Page Speed Check methodology
The tool runs Google PageSpeed Insights performance analysis for mobile and desktop. Each device result is kept separate, stamped with its Lighthouse version and collection time, and never averaged with another engine.
Lab data and real-user data
Lighthouse metrics are controlled lab estimates from one run. Chrome UX Report values, when available through PageSpeed Insights, summarize real visits. The report labels these sources separately. A missing real-user section means there was not enough eligible traffic; it does not mean the page failed.
Recommendations
The tool selects a bounded set of Lighthouse opportunities and ranks them by estimated time savings, then byte savings. Estimates are directional and are not additive. Audit availability can change between Lighthouse versions, so a missing opportunity is not treated as an error.
Variability
Networks, servers, page content, ads, experiments, and browser scheduling can all change a score. Compare like-for-like device results and confirm important changes with repeated measurements.
Privacy and limits
The submitted public URL is sent to Google PageSpeed Insights. Reports are private by default, cached for a limited time to reduce repeated work, and shareable only after explicit publication. Private and published report pages are excluded from search indexing.
The tool accepts one public HTTP or HTTPS page on a standard port. Private, local, metadata-service, credential-bearing, and non-web targets are rejected. Rate limits and per-page cooldowns protect the service from abuse.