Real Lighthouse scores, Core Web Vitals, CrUX field data, opportunities and diagnostics — all in one place.
Most tools show you a score. We show you the full picture — lab data, real users, third-party impact, and exactly what to fix.
Understand every metric, what it means, and the fastest way to improve it.
Everything you need to know about web performance auditing and this tool.
Lab data comes from Google Lighthouse running a simulated test on a controlled device with a fixed network speed (Slow 4G for mobile). It is great for debugging and consistent comparisons. Field data (CrUX) comes from real Chrome users visiting your site over the last 28 days and reflects actual conditions like varying devices, network speeds, and geographic locations. Google uses field data — not lab data — as a ranking signal in Search.
Chrome UX Report only includes data for origins with a statistically sufficient number of Chrome users over the past 28 days. Low-traffic or newly launched websites typically do not have enough data to appear. This is normal and does not negatively affect your rankings — Google simply does not have enough data to make a field-data assessment and falls back to lab data for those sites.
Core Web Vitals (LCP, INP, CLS) are confirmed Google ranking signals since 2021. However, they are a tiebreaker signal — meaning high-quality, relevant content still matters most. If two pages have similar content quality, the faster page with better CWV scores will rank higher. Failing CWV thresholds is unlikely to tank a well-established site, but passing them gives a measurable edge in competitive search results.
Lighthouse scores can vary run-to-run by 5–10 points due to network variability, server response time fluctuations, and variability in the cloud machine running the audit. Results are cached for 5 minutes to reduce quota usage. For the most accurate picture, run multiple audits and average the scores. The CrUX field data is far more stable as it aggregates data from thousands of real visits.
Start with the Opportunities tab — items are sorted by estimated time savings. In most cases, the highest-impact fixes are: (1) compress and convert images to WebP/AVIF, (2) eliminate render-blocking JavaScript and CSS, (3) preload the LCP image with <link rel="preload">, (4) enable text compression (Brotli/Gzip), and (5) use a CDN to reduce server response time. These five fixes alone typically account for 60–80% of total potential improvement.
Yes, completely free. The tool uses Google's PageSpeed Insights API which allows 25,000 requests per day at no cost. Results are cached for 5 minutes, so repeated analyses of the same URL use cached data. In the rare event of API quota exhaustion, the tool falls back to a basic HTML analysis that still provides page size, script count, image analysis, and basic SEO checks. No signup, no account, no credit card required.
TBT is the sum of all time periods between First Contentful Paint and Time to Interactive where the main thread was blocked for more than 50ms. Each blocking period contributes (duration - 50ms) to the TBT score. A high TBT means users cannot click buttons, type in inputs, or scroll smoothly during page load. TBT is Lighthouse's lab proxy for INP — reducing TBT almost always improves real-world interactivity.
Run a performance audit after every significant change to your site — new features, theme updates, new marketing scripts, or image uploads. For ongoing monitoring, a weekly automated audit is ideal. Track your scores over time to catch regressions early. It is especially important to audit after adding any third-party scripts (analytics, chat widgets, ad tags) as these frequently cause the biggest performance regressions.
High-impact improvements you can implement today.