Synthetic vs Real User Monitoring

By Engineering Team | 2026-04-09 | Engineering

# Synthetic vs Real User Monitoring

In the world of application performance monitoring (APM), two primary techniques are used to track the user experience: synthetic monitoring and real user monitoring (RUM). While both share the same goal—ensuring a high-performing and reliable application—they work in fundamentally different ways and provide different types of insights. Understanding the differences between synthetic monitoring and RUM is essential for building a comprehensive monitoring strategy that provides deep visibility into your application's performance and user experience.

What is Synthetic Monitoring?

Synthetic monitoring involves using automated scripts or "bots" to simulate user interactions with your application from various geographical locations. These scripts follow predefined paths (e.g., logging in, searching for a product, checking out) and record performance metrics like response times, error rates, and availability. Synthetic monitoring is primarily focused on "known unknowns"—the issues that you know can happen and that you have specifically designed your monitoring system to detect.

Key Characteristics of Synthetic Monitoring:

**Automated and Predictable:** Synthetic monitoring uses automated scripts that follow predefined paths, providing predictable and consistent performance data.

**Proactive:** Synthetic monitoring can detect issues before they impact real users, allowing you to take proactive steps to resolve them.

**Geographical Visibility:** Synthetic monitoring allows you to simulate user interactions from various geographical locations, providing insights into regional performance differences.

**Focus on Availability and Baseline Performance:** Synthetic monitoring is excellent for tracking application availability and establishing performance baselines.

What is Real User Monitoring (RUM)?

Real user monitoring (RUM) involves collecting performance data from actual users as they interact with your application in the real world. This data is typically collected using a small piece of JavaScript code injected into your application's frontend. RUM provides deep insights into how your application performs for real users across a wide range of devices, browsers, and network conditions. RUM is primarily focused on "unknown unknowns"—the issues that you didn't anticipate and that your synthetic monitoring system might miss.

Key Characteristics of Real User Monitoring (RUM):

**Actual User Data:** RUM collects performance data from real users, providing the most accurate picture of your application's performance in the real world.

**Comprehensive Visibility:** RUM provides insights into application performance across a wide range of devices, browsers, and network conditions.

**Focus on User Experience and Behavior:** RUM helps you understand how application performance impacts user behavior and satisfaction.

**Reactive:** RUM is primarily reactive, telling you when an issue has already impacted real users.

The Relationship Between Synthetic Monitoring and RUM

Synthetic monitoring and RUM are not mutually exclusive; they are complementary. Synthetic monitoring provides a consistent, proactive way to track application availability and baseline performance. RUM provides the deep, real-world insights needed to understand how application performance impacts real users. A robust monitoring strategy requires both synthetic monitoring and RUM.

When to Use Synthetic Monitoring

Use synthetic monitoring for:

**Tracking Application Availability:** Ensure that your application is always up and accessible.

**Establishing Performance Baselines:** Track performance trends over time and identify significant changes.

**Testing New Features and Configurations:** Verify that new features and configurations are functioning correctly before they are released to real users.

**Monitoring Third-Party Services:** Track the performance and availability of third-party APIs and services that your application relies on.

**Benchmarking Against Competitors:** Compare your application's performance against your competitors' applications.

When to Use Real User Monitoring (RUM)

Use RUM for:

**Understanding Real-World Performance:** Gain deep insights into how your application performs for real users across a wide range of conditions.

**Identifying Performance Bottlenecks for Specific User Segments:** Identify performance issues that only impact specific devices, browsers, or geographical regions.

**Analyzing the Impact of Performance on User Behavior:** Understand how application performance impacts user engagement, conversion rates, and retention.

**Troubleshooting Complex, Real-World Issues:** Identify the root cause of issues that only manifest for real users in specific conditions.

**Prioritizing Performance Optimizations:** Use RUM data to identify the performance optimizations that will have the greatest impact on your users.

Best Practices for a Comprehensive Monitoring Strategy

To build a robust monitoring strategy that leverages both synthetic monitoring and RUM, follow these best practices:

**Implement Both Synthetic Monitoring and RUM:** Use both techniques to gain a comprehensive view of your application's performance and user experience.

**Integrate Your Data:** Integrate your synthetic monitoring and RUM data into a single, cohesive view.

**Set Up Meaningful Alerts:** Alert on actionable issues from both synthetic monitoring and RUM. Use thresholds based on historical data to reduce false positives.

**Regularly Review and Optimize:** Monitoring is an ongoing process. Regularly review your monitoring data, identify areas for improvement, and optimize your monitoring strategy.

**Focus on User Experience:** Ultimately, the goal of monitoring is to ensure a great user experience. Track metrics that reflect the user's experience, such as application latency and response times.

**Foster a Culture of Observability:** Encourage your entire engineering team to use both synthetic monitoring and RUM data to improve their code and infrastructure.

**Use Open Standards:** Use open standards like OpenTelemetry to ensure interoperability between different monitoring tools and services.

Conclusion

Synthetic monitoring and real user monitoring are both essential for maintaining high-performing and reliable applications. While synthetic monitoring provides a consistent, proactive way to track application availability, RUM provides the deep, real-world insights needed to understand how application performance impacts real users. By embracing both techniques and following best practices, you can build a more resilient, efficient, and intelligent monitoring strategy that ensures system reliability and delivers exceptional user experiences. As applications continue to grow in complexity, the combined power of synthetic monitoring and RUM will become increasingly critical for organizations that want to thrive in the fast-paced digital landscape.

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