What the PageSpeed Check measures

The tool runs Google's PageSpeed Insights Lighthouse audit against any public URL and returns four category scores on a 0–100 scale, plus the Core Web Vitals field metrics that Google uses for ranking.

Performance (0–100): how quickly the page loads and becomes interactive. Green (≥90) is fast; red (<50) is slow enough to lose users and rankings.
Accessibility (0–100): structural checks for screen readers, color contrast, focus order, ARIA usage, and form labeling.
Best Practices (0–100): security (HTTPS, mixed content), browser errors, deprecated APIs, and modern web platform usage.
SEO (0–100): technical on-page signals — meta description, crawlability, link text, viewport, structured data.

Core Web Vitals

Three field metrics that Google uses as a ranking signal and reports inside Search Console.

LCP (Largest Contentful Paint): time for the largest visible element to render. Target: ≤2.5s.
INP (Interaction to Next Paint): responsiveness to taps and clicks. Target: ≤200ms. Replaced First Input Delay in March 2024.
CLS (Cumulative Layout Shift): visual stability. Target: ≤0.1.

Why page speed matters

Slow pages cost rankings and conversions. Google's Core Web Vitals are a confirmed ranking signal, and the commercial impact is measurable: Amazon's 2006 experiments showed every additional 100ms of latency reduced sales by 1%, and Google's 2017 mobile research found that bounce probability increases 32% when page load goes from 1s to 3s. Checking speed isn't optional for any site that relies on organic search.

Who this tool is for

SEO specialists auditing new client sites or validating fixes.
Developers checking performance after a deploy.
Founders sanity-checking how their site compares to a competitor.
Agencies generating quick wins for monthly reporting.

Frequently asked questions

Is the PageSpeed Check really free?

Yes. No signup, no credit card, no rate limit at casual use levels. The tool wraps Google's PageSpeed Insights API, which is itself free.

Are mobile and desktop scores different?

Yes, usually dramatically. Mobile is the default in our tool and the one Google uses for ranking. Desktop scores tend to run 15–25 points higher because the simulated network and CPU are stronger. Always optimise for mobile first.

Why did I get a different score than last time?

Lighthouse uses a simulated network throttle but there's still variance between runs — typically ±5 points on Performance. For stable measurement, run the check 3 times and average. For trending over weeks, the paid MeasureBoard dashboard tracks scores automatically.

How do I improve a low score?

The tool surfaces the top six opportunities from the Lighthouse audit with estimated time savings. Common wins: compress images (convert to WebP/AVIF), defer unused JavaScript, add width and height attributes on images to prevent CLS, and add loading="lazy" on below-fold images.

Does a 100 score guarantee top rankings?

No. Page speed is one ranking factor among many. A 100 score with thin content will lose to an 80-scoring page with stronger topical authority and better backlinks. But a slow page is a handicap you don't need to carry.

Can I track scores over time?

Free tools run one-off checks. MeasureBoard's dashboard runs scheduled Lighthouse audits and charts the four scores plus Core Web Vitals over weeks and months, so you can see whether changes are moving the needle. Sign up free to enable scheduled tracking.