Digital Experience Monitoring
Digital Experience Monitoring
This domain covers what the end user actually experiences: real-user browser and mobile telemetry, plus synthetic checks that simulate traffic when no real user is present.
Core rules
- Browser monitoring is delivered by a JavaScript agent injected in the page head (copy/paste snippet, npm bundle, or automatic injection through the APM agent). Browser Pro adds AJAX calls, JavaScript errors, session traces, and sampled session replay; Browser Lite gives page-load timing only.
- Core Web Vitals: LCP (largest contentful paint, good at 2.5 s or less), INP (interaction to next paint, good at 200 ms or less, which replaced FID in 2024), and CLS (layout shift, good at 0.1 or less).
- Page load timing splits a page view into DNS, connect, request/response, DOM processing, and page render; the slow segment points at the culprit.
- Synthetics types: ping (URL reachability only, no browser), simple browser (limited scripted clicks and form fills), scripted browser (full Selenium WebDriver JavaScript), and API test (multi-step HTTP calls with assertions, no browser).
- Monitors run from public locations or private locations you host; secure credentials keep secrets out of scripts; results feed SLA reports and alerts.
- Mobile agents (Android, iOS, hybrid) report crashes, handled exceptions, network requests, and version-level comparisons.
Worked example
A team must verify a three-page checkout that requires typing a coupon code and confirming a banner appears. Ping cannot execute JavaScript, and an API test cannot render the UI, so a scripted browser monitor is the right choice; a separate API test is added to watch the checkout endpoint's response time.
Traps
- Expecting ping monitors to catch JavaScript errors.
- Using a simple browser monitor for loops or complex selectors; that needs scripted browser.
- Quoting FID as the responsiveness metric when INP is current.
- Forgetting that private locations require the containerized minion and outbound access to New Relic.