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Core Web Vitals

Core Web Vitals
Speed Matters for AI

Check LCP, FID, and CLS scores. Slow sites get deprioritized by Google AI Overviews, ChatGPT, and Perplexity.

Google PageSpeed
100% Free
Real Lab Data

What We Measure

LCP — Largest Contentful Paint

How long until the largest element is visible. Target: ≤2.5s

FID — First Input Delay

How long until the page responds to interaction. Target: ≤100ms

CLS — Cumulative Layout Shift

How much the page layout shifts during load. Target: ≤0.1

Frequently Asked Questions

What are Core Web Vitals and why do they matter?
Core Web Vitals are Google's official page experience metrics: LCP, FID, and CLS. They directly impact rankings and how AI search engines like Google AI Overviews decide which sources to cite.
What is a good LCP score?
Good LCP is ≤2.5 seconds. It measures how long the largest visible content element takes to render. Slow LCP means AI may skip your page.
What is a good CLS score?
Good CLS is ≤0.1. It measures visual stability. Pages that shift around frustrate users and get lower AI citation priority.
How can I improve Core Web Vitals?
For LCP: optimize images, use CDN, preload key resources. For FID: minimize JavaScript, defer non-critical scripts. For CLS: set image dimensions, avoid dynamic content injection.

About this tool

Core Web Vitals scores rarely tell you what to fix. They tell you something is slow. Whether that's your hero image, a third-party chat widget, or a CSS animation that nobody asked for is left as an exercise for the reader.

This checker runs against Google's own PageSpeed Insights API — the same source that powers your Search Console reports. You get the lab numbers (Lighthouse), the field data (real users via the Chrome User Experience Report), and a prioritized list of which audits actually move the needle. We don't pretend that "Reduce unused JavaScript" is actionable advice on its own; we point at the actual heavy script and tell you what's loading it.

Worth knowing: a single Lighthouse run is noisy. The same URL can swing 20 points between consecutive runs depending on network and server load. If a score surprises you, run it three or four times before panicking. The field data is steadier — that's what Google actually uses for ranking, and it lags lab numbers by 28 days.

How to check your Core Web Vitals

Run a free Core Web Vitals scan against Google PageSpeed Insights.

  1. 1
    Paste your URL

    Enter your full website URL into the input field at the top of the tool.

  2. 2
    Run the scan

    Click the scan button. The tool fetches your page and runs the analysis in the background.

  3. 3
    Review results

    Review the report. Each finding includes a plain-English explanation and a recommended fix.

  4. 4
    Apply fixes

    Implement the recommended changes on your site, then re-run the scan to confirm the issue is resolved.

Frequently asked questions

What are Core Web Vitals?+
Three metrics Google uses as direct ranking signals: Largest Contentful Paint (LCP, loading), Interaction to Next Paint (INP, responsiveness), and Cumulative Layout Shift (CLS, visual stability).
What scores should I aim for?+
LCP under 2.5 seconds, INP under 200 milliseconds, and CLS under 0.1. Pages above these thresholds qualify for a "good" page experience signal in Google Search.
Where does the data come from?+
The tool uses Google PageSpeed Insights API, which combines lab data (Lighthouse) with real-user field data from the Chrome User Experience Report (CrUX) when available.
Why does the score differ between runs?+
Lab tests vary based on network conditions, server load, and any third-party scripts. Field data (CrUX) is more stable but requires enough real visitor traffic to populate.
Does this also check mobile?+
Yes. Mobile is checked by default because Google uses mobile-first indexing. You can re-run any URL for desktop-specific results.

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