What Are Core Web Vitals? (Complete 2026 Guide)
Core Web Vitals are a set of three real-user performance metrics defined by Google that measure the most critical aspects of user experience: loading speed (Largest Contentful Paint / LCP), interactivity (Interaction to Next Paint / INP), and visual stability (Cumulative Layout Shift / CLS). They are part of Google's Page Experience ranking signal and are measured from real Chrome user data in the Chrome User Experience Report (CrUX).
What Core Web Vitals Measures
Core Web Vitals answer three fundamental questions about a page: Does the main content load quickly? Does the page respond quickly to interactions? Does content stay stable while loading? The metrics are measured at the 75th percentile of all page loads (p75) — meaning 75% of your users must experience the "good" threshold for your URL to be considered "good" in Google Search Console.
What is a Good Core Web Vitals Score?
What Causes Poor Core Web Vitals Scores?
- ✗Poor LCP: slow server response, unoptimized hero images, render-blocking resources
- ✗Poor INP: JavaScript-heavy pages with long tasks, expensive event handlers, large React component trees
- ✗Poor CLS: images without dimensions, dynamically injected banners, web font reflow
How to Fix Core Web Vitals
- ✓Fix LCP: preload the LCP image, convert to WebP, improve TTFB, use SSR
- ✓Fix INP: reduce TBT by code-splitting JavaScript, deferring third-party scripts, memoizing React components
- ✓Fix CLS: set explicit width/height on all images and iframes, reserve space for dynamic content
- ✓Check all three in Google Search Console under "Core Web Vitals" to see real-user data per URL
Check Your Core Web Vitals Score
Run a free audit at speedexporter.com to see your Core Web Vitals scores alongside both lab data and real-user CrUX field data, with a prioritized list of the specific fixes that will move each metric into the "good" range.
Run a free Lighthouse audit →Frequently Asked Questions
Do Core Web Vitals affect SEO?
Yes. Core Web Vitals are a confirmed Google ranking factor as part of the Page Experience signal. Pages that pass all three Core Web Vitals get a small ranking boost over pages that do not. In highly competitive SERPs, Core Web Vitals can be a tiebreaker.
What happened to FID (First Input Delay)?
First Input Delay (FID) was a Core Web Vital until March 2024, when Google replaced it with Interaction to Next Paint (INP). INP is a more comprehensive measure of interactivity because it considers all interactions during a session, not just the first one.
How do I check my Core Web Vitals?
Google Search Console shows real-user Core Web Vitals data per URL group. PageSpeed Exporter shows both lab estimates and real-user CrUX data in a single report. Chrome DevTools and the web-vitals JavaScript library can show live Core Web Vitals during development.
Are Core Web Vitals measured in the lab or on real users?
Core Web Vitals for SEO purposes are measured from real Chrome users via the Chrome User Experience Report (CrUX). Lighthouse (which PageSpeed Exporter uses) provides lab-based estimates that closely correlate with field data but are not identical. PageSpeed Exporter includes both lab scores and CrUX field data in its export.
What is the difference between Core Web Vitals and Lighthouse score?
Core Web Vitals are three specific metrics measured from real users (CrUX). The Lighthouse Performance score is a weighted composite of 5 lab metrics measured in a controlled simulation. Improving Lighthouse score typically improves Core Web Vitals, but they are different measurements.