How Are Rankings Determined on Web Vitals Leaderboard?

Rankings on Web Vitals Leaderboard are determined by Largest Contentful Paint (LCP), which the site treats as the most important metric for representing fast speed. When you add a URL or origin and view results, sites are ordered by how quickly their largest content renders, and the leaderboard uses real-world Chrome UX Report data rather than lab tests. The practical takeaway: a better rank means a shorter LCP, with top-performing sites rendering LCP in about 1.2 seconds.

What LCP measures

LCP measures when a user perceives that the largest content of a page is visible. The metric value represents the time duration between the user initiating the page load and the page rendering its primary content.

In other words, it is not a measure of when the first byte arrives or when the page becomes interactive. It is a measure of when the main content a user came for actually appears on screen.

Why LCP drives the ranking

The site states that, based on real website data, top-performing sites render LCP in about 1.2 seconds, so this metric is the most important to represent a fast speed. That is the basis for using LCP as the ranking metric rather than combining all four Web Vitals into a single score.

The other metrics shown alongside LCP — FCP, CLS, and INP — are displayed for context, but the ordering of sites follows LCP.

Where the numbers come from

The leaderboard uses the Chrome UX Report API. That dataset represents how real-world Chrome users experience popular destinations on the web, and CRUX aggregates user experience metrics by origin and URL for all websites known to Google's web crawlers.

Two consequences follow from this:

• Rankings reflect field data from actual Chrome users, not synthetic or lab measurements.
• A site with little or no CRUX coverage may return no data instead of a rank. The interface surfaces this as "Chrome UX Report data not found!"

How fresh the ranking is

CRUX data is a 28-day rolling average of aggregated metrics. The data shown at any given time is actually the past 28 days aggregated together, so a ranking reflects roughly the last month of user experience rather than the most recent day.

This matters when interpreting a rank: a recent performance fix will not move the leaderboard immediately, and a recent regression will not immediately drag it down.

Reading a result correctly

To compare fairly, keep the device filter consistent across the sites you are looking at, since mobile and desktop experiences can differ substantially.

Practical implications

• If you want to improve your position, focus on reducing LCP — that is the metric the ordering responds to.
• Expect a lag of up to about 28 days before changes are reflected, because of the rolling average.
• If your site does not appear, it likely lacks sufficient CRUX data rather than being excluded for another reason.
• Use the other metrics to diagnose why LCP is slow, but do not expect them to change your rank on their own.