Google's Tools Are the Authority
For Core Web Vitals, PageSpeed Insights is the source of truth. Everything else is supplementary. Understand the difference between lab data and field data before optimizing anything.
PageSpeed Insights
Shows both lab data (Lighthouse) and field data (CrUX). Field data is what Google uses for rankings. Lab data is useful for debugging. Always check field data first—if it passes, you're fine. Don't optimize lab scores if your field data is already good.
Google's Tools
Start here. These are authoritative for what Google measures.
PageSpeed Insights
USE ITThe authoritative Core Web Vitals source. Shows field data (real user metrics from Chrome) and lab data (Lighthouse). Field data is what matters for rankings. The "origin summary" shows your whole domain's performance.
Lighthouse
USE ITBuilt into Chrome DevTools. Lab testing with detailed diagnostics. Treemap shows exactly what's slowing your page. Run locally for consistent results without network variability. Essential for debugging performance issues.
Chrome UX Report (CrUX)
USE ITReal user data from Chrome users who opted in. This is what Google uses for rankings. Access via BigQuery for detailed analysis or via Search Console for your sites. The ultimate source of truth for Core Web Vitals.
Third-Party Testing Tools
Useful for detailed analysis and comparisons.
WebPageTest
USE ITThe most detailed waterfall analysis. Test from multiple locations with real browsers. Filmstrip view shows visual loading progress. Video comparison for before/after. Free and incredibly deep. Essential for serious performance work.
GTmetrix
SITUATIONALClean UI, good waterfall visualization. Easier to understand than WebPageTest. Uses Lighthouse under the hood. Good for quick checks and client-friendly reports. Not authoritative for CWV—use PageSpeed Insights for that.
DebugBear
SITUATIONALContinuous performance monitoring. Track Core Web Vitals over time. Alerts when performance degrades. Good for ongoing monitoring after you've optimized. The CrUX History tool is free and useful.
Yellow Lab Tools
SITUATIONALOpen-source performance analysis. Detailed reports on JavaScript, CSS, and HTML issues. Good for identifying specific optimization opportunities. Useful complement to Lighthouse's recommendations.
Pingdom
SKIP ITLegacy speed test tool. The metrics don't align with Core Web Vitals. Pingdom is useful for uptime monitoring, but use PageSpeed Insights or GTmetrix for speed testing.
Lab Data vs Field Data
Lab data is synthetic testing—Lighthouse running in controlled conditions. Useful for debugging but doesn't reflect real user experience.
Field data is real user metrics from Chrome users (CrUX). This is what Google uses for rankings. If your field data passes, you're good.
Don't obsess over lab scores. A page can have a "bad" Lighthouse score and still pass Core Web Vitals in the field. The field data is what matters.