Why a 'green' lab score still failed real users

Why a 'green' lab score still failed real users

There are two kinds of speed data. Lab data is a test in a controlled lab, on one device. Field data is what real visitors actually felt, gathered over 28 days. Think of lab data like a flight simulator and field data like a real flight in real weather.

A shop celebrated a 95 lab score in PageSpeed Insights, but Search Console still flagged the page as poor. The mismatch?

— Lab tested on fast desktop simulation.
— Field data showed real visitors on older phones with weak signal.
— Their LCP in the field was 3.4s, not the lab's 1.1s.

The fix targeted real conditions: smaller images, fewer scripts. Field LCP dropped to 2.1s.

Try this: in PageSpeed Insights, always read the top 'Field Data' box first. That's the score Google ranks on.