Frontend & Design

Core Web Vitals Optimization

Measure and optimize Core Web Vitals (LCP, INP, CLS) to improve user experience and search engine rankings.

Claude Code Cursor Copilot Windsurf Gemini CLI

Overview

Core Web Vitals are Google's key metrics for user experience: Largest Contentful Paint (LCP), Interaction to Next Paint (INP), and Cumulative Layout Shift (CLS). AI agents can analyze your code for performance bottlenecks and implement optimizations that improve these metrics directly.

Your AI agent can implement lazy loading for images and components, optimize critical rendering paths, add `fetchpriority="high"` to LCP elements, implement proper image dimensions to prevent CLS, defer non-critical JavaScript, and use `requestIdleCallback` for non-urgent work. These changes can dramatically improve your real-user metrics.

The `web-vitals` JavaScript library lets you measure these metrics in production. AI agents can set up Real User Monitoring (RUM) to track vitals, identify pages with poor scores, and systematically fix issues like render-blocking resources, unoptimized images, and layout shifts caused by dynamic content.

Who Is This For?

Frontend developers optimizing LCP by prioritizing critical resources
Teams fixing CLS issues caused by dynamic content and ads
Performance engineers implementing INP optimizations for interactive pages
SEO teams improving search rankings through better Core Web Vitals

Installation

Setup for Claude Code

npm install web-vitals
Claude Code can analyze and optimize your code for CWV

Configuration

// Measure Core Web Vitals
import { onLCP, onINP, onCLS } from "web-vitals";

onLCP(console.log);
onINP(console.log);
onCLS(console.log);

// Send to analytics
onLCP((metric) => {
  fetch("/api/vitals", {
    method: "POST",
    body: JSON.stringify({ name: metric.name, value: metric.value }),
  });
});