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Core Web Vitals

Core Web Vitals are three Google metrics of how a page feels to real visitors: how fast the main content loads (LCP), how quickly the page responds to a tap or click (INP) and how stable the layout stays (CLS).

How it works

Google sets a “good” line for each metric: Largest Contentful Paint (LCP) within 2.5 seconds, Interaction to Next Paint (INP) of 200 milliseconds or less, Cumulative Layout Shift (CLS) of 0.1 or less. Each is read at the 75th percentile of real page loads, separately for mobile and desktop. A page passes when all three are good.

Google’s search ranking uses Core Web Vitals, but Google seeks the most relevant page first. Google Ads reports its own measures instead: a speed score from 1 to 10 for mobile ad clicks and a landing page experience rating for keywords. Site speed for online stores shows which problems cost ad-driven sales.

Ways to calculate

  • Field data: real Chrome users over the previous 28 days. PageSpeed Insights bases its Core Web Vitals assessment on it, as does Search Console’s report (About PageSpeed Insights).
  • Lab data: one simulated load in Lighthouse, which gives the 0–100 performance score. With no real user it cannot measure INP (Web Vitals).

Example

Example store, not client data.

The tableware shop’s product pages on mobile: LCP 3.1 s, INP 180 ms, CLS 0.05. Three in four loads show the main content within 3.1 s. INP and CLS are good, but LCP is above 2.5 s, so the pages fail on mobile. On desktop LCP is 1.9 s, and all three pass.

Not to be confused with

  • Page speed — how fast a page loads, measured in many ways. Core Web Vitals are three fixed metrics with set lines.

Right and wrong readings

  • Wrong: “PageSpeed Insights scores the page 45, so it fails Core Web Vitals.” Right: the score comes from one simulated load. The assessment comes from 28 days of real visits, and the two can disagree.

Benchmarks

Benchmark according to the HTTP Archive Web Almanac 2025 (Chrome UX Report data, millions of websites, July 2025): 48% of websites on mobile and 56% on desktop had good Core Web Vitals. This covers the whole web, not only stores: your niche may differ.

Sources