Lab Data

Lab dataLab data are produced in a simulated test environment with fixed device and network conditions. They help identify the technical causes of performance problems.Open glossary entry → are collected in a controlled, simulated test environment, for example with defined device, CPU and network settings. They answer the question: where might the problem lie technically? This makes them especially useful for diagnosis and troubleshooting.

Typical sources of lab data include:

• LighthouseLighthouse is an open-source diagnostic tool from Google that audits a page's performance, accessibility and other quality aspects in a simulated lab environment.Open glossary entry →,
• the Chrome DevTools,
• WebPageTest,
• the lab section of PageSpeed Insights,
• local performance tests.

The distinction from field dataReal User Monitoring (RUM) captures performance and experience data from real users during their actual visit. It provides so-called field data from real-world usage.Open glossary entry → is important: lab data show possible technical causes but do not replace real user dataField data are performance measurements based on real users and their actual devices and connections. They show whether a performance problem is genuinely relevant.Open glossary entry →. A good workflow is therefore to first check field data to see whether a problem is relevant, then use lab data to diagnose the cause. Because lab data and field data reflect different conditions, their values can differ significantly.