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.

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.

Our AI analyzes your Core Web Vitals alongside 50+ other performance metrics to identify exactly what's slowing your site down.

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Largest Contentful Paint

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

  • Identifies which element is your LCP (often hero images or headings)
  • Measures load time on mobile and desktop separately
  • Recommends specific fixes like image compression or lazy loading
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SchemaReports performance and technical SEO audit showing Core Web Vitals results

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.

  • Detects blocking JavaScript that delays interactivity
  • Measures response time for first user interaction
  • Suggests script optimization or deferral strategies
Test Interactivity
SchemaReports trust signals, psychology and ADA compliance audit results

Cumulative Layout Shift

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

  • Identifies elements causing layout shifts (ads, images, fonts)
  • Calculates total shift score across page load
  • Recommends size attributes for images and reserved space for dynamic content
Check Layout Stability

How to actually fix each one.

Based on thousands of audits, these are the problems killing most websites' performance scores.

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

  • Convert to WebP or AVIF format for better compression
  • 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.

  • Defer non-critical scripts with async or defer attributes
  • 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.

  • Add explicit width and height attributes to all images
  • 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.

  • Enable caching to serve repeated requests from memory
  • Use a CDN to serve static assets from edge locations
  • Optimize database queries and consider better hosting
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
Test Mobile Performance
How SchemaReports measures Core Web Vitals live

Core Web Vitals, common questions

Common questions about Google's performance metrics and how we measure them.

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
Can I pass Core Web Vitals with a WordPress site?

Yes, but it requires attention to plugins, themes, and hosting. WordPress sites often struggle with Core Web Vitals because of plugin bloat and cheap hosting. Use caching plugins, optimize images, and choose a fast theme.

  • 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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Find out where your Core Web Vitals actually stand.

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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