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Run a real Lighthouse performance test on any URL. Get your LCP, CLS, and INP scores with Google's good/needs improvement/poor labels, plus specific opportunities to improve each metric. Takes about 30 seconds.
⚡ Try the free Core Web Vitals Checker →Core Web Vitals are a set of standardized performance metrics that Google uses to measure real-world user experience on web pages. They are part of Google's Page Experience ranking signals and directly influence search rankings. The three Core Web Vitals are: Largest Contentful Paint (LCP), which measures loading speed; Cumulative Layout Shift (CLS), which measures visual stability; and Interaction to Next Paint (INP), which measures interactivity.
Google began using Core Web Vitals as ranking factors in 2021, and INP replaced First Input Delay (FID) as an official metric in March 2024. Pages with "Good" scores on all three metrics get a Page Experience boost in search rankings. Pages in the "Poor" range may see ranking penalties or be excluded from Top Stories carousels. A Core Web Vitals checker runs your page through Google's Lighthouse engine and returns these scores alongside actionable recommendations.
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Largest Contentful Paint measures how long the main content element takes to load. Slow LCP is almost always caused by render-blocking resources, unoptimized images, or slow server response. Google considers LCP ≤ 2.5s "Good", 2.5–4s "Needs Improvement", and > 4s "Poor".
Cumulative Layout Shift measures how much page content moves around unexpectedly during loading — like an ad loading and pushing text down. CLS above 0.25 is considered "Poor". Even modest CLS causes accidental clicks, frustration, and abandonment. Fixing CLS typically requires setting explicit width/height on images, ads, and embeds.
Interaction to Next Paint replaced FID in 2024. Unlike FID (which only measured the first interaction), INP measures the worst interaction delay across the entire page visit. Pages with heavy JavaScript, third-party scripts, or large DOM sizes score poorly on INP. Google considers INP ≤ 200ms "Good".
Chrome User Experience Report (CrUX) data shows real-world performance from actual Chrome users visiting your site. Lab scores (like Lighthouse) are useful for debugging, but ranking decisions are based on field data. The CWV checker shows both, so you can compare your lab score against real-user experience.
Paste any URL and choose between Mobile or Desktop test. Mobile is the default since Google uses mobile-first indexing, but desktop scores are useful for diagnosing desktop-specific issues.
The tool calls the Google PageSpeed Insights API v5, which runs a full Lighthouse test on the live page. This takes 20–40 seconds — don't close the tab.
The overall performance score (0–100) summarizes page speed. More importantly, check each CWV metric's label — Good, Needs Improvement, or Poor — for LCP, CLS, and INP specifically.
Each identified opportunity includes an estimated saving (in seconds or score points). Prioritize by impact: image compression and CDN improvements typically offer the largest LCP gains, while fixing layout shifts usually requires CSS/HTML changes.
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Yes. Core Web Vitals are a confirmed Google ranking signal as part of the Page Experience update. However, they're a tiebreaker signal — highly relevant content will still outrank slightly faster but less relevant pages. For competitive keywords where content quality is similar, CWV scores can make the difference. Google also uses CWV field data to determine eligibility for Top Stories (mobile news carousel) placements.
Lighthouse runs in a controlled lab environment (simulated mobile hardware, throttled connection). Real-user data comes from Chrome users visiting your actual site with their real devices and connections. Caching, CDN performance, geographic distribution, and device diversity all affect real-user scores. Lighthouse is great for finding issues; real-user (CrUX) data is what Google actually uses for rankings.
The most common LCP fixes are: (1) serve images in WebP or AVIF format, (2) add explicit width/height to the LCP image element, (3) use rel="preload" for the LCP image, (4) upgrade to a faster hosting provider or add a CDN, (5) remove render-blocking scripts in the <head>. The checker's opportunities list will show which of these apply to your specific page.
Common invisible CLS sources include: (1) web fonts swapping after initial render (fix with font-display: optional or preloading fonts), (2) dynamically injected banners, cookie notices, or chat widgets that push content down, (3) iframes or embeds without fixed dimensions, (4) images without explicit width/height attributes in CSS or HTML. Use Chrome DevTools' Performance panel with the Layout Shift Regions layer to visualize exactly which elements are shifting.
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