—Glossary
Core Web Vitals
Core Web Vitals are three Google metrics for a web page's real-world user experience: how fast it loads, how quickly it responds, and how stable its layout stays.
Core Web Vitals are part of Google's Web Vitals initiative. Google Search Central describes them as "a set of metrics that measure real-world user experience". Each one stands for a moment visitors notice: a page that sits blank, a button that doesn't respond, a link that jumps as you tap it.
The three metrics
| Metric | What it measures | "Good" threshold |
|---|---|---|
| Largest Contentful Paint (LCP) | Loading: when the largest image, text block or video in view has rendered | 2.5 seconds or less |
| Interaction to Next Paint (INP) | Responsiveness: the delay between a click, tap or key press and the page's visual response, across the whole visit | 200 milliseconds or less |
| Cumulative Layout Shift (CLS) | Visual stability: how much content moves unexpectedly while the page is open | 0.1 or less |
Google's web.dev guidance is to measure each metric at the 75th percentile of page loads, separately for mobile and desktop. In practice, at least three in four visits should meet the threshold. INP replaced First Input Delay (FID) as a Core Web Vital in 2024.
Why they matter
For search, Google recommends that site owners achieve good Core Web Vitals and says doing so "aligns with what our core ranking systems seek to reward". Treat them as a floor, not a ranking trick: speed helps a page that already answers the search, and it doesn't replace the answer.
Measure them on real visits. Lab tools are useful for finding causes, but the thresholds are judged on what your visitors experience, on their phones and connections.
How it relates to Worcia
Worcia builds websites to Core Web Vitals targets and reports LCP and INP from real mobile visits against Google's "good" thresholds. SEO & GEO, Worcia's search and AI-answer optimization service, fixes speed problems on existing sites. If you're planning a rebuild, read how to redesign a website without losing your search rankings.
Sources
- Web Vitals. web.dev (Google), October 31, 2024.
- Understanding Core Web Vitals and Google search results. Google Search Central, December 10, 2025.
- Interaction to Next Paint is officially a Core Web Vital. web.dev (Google), March 12, 2024.