Synthetic-Monitoring

Real User Monitoring (RUM) and Frontend Observability: Core Web Vitals, Error Tracking, and Session Replay

February 22, 2026

Rum-Implementation, Core-Web-Vitals-Measurement, Frontend-Error-Tracking, Session-Replay-Configuration, Frontend-Backend-Correlation

Rum, Real-User-Monitoring, Core-Web-Vitals, Frontend-Observability, Performance-Monitoring, Error-Tracking, Session-Replay, Synthetic-Monitoring, Web-Performance

Grafana-Faro, Sentry, Datadog-Rum, Google-Lighthouse, Web-Vitals-Js, Opentelemetry-Js, Grafana

What Real User Monitoring Measures#

Real User Monitoring (RUM) collects performance and behavior data from actual users interacting with your application in their real browsers, on their real networks, with their real hardware. Unlike synthetic monitoring, which tests a controlled scenario from a known location, RUM captures the full spectrum of user experience – including the user on a slow 3G connection in rural Brazil using a 4-year-old phone.

RUM answers questions that no amount of server-side monitoring can: How fast does the page actually load for users? Which JavaScript errors are users hitting in production? Where do users abandon a workflow? Which geographic regions experience worse performance?

Synthetic Monitoring: Proactive Uptime Checks, Blackbox Exporter, and External Probing

February 21, 2026

Observability

Intermediate

Synthetic-Monitoring-Setup, Blackbox-Exporter-Configuration, Uptime-Alerting, Ssl-Certificate-Monitoring

Synthetic-Monitoring, Blackbox-Exporter, Prometheus, Uptime, Probes, Ssl-Monitoring, Grafana, Alerting

Prometheus, Blackbox-Exporter, Grafana, Alertmanager

What Synthetic Monitoring Is#

Synthetic monitoring means actively probing your services on a schedule rather than waiting for users to report problems. Instead of relying on internal health checks or real user traffic to detect issues, you send controlled requests and measure the results. The fundamental question it answers is: “Is my service reachable and responding correctly right now?”

This is distinct from real user monitoring (RUM), which observes actual user interactions. Synthetic probes run 24/7 regardless of traffic volume, so they catch outages at 3 AM when no users are active. They provide consistent, repeatable measurements that are easy to alert on. The tradeoff is that synthetic probes test a narrow, predefined path – they do not capture the full range of user experience.