Glossary Terms

real-user monitoring

Real user monitoring, or RUM, measures performance from the browsers of your actual visitors as they use a live site, rather than from a lab test like Lighthouse that simulates one controlled device. It collects timings straight from the browser, recording things like Largest Contentful Paint and Interaction to Next Paint across real devices, real connections, and real locations. Google's Chrome User Experience Report is the most widely used RUM dataset, and it feeds the field-data sections of PageSpeed Insights and the Core Web Vitals that affect ranking. Commercial tools like Datadog, New Relic, and SpeedCurve add custom dashboards, real-time alerts, and breakdowns by location, device, and browser that Google's monthly snapshots can't give you.