Answer · SEO Services

What Are Core Web Vitals?

2 min read353 words

WDCT Senior Strategist Web Design Company Tampa · Editorial

Updated May 16, 2026

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The short answer

Core Web Vitals are three Google-defined metrics that measure user experience on a page: Largest Contentful Paint (LCP, when the biggest content renders), Interaction to Next Paint (INP, how fast the page responds to clicks), and Cumulative Layout Shift (CLS, how much the page jumps during load). Targets: LCP under 2.5s, INP under 200ms, CLS under 0.1.

№ 01The longer answer

LCP measures when the largest above-the-fold element renders. On 90% of B2B sites, this is the hero image or hero headline. Target: under 2.5 seconds good, under 1.8 seconds great. Failing LCP usually means a too-large hero image, slow hosting, or render-blocking JavaScript.

INP replaced FID (First Input Delay) in March 2024. It measures the slowest interaction response across the entire page session, not just the first one. Target: under 200ms. Failing INP usually means too much JavaScript blocking the main thread — the page-builder problem.

CLS measures unexpected layout movement during page load. The classic offender: images without explicit width/height attributes that cause the page to jump as images load. Target: under 0.1. Failing CLS usually means missing image dimensions, late-loading fonts, or banner injection.

Google uses CWV as a ranking signal (a tiebreaker, not a primary driver) and reports field data — real user data from Chrome — in GSC’s Core Web Vitals report. Synthetic tests (Lighthouse, PageSpeed Insights synthetic) are diagnostic but don’t drive ranking; the field data does.

№ 02How do I check my Core Web Vitals?

GSC’s Core Web Vitals report is the source of truth (uses real-user field data). PageSpeed Insights shows both field data and synthetic. Lighthouse is synthetic-only. For ranking decisions, trust the field data.

№ 03Are Core Web Vitals a major ranking factor?

Moderate. CWV is a tiebreaker between equally-ranked pages. If your competitor passes CWV and you don’t, they win the tiebreaker. If you both pass, content and links decide. CWV won’t move you from page 5 to page 1; it can move you from position 6 to position 3.

№ 04Do CWV thresholds vary by device?

Yes. Google measures CWV separately for mobile and desktop. Mobile thresholds are the same but harder to hit because of network variability. Most CWV failures show up on mobile first.

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