What is synthetic monitoring and how does it differ from real user monitoring (RUM)?

Synthetic monitoring (also called active monitoring) involves simulating user interactions with your application using scripted probes that run on a schedule, independent of real user traffic. The probes check that key user journeys — login, checkout, search — work correctly and measure their performance. Tools like Datadog Synthetics, Pingdom, Grafana k6, and AWS CloudWatch Synthetics run these scripts from multiple geographic regions around the clock.

The advantage of synthetic monitoring is that it detects issues even when real user traffic is zero — overnight, during off-peak hours, or before a region is publicly available. It also provides a consistent, reproducible baseline since the same script runs every time, making performance regressions easy to spot.

Real User Monitoring (RUM) collects telemetry from actual user browsers or mobile apps as they interact with your application. JavaScript agents (Datadog RUM, New Relic Browser, Google Analytics) capture page load times, core web vitals (LCP, CLS, FID), JavaScript errors, and user session data. RUM reflects the actual diversity of user environments: different browsers, network conditions, geographies, and device capabilities.

The two approaches are complementary. Synthetic monitoring provides consistent baselines and catches regressions before users see them; RUM reveals how real users across the globe experience your application and surfaces issues that synthetic scripts cannot replicate (e.g., third-party script failures on specific browser versions).

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