Real User Monitoring (RUM)

Real user monitoring (RUM) collects performance observations from actual visits to a live website, often using browser APIs or a JavaScript measurement library. It can report loading delays, responsiveness, navigation timing, and other user-experience signals across different devices and network conditions. Because it observes real traffic, RUM reveals problems that may not appear in a controlled office test.

RUM differs from synthetic or laboratory monitoring, where a scripted test uses a selected device, network profile, and location. Neither method replaces the other: lab testing helps reproduce problems and compare builds, while field data helps prioritize issues affecting actual visitors. RUM data can also be incomplete or skewed by sampling, browser limitations, consent choices, or a site's visitor mix.

A company's RUM implementation is not automatically identical to Google's Chrome User Experience Report (CrUX). CrUX aggregates eligible Chrome experience data using its own methodology. Teams should compare definitions, time ranges, and population coverage before interpreting differences between dashboards.