Real user monitoring
Real user monitoring, often shortened to RUM, measures how your service actually performs for the people using it. Instead of a scripted probe, lightweight instrumentation in the page or app reports timing and errors from real sessions.
What it captures
- Page load and interaction timing as experienced on real devices and networks
- The spread across browsers, geographies, and connection speeds
- Errors and crashes that only appear under real conditions
RUM shines because it reflects the true distribution of your users. A test from a fast office network hides what a phone on a weak signal experiences. With real data you watch percentiles, since the slow tail is where frustration lives.
Strengths and limits
RUM cannot warn you during an outage with zero traffic, because there are no users to report. It also depends on the volume of sessions to be statistically meaningful for rare pages. That is why teams pair RUM with synthetic monitoring. Synthetic gives a steady baseline, while RUM tells you what users truly feel.
Key idea
Real user monitoring reports timing and errors from actual sessions, revealing the true distribution of experience that synthetic checks cannot.