Core Web Vitals Lab Data
Lab data gives you controlled, reproducible performance measurements for regression detection. It's the foundation of continuous monitoring.
Core Web Vitals lab data is produced by running performance tests in a controlled environment with specified device and network conditions. Tools like Google Lighthouse, WebPageTest, and AuditJet's synthetic monitoring all produce lab data.
Lighthouse — the engine behind Google PageSpeed Insights and AuditJet — uses a fixed mid-range Android device emulation with 4G network throttling. These conditions are chosen to represent a typical user in emerging markets — not the fastest, not the slowest.
Lab data's primary value is regression detection. Because the test conditions are always the same, any change in lab scores between measurements reflects a real change in the page, not a variation in user conditions. When AuditJet detects a 500ms LCP regression in lab data, it means something changed on the page.
FAQ
What is Core Web Vitals lab data?
Lab data is performance measurements taken in a controlled environment with fixed device and network conditions. Lighthouse, PageSpeed Insights, and AuditJet's synthetic monitoring all produce lab data.
Why doesn't Google use lab data for rankings?
Lab data doesn't capture the true diversity of real user experiences. Google uses field data from CrUX for rankings because it reflects actual performance across the full distribution of devices and networks.
What are the Lighthouse test conditions?
Lighthouse simulates a mid-range Android device (Moto G Power equivalent) with 4G network throttling (10 Mbps download, 40ms RTT) and 4x CPU slowdown. This represents a typical mobile user in a developing market.
How does AuditJet use lab data?
AuditJet runs Lighthouse on a schedule and stores each result in a time series. When a metric regresses compared to the rolling 7-day baseline, it fires an alert. This continuous lab data monitoring catches regressions within hours of their occurrence.
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