PageSpeed & Core Web Vitals Checker

Run a real Google PageSpeed Insights audit on any URL. See Performance, Accessibility, Best Practices, SEO scores - plus LCP, INP, and CLS. No signup, instant results.

What it checks

A full Lighthouse audit, decoded.

One run, four category scores, every Core Web Vital, and a prioritized fix list.

Performance score

The Lighthouse Performance score (0-100) - a weighted blend of Core Web Vitals and other lab metrics that summarizes how fast the page feels.

Core Web Vitals

Largest Contentful Paint, Interaction to Next Paint, and Cumulative Layout Shift - the three Google search ranking signals you actually need to watch.

Lab metrics

First Contentful Paint, Speed Index, Total Blocking Time, Time to Interactive - the diagnostic signals that pinpoint where time is being spent.

Accessibility, Best Practices, SEO

The other three Lighthouse categories. Catches missing alt text, contrast issues, mixed content, deprecated APIs, robots problems, and more.

Opportunities

Ranked, actionable wins with estimated millisecond and kilobyte savings - unused JavaScript, oversized images, render-blocking resources, and more.

Diagnostics

Deeper signals that need attention but don't have a tidy 'save X ms' number - DOM size, main-thread work, cache policy, image dimensions.

How it works

One URL in, full audit out.

No browser extension, no command line - just paste and read.

Paste a URL

Drop the full URL including https://. Pick a strategy - Mobile (recommended, matches what Google uses for ranking) or Desktop.

Run the audit

We call the official Google PageSpeed Insights API, which runs a real Lighthouse audit on Google's infrastructure. Takes 15-30 seconds.

Read the report

You'll see all four category scores, decoded Core Web Vitals with Good / Needs work / Poor ratings, and a prioritized list of opportunities to fix.

Why PageSpeed matters

Speed is a feature, a ranking signal, and a revenue line.

Core Web Vitals are how Google decides who's fast enough to rank - and how your users decide whether to stay.

User experience

A page that takes four seconds to render loses roughly half its users before they ever see your content. LCP and INP measure exactly that pain - the wait, and the lag - in numbers you can move.

SEO ranking

Google has confirmed Core Web Vitals as a ranking signal since 2021. Pages that fall into the Poor bucket on LCP, INP, or CLS rank below otherwise-equivalent pages that hit Good - same content, lower position.

Conversion

Every 100ms of latency costs measurable conversion - studies from Amazon, Shopify, and Walmart all land in the same range. Performance work has one of the best ROIs in the entire marketing stack.

Reference

Web Vitals thresholds, decoded.

The numbers Google uses to bucket your page as Good, Needs work, or Poor.

LCP - Largest Contentful Paint

How quickly the largest visible element renders. Good ≤ 2.5s, Needs work ≤ 4.0s, Poor > 4.0s. Usually a hero image, headline, or above-the-fold video.

INP - Interaction to Next Paint

How responsive the page feels to clicks, taps, and key presses. Good ≤ 200ms, Needs work ≤ 500ms, Poor > 500ms. Replaced FID in March 2024.

CLS - Cumulative Layout Shift

How much the page jumps around as it loads. Good ≤ 0.1, Needs work ≤ 0.25, Poor > 0.25. Caused by images without dimensions, late-loading ads, or web fonts swapping.

FCP - First Contentful Paint

When the first text or image appears. Good ≤ 1.8s. A fast FCP with a slow LCP usually means a slow hero image or late-loading font.

TBT - Total Blocking Time

Sum of long-task durations between FCP and TTI. The lab proxy for INP. Good ≤ 200ms. High TBT means heavy JavaScript blocking the main thread.

TTFB - Time to First Byte

How long the server takes to start responding. Good ≤ 800ms. High TTFB caps every other metric - no amount of front-end work fixes a slow origin.

FAQ

Frequently asked questions.

Quick answers about the audit and how to read the numbers.

Is this the same as Google's PageSpeed Insights?

Yes - we call the official Google PageSpeed Insights API, which runs Lighthouse on Google's own infrastructure. The scores match what you'd get on pagespeed.web.dev for the same URL.

Why does my score change every time I run it?

Lighthouse is a lab test, and lab tests have variance. Network conditions, CPU contention, third-party scripts, and even time of day move the number. Run the test three or four times and look at the median, not a single run.

Should I optimize for Mobile or Desktop?

Mobile, almost always. Google uses mobile-first indexing, so the mobile score is what affects search ranking. Desktop scores are usually 20-30 points higher and less important.

What's the difference between lab and field data?

Lab data is one synthetic run from a Lighthouse environment - reproducible but artificial. Field data is from real users via the Chrome User Experience Report. Google ranks on field data. This tool returns lab data; you'll see field data on pagespeed.web.dev for popular URLs.

How often should I check PageSpeed?

On every deploy, and any time you add a third-party script, marketing tag, or large image. For continuous coverage, SiteTrak runs PageSpeed automatically every few hours and alerts the moment your Core Web Vitals regress.

Is this tool really free?

Yes - no signup, no email harvesting. We rate-limit per-IP to stay within Google's quota, but otherwise it's open. The paid product is the monitoring side: scheduled audits and regression alerts.

Keep going

Other free tools you'll like.

Run one once, or set up SiteTrak and never run them again.