Core Web Vitals explained, in plain English.

LCP, INP, and CLS. These are the three numbers Google uses to rank your site on page experience. Here is what each one measures, what the targets are, and how to fix yours. INP replaced FID in March 2024.

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Core Web Vitals. LCP, INP, CLS explained

Why Google invented Core Web Vitals.

Before Core Web Vitals, Google measured site speed with a single number, page load time which did not reflect how sites actually feel to visitors. CWV replaced that with three specific metrics that measure real user experience: how fast does the main content appear (LCP), how fast does the page respond to a tap (INP), and does the layout shift around while loading (CLS).

  • LCP. Largest Contentful Paint, target under 2.5s
  • INP. Interaction to Next Paint, target under 200ms (replaced FID)
  • CLS. Cumulative Layout Shift, target under 0.1
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The three metrics, explained.

Largest Contentful Paint

How long until the main content shows. Target under 2.5s. Usually fixed by optimizing hero images and fonts.

  • How long until the main content shows.
  • Target under 2.5s.
  • Usually fixed by optimizing hero images and fonts.

Interaction to Next Paint

How responsive your page is to taps and clicks. Target under 200ms. Usually a JavaScript problem. Replaced FID in March 2024.

  • How responsive your page is to taps and clicks.
  • Target under 200ms.
  • Usually a JavaScript problem.

Cumulative Layout Shift

How much your layout jumps around while loading. Target under 0.1. Usually caused by unoptimized images, ads, or web fonts.

  • How much your layout jumps around while loading.
  • Target under 0.1.
  • Usually caused by unoptimized images, ads, or web fonts.

How to actually fix each one.

Optimize your hero image (compress, serve WebP, correct dimensions), preload critical fonts, remove render-blocking JavaScript.

  • Optimize your hero image (compress, serve WebP, correct dimensions), preload critical fonts, remove
  • Use srcset for responsive images that load appropriate sizes
  • Lazy load below-the-fold images to prioritize LCP element

Reduce JavaScript bundle size, defer non-critical scripts, break up long-running tasks, lazy-load third-party widgets.

  • Reduce JavaScript bundle size, defer non-critical scripts, break up long-running tasks, lazy-load th
  • Move third-party scripts to load after page becomes interactive
  • Consider removing unused plugins and widgets

Set explicit width and height on images and ads, avoid inserting content above existing content, use font-display: swap carefully.

  • Set explicit width and height on images and ads, avoid inserting content above existing content, use
  • Reserve space for dynamic content like ads with min-height CSS
  • Use font-display: swap to prevent layout shift from web fonts

FID measured only the delay to a first click. INP measures all interactions throughout the page lifetime. INP is a better metric. Google made the switch in March 2024.

  • FID measured only the delay to a first click.
  • INP measures all interactions throughout the page lifetime.
  • INP is a better metric.
Find Your Issues

How SchemaReports measures Core Web Vitals.

SchemaReports fetches your live page in a browser context and measures LCP, INP, and CLS the same way Chrome does for real users. Not simulated. Not cached. Real values on the live site. Every slow element is identified by selector. Phase 1 of every audit, free or paid.

  • Live measurement, not simulation
  • Element-level identification
  • Specific fix recommendations
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How SchemaReports measures Core Web Vitals live

See Core Web Vitals in Action

LCP, CLS, and INP — watch how SchemaReports measures the exact metrics Google uses to rank your site.

Measure Your Vitals
Performance
CORE WEB VITALS
LCP ? 6.8 s
0s 2.5s 4s+
FCP ? 4.1 s
0s 1.8s 3s+
CLS ? 0.003
0 0.1 0.25+
TBT ? 380 ms
0ms 200ms 600ms+

Core Web Vitals, common questions

Do Core Web Vitals actually affect rankings?

Yes, they are a confirmed Google ranking signal as part of the page experience update.

  • Same measurement tools Google uses for ranking decisions
  • Both mobile and desktop scores analyzed separately
What is a good score?

Under 2.5s LCP, under 200ms INP, under 0.1 CLS.

  • Good scores give you a ranking advantage in competitive searches
  • Poor scores can push you down even if your content is solid
What happened to FID?

Retired in March 2024 and replaced by INP. INP is a better metric because it measures the entire page lifetime.

  • Scores can change when you update plugins or add new content
  • Regular tracking shows if your improvements actually worked
Why is TBT not a Core Web Vital?

TBT is a lab metric (measured during development). INP is a field metric (measured from real users). Google ranks on field metrics.

  • Most impact in competitive industries where content quality is similar
  • Better performance also means better user experience and conversions
Can I use Lighthouse instead?

Lighthouse runs a lab version of the check. SchemaReports runs the live version. Both are useful, live is more accurate.

  • Field data shows real-world performance across different devices and connections
  • Lab data provides consistent testing for tracking improvements over time

  • Audit your plugins and remove ones you don't actually need
  • Better hosting makes a bigger difference than any optimization plugin

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10,000+ sites have already been audited. See what's holding yours back, 12 phases, 1,000+ data points, AI-powered analysis. Completely free.

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  • 12 phases, 1,000+ data points, results in under 5 minutes
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