset="hero-400.webp 400w, hero-800.webp 800w, hero-1200.webp 1200w" sizes="(max-width: 600px) 400px, (max-width: 1200px) 800px, 1200px" loading="eager" fetchpriority="high" />

Preload LCP resource

<link rel="preload" as="image" href="/hero.webp" fetchpriority="high" />

Inline critical CSS

<style> /* Above-the-fold styles */ .hero { display: flex; height: 100vh; } </style>

Use CDN

• Serve images from CloudFront/Cloudflare

• Enable HTTP/2 or HTTP/3

INP Optimization (<200ms)

Fixes:

Debounce expensive interactions

import { debounce } from "lodash";

const handleSearch = debounce((query) => { fetchResults(query); }, 300);

Use Web Workers for heavy tasks

const worker = new Worker("processor.js"); worker.postMessage(largeData); worker.onmessage = (e) => console.log(e.data);

Code splitting

const HeavyComponent = lazy(() => import("./HeavyComponent"));

CLS Optimization (<0.1)

Fixes:

Reserve space for images/ads

<img src="banner.jpg" width="1200" height="600" />

Use CSS aspect-ratio

.video-container { aspect-ratio: 16 / 9; }

Avoid injecting content above existing

.notification { position: fixed; top: 0; }

Verification

Lighthouse CI

npm run lighthouse -- --url=https://example.com

Web Vitals in production

import { getCLS, getFID, getLCP } from 'web-vitals';

getCLS(console.log); getFID(console.log); getLCP(console.log);

Output Checklist

• LCP optimized (<2.5s)

• INP optimized (<200ms)

• CLS optimized (<0.1)

• Monitoring in place

• Performance regression tests ENDFILE