Google's Core Web Vitals are specific metrics that measure real-world user experience on web pages. Since becoming a ranking factor in 2021, they directly influence search visibility.

The Three Core Web Vitals

Largest Contentful Paint (LCP)

Measures loading performance. Target: under 2.5 seconds.

Interaction to Next Paint (INP)

Measures responsiveness -- the time between user interaction and visual update. Replaced FID in 2024. Target: under 200 milliseconds.

Cumulative Layout Shift (CLS)

Measures visual stability -- unexpected content shifts during loading. Target: under 0.1.

Why Core Web Vitals Matter

Google uses them as a ranking signal. They correlate with user satisfaction, lower bounce rates, and better conversion rates. Many websites still fail assessments, creating competitive opportunity.

How to Measure Core Web Vitals

Use Google PageSpeed Insights for lab and field data, Google Search Console for site-wide performance, Chrome DevTools for debugging, and the Web Vitals JavaScript Library for real-user measurement.

Improving LCP

Optimize images with modern formats (WebP, AVIF) and lazy loading
Minimize render-blocking CSS and JavaScript
Use a CDN for geographic proximity
Reduce server response time
Preload critical resources
Remove heavy third-party scripts

Improving INP

Break up long JavaScript tasks into smaller chunks
Minimize JavaScript execution time
Reduce DOM size
Use web workers for heavy computation

Improving CLS

Set explicit dimensions on images and videos
Reserve space for ads and embeds
Avoid inserting content above existing content
Load web fonts properly with font-display: swap

The Impact of Analytics Scripts

Google Analytics' script adds approximately 45KB and executes JavaScript that can delay LCP and impact INP. Lightweight analytics alternatives (some under 1KB) have negligible impact. Auditing third-party scripts is one of the highest-impact improvements you can make.