Core Web Vitals Explained: Why Google Cares About Your Site Speed

Google uses three metrics — collectively called Core Web Vitals — to measure how users experience your website. Since 2021, these directly affect your search rankings.

LCP — Largest Contentful Paint

What it measures: How long it takes for the biggest visible element (usually a hero image or heading) to load.

Good score: Under 2.5 seconds

How to improve: Compress images, use next-gen formats (WebP), remove render-blocking CSS/JS, use a CDN

FID — First Input Delay

What it measures: How long it takes for the page to respond when a user first clicks, taps, or types.

Good score: Under 100 milliseconds

How to improve: Reduce JavaScript execution time, break up long tasks, use a web worker for heavy processing

CLS — Cumulative Layout Shift

What it measures: How much the page layout moves around as it loads. Those annoying jumps when an ad or image loads late? That's layout shift.

Good score: Under 0.1

How to improve: Set explicit width/height on images and videos, avoid inserting content above existing content, use font-display: swap for web fonts

How to Check Your Scores

Use Google PageSpeed Insights (pagespeed.web.dev) — it's free and shows your Core Web Vitals alongside actionable recommendations.

Why It Matters

Google confirmed that Core Web Vitals are a ranking signal. Two sites with identical content — the faster one ranks higher. If your site is slow, you're losing traffic to competitors who've optimised theirs.