What Do FCP, LCP, CLS, and INP Mean on Web Vitals Leaderboard?

Updated

Web Vitals Leaderboard ranks sites by the metrics Google uses to describe real user experience: FCP, LCP, CLS, and INP. All four come from the Chrome UX Report (CrUX), so they reflect how actual Chrome users experienced a site over the past 28 days — not a lab test run on demand. The leaderboard treats LCP as the headline metric, since it best represents perceived speed; top-performing sites render their largest content in about 1.2 seconds.

The four metrics

Metric Full name What it captures Unit
FCP First Contentful Paint When the first piece of content (text, image) becomes visible Time
LCP Largest Contentful Paint When the largest content element in the viewport finishes rendering Time
CLS Cumulative Layout Shift How much visible content unexpectedly moves during load Score
INP Interaction to Next Paint Responsiveness — the delay between a user interaction and the next visual update Time

FCP — First Contentful Paint

Marks the moment the user sees that the page is actually loading. It answers "did anything appear yet?" rather than "is the page useful yet?" A fast FCP reassures the user, but a page can have a good FCP and still feel slow if the main content arrives much later.

LCP — Largest Contentful Paint

Measures when the page's primary content — typically a hero image or large block of text — is rendered. This is the metric the leaderboard emphasizes: it approximates when the user perceives the page as loaded. The site notes that based on real website data, top-performing sites render LCP in about 1.2 seconds, which is why LCP carries the most weight in the ranking.

CLS — Cumulative Layout Shift

A score, not a duration. It accumulates every time visible elements shift position unexpectedly — a banner dropping in, a font swapping, an ad pushing text down. A low CLS means the page stays visually stable while loading, so users don't misclick or lose their place.

INP — Interaction to Next Paint

Captures responsiveness across the whole visit. It measures the latency from a user action (click, tap, key press) to the next frame the browser paints. A high INP means the page feels sluggish or unresponsive even if it loaded quickly.

Where the numbers come from

The leaderboard pulls from the Chrome UX Report API, which aggregates real-world Chrome usage for origins and URLs known to Google's crawlers. Because CrUX reports a 28-day rolling average, every figure is a trailing aggregate of the past 28 days — not a live measurement. A site with little Chrome traffic may return no data at all, which is why the leaderboard can show "Chrome UX report data not found!" for some URLs.

How to read a ranking

  • LCP drives the ranking. The leaderboard's stated logic is that LCP best represents fast speed, so expect LCP to dominate how sites are ordered.
  • Compare like with like. Rankings are grouped by device — mobile, desktop, and tablet — because performance differs sharply across them. A mobile ranking is not comparable to a desktop one.
  • Treat the other three as context. FCP, CLS, and INP explain why a site ranks where it does: a fast LCP with a poor CLS or INP still means a rough experience.
  • Remember the window. A site that shipped a fix yesterday won't show it until the 28-day average rolls forward.

In short: LCP tells you how fast the page feels, FCP how soon it starts, CLS how stable it stays, and INP how responsive it is — and the leaderboard uses LCP as its primary yardstick for speed.