Google's Core Web Vitals are now a ranking factor. A slow site is an invisible site.

The Three Pillars

1. Largest Contentful Paint (LCP)

What: Loading performance. How fast does the main content load?

Goal: < 2.5 seconds.

Fixes:

  • Optimize images (WebP/AVIF).
  • Preload critical fonts.
  • Use a CDN.

2. Interaction to Next Paint (INP)

What: Interactivity. How fast does it respond to a click?

Goal: < 200 ms.

Fixes:

  • Break up long tasks in JS.
  • Defer non-essential JS.

3. Cumulative Layout Shift (CLS)

What: Visual Stability. Do elements jump around?

Goal: < 0.1.

Fixes:

  • Set explicit width/height on images.
  • Reserve space for ads.

Tools for Measurement

  • Lighthouse: Lab data (simulation).
  • PageSpeed Insights: Lab + Field data (real users).
  • Chrome UX Report: Historical data.