What Is RUM vs. Synthetic Testing?

Real user monitoring (RUM) and synthetic testing are two different approaches for collecting data and optimizing performance of application and website performance. Both methodologies provide valuable insight into user experience and application performance, and both can uncover potential performance issues.

When deciding between RUM vs. synthetic testing, it’s important to understand the benefits and limitations of each performance monitoring approach, and the kinds of data that real-time user monitoring and synthetic monitoring can capture

RUM monitoring is a form of passive monitoring that collects data about user interactions with websites and applications in real time. RUM tools such as Akamai mPulse embed lightweight software like JavaScript tags into application code to gather performance data on a wide range of metrics. These may include data on page load times, information about user behavior, data on the geographic location of users, and performance metrics around latency and API response times. RUM dashboards offer full visibility into real-world user experiences, enabling teams to effectively identify bottlenecks and address performance problems that may impact end-user experiences with a website or application.

Synthetic testing, or synthetic monitoring, is an active approach to application and web performance tests. Synthetic monitoring tools use scripts to simulate user actions within an application or user journeys on a website. Synthetic testing is performed in a controlled environment, providing consistent baseline conditions for benchmarking and comparison. Synthetic testing enables teams to use a controlled set of variables to test for various geographies, networks, browsers, and devices.

Benefits of RUM

• Real-world insights: RUM tools provide invaluable insight into actual user behavior and long-term trends that synthetic testing may not anticipate or test for. This includes data on how performance metrics like page load times and API responsiveness impact actual experiences like checkout procedures on ecommerce sites.
• Problem detection: With capabilities for real-time observability and instant alerts, RUM enables IT teams to quickly troubleshoot and remediate performance issues that are encountered by users in real-world conditions.
• Optimization for geographies and devices: RUM tools help teams understand how performance varies across different locations and devices, enabling targeted optimization.
• Understand user engagement: RUM solutions can better correlate application performance with user engagement and key performance indicators for business objectives.
• Improve conversion rates: By tracking data user engagement and conversion metrics, RUM enables teams to enhance the user’s journey through a website to increase conversions.

Benefits of synthetic testing

• Regular testing: Synthetic monitoring can run tasks at scheduled intervals — or run 24/7 — to proactively uncover potential issues before they affect actual users.
• Benchmarking: Synthetic testing can establish baseline performance against predefined metrics, helping teams continually optimize web performance.
• Availability monitoring: Synthetic testing methods help avoid downtime by ensuring that websites and web applications are available and performing well in different locations around the world before they’re exposed to increases in real user traffic.
• Pre-production testing: Synthetic monitoring enables development teams to test websites and applications before they are moved to production environments.
• Tracking SLA compliance: With synthetic testing, teams can track potential breaches of service-level agreements.

Limitations of RUM

• Unable to be proactive: RUM is inherently reactive, identifying issues only after they have affected actual users.
• Requires traffic: RUM works best when there is sufficient traffic for applications, websites, and mobile apps.
• Data volumes: The amount of data collected from real users can quickly become large and unwieldy to process and manage.
• Data privacy concerns: Collecting real user data may result in issues with data privacy.

Limitations of synthetic testing

• Lack of real user input: Synthetic testing can’t capture the full complexity and unpredictability of real-world user interactions and the varied environments they occur in.
• Predictability: Because synthetic tests are created by development teams and administrators that may have preconceived ideas about how a site or application works, synthetic tests may be blind to certain kinds of user experience issues.

Choosing between RUM vs. synthetic testing typically comes down to the specific use cases and testing objectives of development teams and IT administrators.

• Optimizing user experiences: RUM provides greater detail about the real-time experiences of users, enabling teams to better optimize digital experiences.
• Ensuring uptime and availability: Synthetic testing is ideal for constantly ensuring that websites and applications are available for users in different locations.
• Pre-launch testing: Synthetic testing is also preferable for development teams seeking to test functionality before websites or applications are launched.
• User engagement: RUM is a better tool for tracking user engagement and correlating it with conversions.
• Early detection: Both RUM and synthetic testing can help teams to quickly pinpoint and remediate issues. Synthetic testing excels at identifying problems before they are encountered by active users, while alerts from RUM can provide teams with immediate notification when users are encountering problems.
• Troubleshooting: There’s no clear winner in RUM vs. synthetic testing when it comes to troubleshooting the root cause of issues and outages — they can be used in a simultaneous and complementary way to streamline troubleshooting efforts. When synthetic tests fail to uncover an issue, RUM data will reveal the real-time impact on end-user experiences. When RUM data uncovers a performance issue, synthetic tests can replicate the problem across networks and geographic locations to proactively remediate problems.

Combining RUM and synthetic testing enables teams to implement the most comprehensive monitoring strategy.