What is field data in Core Web Vitals (CrUX)?

Field data is performance measured in the browsers of real visitors as they use your site. For Core Web Vitals, Google collects it from opted-in Chrome users in the Chrome User Experience Report (CrUX). PageSpeed Insights and Search Console show it, and it decides whether your pages pass.

Why it matters

A lab test loads your page once in a fixed setup. Real visitors differ: older phones, patchy mobile networks, far-away locations, browser extensions and varied behaviour. Field data captures that spread, including interactions and scrolling that a scripted test never performs. This is why Search Console's Core Web Vitals report is based on field data rather than a lab score.

Field results are reported for LCP, INP and CLS at the 75th percentile of page loads, so a page is rated on what three in four visits experience or better.

How to see it

PageSpeed Insights. Enter a URL. The top block, "Discover what your real users are experiencing", shows field metrics for that URL if available, with a switch to show the whole origin (the entire site).
Search Console. Open the Core Web Vitals report to see groups of similar URLs with the status Good, Needs improvement or Poor, split by mobile and desktop.
CrUX tools. The data is also available through Google's CrUX dashboards and API for people who want to track trends.

What to know about its limits

It needs enough traffic. Pages or sites with too few visits from eligible users may show no field data. Then PageSpeed Insights may fall back to origin data, or show none.
It is a rolling window. The data covers a trailing period, roughly the last four weeks, so a fix takes time to show up fully.
It covers certain visitors. CrUX reflects Chrome users who have opted in to the relevant reporting, not every visitor on every browser.
It tells you what, not why. Field data shows a metric is poor but not which element or script caused it. Use lab tools such as Lighthouse and DevTools to investigate.

Common mistakes

Expecting field data to change the day after a deployment.
Treating the absence of data as a failing result.
Using only the origin summary when one template is the problem.
Comparing field numbers with a lab score as if they were the same measurement.

Frequently asked questions

What does CrUX stand for?

Chrome User Experience Report. It is a public dataset of real-user experience measurements gathered from Chrome browsers.

Why is there no field data for my page?

The page probably does not receive enough visits from users included in the dataset. New and low-traffic pages commonly lack it.

Is field data better than lab data?

They do different jobs. Field data tells you how real visitors fare, and lab data helps you reproduce and fix the cause. Use field first to find problems and lab to solve them.

Crawvix's scan checks whether real-visitor Core Web Vitals pass. To see a sample, Try the free website sample.