Digital Experience Monitoring
Digital Experience Monitoring covers browser and mobile real-user telemetry plus synthetic monitoring. The exam tests whether you can separate field data from lab data, read Core Web Vitals correctly, and design a synthetic check that proves a user journey works.
Core rules
- The browser agent captures page-load phases (DNS, TCP, request, DOM processing, render), AJAX calls, JavaScript errors, and sessions. Browser Pro adds deeper session and interaction data, including session replay where enabled.
- Core Web Vitals are field metrics at the 75th percentile: LCP ≤2.5s is good, INP ≤200ms is good (INP replaced FID), and CLS ≤0.1 is good. Report p75, not the mean; a fast average can hide a slow mobile cohort.
- Mobile monitoring captures crashes, handled exceptions, HTTP errors, network timing, and device/OS breakdowns. Mobile request telemetry correlates with backend traces when distributed tracing is configured.
- Synthetic monitors run ping, simple browser, scripted browser (Selenium), and API tests from public or private locations. Private locations reach internal apps; secure credentials keep secrets out of scripts. Monitors alert on failures and can enforce multi-step journeys.
Worked example
A retail team sees mobile LCP p75 = 3.8s, INP p75 = 150ms, CLS p75 = 0.03. Only LCP fails. Filtering browser page views to mobile and faceting by page shows the product page hero image is the LCP element. Preloading the hero and serving a smaller responsive image lowers LCP p75 to 2.2s. INP and CLS were already good, so no further work is justified by the data.
Traps
Do not use synthetic lab results to claim field Core Web Vitals pass. Do not average percentiles. A scripted browser that fails on a selector is a test-maintenance issue, not necessarily an app outage. Private-location checks are required for intranet URLs.