Synthetic monitoring provides controlled baselines, while RUM reveals real-world performance. But when should you use each tool?

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Synthetic monitoring provides controlled, predictable performance baselines and uptime checks, while Real User Monitoring (RUM) captures actual user experiences across diverse devices, networks, and geographies. Synthetic tests excel at pre-deployment validation, CI/CD integration, and SLA tracking, but miss real-world chaos like third-party scripts and varied network conditions. RUM reveals device-specific issues, regional performance problems, and true Core Web Vitals distributions that affect end users. The most effective approach combines both: synthetic for proactive testing and quick incident detection, RUM for understanding real-world impact and user experience optimization. When investigating backend slowdowns, pairing synthetic API tests with RUM's distributed tracing connects infrastructure bottlenecks to actual user impact.

When To Use Synthetic Monitoring vs. Real User Monitoring

1. Launching a New Page or Feature → Start With Synthetic

2. Regional or Device-Specific Complaints → RUM

3. Tracking Availability and Uptime SLAs → Synthetic

4. Optimizing Core Web Vitals and Real-World UX → RUM

5. Investigating Backend or API Slowdowns → Use Both