Field Data (Real User Monitoring)

Field dataReal User Monitoring (RUM) captures performance and experience data from real users during their actual visit. It provides so-called field data from real-world usage.Open glossary entry → (often collected as Real User MonitoringField data are performance measurements based on real users and their actual devices and connections. They show whether a performance problem is genuinely relevant.Open glossary entry →, RUM) are based on real visitors to a website and their actual devices, browsers and network conditions. They answer the question: do real users have a problem? This makes them the authoritative basis for assessing the Core Web VitalsCore Web Vitals are a set of Google metrics that measure real-world user experience in the areas of loading performance, interactivity and visual stability.Open glossary entry →, which are measured at the 75th percentileThe 75th percentile is the threshold at which at least 75 % of page views reach the good value. Core Web Vitals are assessed at this point, not at the average.Open glossary entry → of page views.

Typical sources of field data include:

• the Chrome UX Report (CrUX),
• PageSpeed Insights (field data section),
• the Core Web Vitals report in Google Search Console,
• your own Real User Monitoring or analytics with web vitals tracking.

Field data do not react immediately to changes: depending on traffic, it can take several weeks for improvements to become stably visible. Unlike lab dataLab data are produced in a simulated test environment with fixed device and network conditions. They help identify the technical causes of performance problems.Open glossary entry →, field data do not reveal the technical cause but the actual relevance of a problem.