What is the difference between PageSpeed Insights and actual user experience?

PageSpeed Insights from Google delivers two fundamentally different kinds of data that are often confused. The lab data comes from a synthetic test in a controlled environment: a standardized mid-range device, a throttled network connection, a single page load. It is reproducible and ideal for diagnosing specific problems. The field data from the Chrome User Experience Report (CrUX), on the other hand, reflects how your real visitors experience the page over a 28-day window, with their actual devices, networks and locations.

In practice the two often diverge: a page may look slow in the lab but show good field data because real visitors access it on fast connections. For Google, what ultimately counts is the field. That is why every performance analysis we run draws on both sources, using lab data to find root causes and field data as the measure of success.