PageSpeed Performance Audit (Lighthouse)
Analyze mobile & desktop site speed with real Google PageSpeed Insights data — LCP, CLS, FCP, Speed Index, TBT scores, and screenshots, free.
Analyze Web Performance & Core Web Vitals
Powered by Google PageSpeed Insights API with real Mobile & Desktop Base64 screenshots.
How to Use PageSpeed Performance Audit (Lighthouse)
Enter the URL to be tested and click 'Analyze PageSpeed'. The tool queries the Google PageSpeed Insights API directly, so the data shown is the exact data Google itself uses to evaluate your page.
Compare Mobile vs. Desktop results side by side with Core Web Vitals (LCP, CLS), supporting metrics (FCP, Speed Index, TBT), Field Data vs Lab Data, and rendered device screenshots.
Field Data reflects real Chrome visitor experience (CrUX report); Lab Data reflects a controlled simulated test run. Understanding both gives you an honest assessment of actual user experience.
Review Diagnostics and Passed Audits for specific, fixable causes — image sizing, render-blocking resources, and JS execution time — behind your score.
Why It Matters
- ✓Largest Contentful Paint (LCP) and Cumulative Layout Shift (CLS) are the two Core Web Vitals with direct SEO weight.
- ✓Mobile and desktop performance are scored independently — a page can pass on one and fail on the other.
- ✓Field Data reflects real visitor experience; Lab Data reflects a controlled test, and the two can diverge significantly.
- ✓Diagnostics and 'Passed Audits' point to specific, fixable causes behind a low score.
Key Features
- •Real Google PageSpeed Insights API data, not a simulation
- •Separate Mobile and Desktop views with mockups
- •Field Data vs. Lab Data comparison
- •Live Base64 screenshots of page load stages
- •Full Diagnostics and Passed Audits breakdown
Frequently Asked Questions
Everything you need to know about PageSpeed Performance Audit (Lighthouse)
Why is the mobile score so much lower than the desktop score?
Mobile devices generally have less processing power, and Lighthouse's mobile test simulates a mid-tier device on a throttled connection — so render-heavy or JavaScript-heavy pages usually score lower on mobile even with identical code.
What counts as a 'good' LCP, CLS, and FCP score?
Google's thresholds place LCP under 2.5 seconds, CLS under 0.1, and FCP under 1.8 seconds in the 'Good' range. Anything above these moves into 'Needs Improvement' or 'Poor.'
Why does Field Data sometimes show worse results than Lab Data?
Lab Data is measured under ideal, controlled conditions on a single test run. Field Data aggregates real visitors on real networks and devices — including older phones and slower connections — so it often paints a more honest picture.
Does a perfect Lighthouse score guarantee good rankings?
No. Speed is one of many ranking factors. A fast site with thin content still won't outrank a well-optimized page with strong content — but a slow site puts a ceiling on how well even great content can perform.
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