Glossary
Field data
Measurements from your real visitors, not a simulation.
What it is
Field data is performance measured on actual visitors' devices and networks, aggregated by the Chrome UX Report. It is the data behind Search Console's Core Web Vitals report, and it covers a rolling 28-day window.
Why it costs you money
A lab score is one simulated device with no cache, no consent banner and no logged-in state. Your customers are a spread of devices on varying connections. When the two disagree — and they usually do — field data is the one describing the store your customers actually have.
How to check it yourself
Search Console reports it by page group. Sites without enough traffic have none, which is a sample-size limitation rather than a verdict.
Where this matters