PageSpeed & Core Web Vitals Checker

Core Web Vitals are Google’s standardized metrics for real-world page experience: Largest Contentful Paint (LCP) measures loading speed, Interaction to Next Paint (INP) measures responsiveness to user input, and Cumulative Layout Shift (CLS) measures visual stability. Google publishes "good," "needs improvement," and "poor" thresholds for each, and this tool checks your page against those same thresholds.

Field data (from the Chrome User Experience Report, or CrUX) comes from real Chrome users who actually visited the page over the past 28 days — it reflects real devices and connections, but only exists for URLs with enough Chrome traffic. Lab data comes from a single simulated Lighthouse run against the URL, which is available for any page but doesn’t capture real-world variability. This tool prefers field data when Google has enough of it, and falls back to lab data (or omits the metric) otherwise.

Unlike LCP and CLS, INP has no lab-data equivalent in PageSpeed Insights — it can only be measured from real user interactions, so it is only reported when Google’s Chrome User Experience Report has collected enough field data for that exact URL. Lower-traffic pages, and pages checked immediately after being published, often won’t have INP data yet.

Google has confirmed Core Web Vitals are part of its page experience ranking signals, though content relevance and quality generally matter more. Poor Core Web Vitals are more likely to hurt user experience and conversion directly — slow, jumpy, or unresponsive pages lose visitors regardless of where they rank. Treat strong Core Web Vitals as a baseline for a good page experience, not a rankings shortcut on their own.

This tool can run without one using Google’s keyless PageSpeed Insights quota, but that quota is very low and shared across every site using it without a key, so requests can get rate-limited during busy periods. A free Google API key (with the PageSpeed Insights API enabled) gives this tool its own much higher quota for consistent results.