Glossary · SEO & AI searchTOFU
Core Web Vitals
The short answer
Core Web Vitals are three metrics Google uses to measure real-world page experience: how fast the main content loads, how quickly the page responds to interaction, and how stable the layout is while loading.
The three metrics
- LCP — Largest Contentful Paint. Good: 2.5 seconds or less.
- INP — Interaction to Next Paint. Good: 200 milliseconds or less. INP replaced First Input Delay in 2024.
- CLS — Cumulative Layout Shift. Good: 0.1 or less.
A page passes when at least 75% of real visits meet the "good" threshold for each metric.
Field data vs lab data
Lab tools like Lighthouse simulate a load on one device. Field data — from the Chrome UX Report — reflects real users. Google uses field data, and for Indian audiences that usually means mid-range Android phones on variable mobile networks.
Core Web Vitals thresholds
Source: web.dev. See website speed optimisation.
Core Web Vitals in practice
A product page with a large hero image loads slowly on mobile (high LCP). Compressing the image and preloading it improves LCP, and conversion rates often rise alongside.
Thresholds for "good"
- LCP: 2.5 seconds or less
- INP: 200 milliseconds or less
- CLS: 0.1 or less
Core Web Vitals in India
Many Indian users browse on mid-range Android phones and variable mobile networks, so pages that pass on a fast office connection can still fail in the field. Test with real-user data in Search Console.
Common mistakes
- Testing only on desktop
- Heavy third-party scripts
- Unoptimised hero images
Frequently asked questions
Do Core Web Vitals affect rankings?
They're part of page experience signals. Their larger effect is on conversion — slow, jumpy pages lose users.
Where can I check mine?
PageSpeed Insights and the Core Web Vitals report in Search Console.
What replaced FID?
Interaction to Next Paint (INP) replaced First Input Delay as a Core Web Vital in March 2024.
Do Core Web Vitals matter for AI search?
Indirectly — they reflect page experience, and fast, accessible pages are easier for users and crawlers alike.
Where can we check Core Web Vitals?
In Google Search Console, PageSpeed Insights and the Chrome UX Report.
What's the difference between lab and field data?
Lab data comes from simulated tests; field data comes from real users.
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