Glossary

What are Core Web Vitals?

By Youssef Hodaigui, Mindflow Marketing · Last reviewed November 1, 2026

Core Web Vitals are three metrics from Google that measure how a page performs for real visitors: loading (Largest Contentful Paint, LCP), responsiveness (Interaction to Next Paint, INP) and visual stability (Cumulative Layout Shift, CLS). Google's web.dev sets the good thresholds at LCP within 2.5 seconds, INP of 200 milliseconds or less, and CLS of 0.1 or less.

They're judged on real visits, not one test. web.dev says to measure at "the 75th percentile of page loads, segmented across mobile and desktop devices," so a page meets a threshold when at least three in four visits do. Google says achieving good Core Web Vitals, along with other page experience aspects, "aligns with what our core ranking systems seek to reward," but relevance still comes first, as our guide to whether site speed affects AI recommendations explains.

What does each metric measure?

Each one tracks a different frustration. LCP is how long the main image or text takes to appear. INP is how quickly the page responds when someone taps, clicks or types. CLS is how much the layout jumps while it loads. Here are web.dev's thresholds, read November 1, 2026, and where each shows up on a contractor's site:

Metric	What it measures	Good	Poor	Where it shows up
LCP	Render time of the largest image, text block or video in view	2.5 seconds or less	Over 4.0 seconds	A large hero photo of a crew or truck
INP	Delay after clicks, taps and key presses	200 milliseconds or less	Over 500 milliseconds	Tapping the menu, a quote form or the call button
CLS	Unexpected layout shifts	0.1 or less	Over 0.25	A banner or review widget pushing the form down as it loads

Between the two thresholds sits a middle band that Google's report labels Need improvement. Our technical SEO checklist puts these checks in order with the rest of a site review, and our web design page explains how we approach website builds.

Why did INP replace First Input Delay?

Because FID only looked at the first tap or click. web.dev says FID "only measured the input delay of the first interaction on a page," while INP observes "all interactions on a page" until the browser paints the next frame. INP became a Core Web Vital on March 12, 2024, replacing FID.

For a contractor, the difference is the tap after the page has loaded: opening the menu, picking a service in a quote form, pressing the call button. A page could pass FID and still feel slow on those. Chrome gave developers until September 9, 2024 to switch from FID to INP, so a report that still grades your site on FID is out of date. web.dev now calls INP "the successor metric to First Input Delay (FID)."

How does Search Console report Core Web Vitals?

By group, not page by page. Google's Core Web Vitals report sorts similar pages into URL groups and rates each group Poor, Need improvement or Good, separately for mobile and desktop. Google says a group's status "is its most poorly performing metric," so one poor CLS score marks the whole group poor even when INP is good.

Two details catch owners out. Only indexed pages appear, and Google says the data "is assigned to the actual URL, not the canonical URL," with URL parameters kept, so an address carrying an ad tracking code can show up separately. Our canonical tag entry explains those duplicate addresses. Low-traffic sites may see few groups or none; the site speed guide linked above covers what to check instead.

Related terms: Canonical tag · robots.txt · Conversion rate · All glossary terms

Where to go next: How much does a website cost for a service business? covers what to budget if speed problems point to a rebuild.

Sources

All read November 1, 2026.

web.dev, Web Vitals (last updated October 31, 2024)
web.dev, Largest Contentful Paint (LCP) (last updated September 4, 2025)
web.dev, Interaction to Next Paint (INP) (last updated September 2, 2025)
web.dev, Cumulative Layout Shift (CLS) (last updated April 12, 2023)
Google Search Central, Understanding Core Web Vitals and Google search results (last updated December 10, 2025)
web.dev, Interaction to Next Paint is officially a Core Web Vital (March 12, 2024)
Search Console Help, Core Web Vitals report

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