Core Web Vitals

Largest Contentful PaintLCPLargest Contentful Paint: the time until the largest image or text block in the first screen is rendered. Google rates 2.5 seconds or less as good.In the glossary (LCP), the first of the three Core Web VitalsCore Web VitalsGoogle's three measures of page experience: LCP for loading, INP for responsiveness and CLS for visual stability. Each is judged at the 75th percentile of real visits.In the glossary, measures the time until the largest image or text block in the visible area has been drawn. Google rates up to 2.5 seconds as good and more than 4 seconds as poor. Interaction to Next PaintINPInteraction to Next Paint: how quickly a page visibly responds to clicks, taps and key presses during a visit. Google rates 200 milliseconds or less as good.In the glossary (INP) observes every click, tap and key press during a visit and reports roughly the slowest response; good is up to 200 milliseconds, poor more than 500. INP replaced the older First Input Delay in 2024. Cumulative Layout ShiftCLSCumulative Layout Shift: how much visible content moves unexpectedly while a page loads and is used. Google rates a score of 0.1 or less as good.In the glossary (CLS) adds up how far visible content moves unexpectedly; good is up to 0.1, poor more than 0.25.

A page passes when 75 percent of visits meet all three thresholds, evaluated separately for mobile and desktop. The values come from real Chrome users and are published in the Chrome UX Report, PageSpeed Insights and Google Search Console. Lab tools such as Lighthouse simulate a single page load instead. They help to find causes, but they cannot measure INP without a real visitor and often differ from field data.

Google describes the Core Web Vitals as part of the page experience that its ranking systems reward. It also states that relevance comes first and that a highly relevant page can rank well despite a poor page experience. Good values therefore help most where many pages answer the same question equally well.

Visitors respond to the same qualities directly. In an A/B test by Vodafone, a landing page with a 31 percent better LCP generated 8 percent more sales. Most sites still fall short: in July 2025 only 48 percent of websites passed all three metrics on mobile and 56 percent on desktop. On mobile, LCP was the weakest, good on only 62 percent of sites (Web Almanac 2025).

Each metric has typical causes. LCP suffers from large or late images, slow server responses and stylesheets or scripts that block rendering. INP suffers from long JavaScript tasks that keep the browser busy when the visitor taps. CLS typically comes from images without declared dimensions, late web fonts, and ads or embeds that push content down; 62 percent of mobile pages contain at least one image without dimensions.

Field data needs enough traffic. A small or new site may have no values in the Chrome UX Report, and then only lab measurements remain until visitors provide data.