web-vitals.pazguille.me

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.

Web Vitals Leaderboard is a free web tool that compares your site's real-world performance against other sites in your industry. You enter a URL or origin, and it ranks that site against others using Core Web Vitals metrics drawn from Google's Chrome UX Report (CrUX). It's useful when you want a quick, competitive read on speed and user experience rather than a deep diagnostic audit.

What it does

The tool's stated purpose is to be "the simplest way to understand how your website's performance compares to other sites in your industry." Instead of showing you raw lab data, it pulls field data — measurements from actual Chrome users — and places your site in a ranked list.

The interface accepts a URL or origin, then displays a ranked table with these columns:

You can filter results by device category: All devices, Mobile, Desktop, or Tablet.

Where the data comes from

The leaderboard uses the Chrome UX Report API. According to the site's FAQ, CrUX "represents how real-world Chrome users experience popular destinations on the web" and aggregates metrics by origin and URL for sites known to Google's crawlers.

Two consequences follow from this:

• Only popular sites appear. CrUX covers origins with enough real-user traffic to meet Google's reporting thresholds. Low-traffic or new sites may return no data — the tool shows "Chrome UX report data not found!" in that case.
• Data is a 28-day rolling average. The FAQ states the report aggregates the past 28 days together, so a recent fix won't show up immediately, and a recent regression won't either.

How rankings are determined

The FAQ explains that ranking is driven primarily by LCP (Largest Contentful Paint), which measures when a user perceives the largest content of a page as visible — the time between page load starting and primary content rendering. The site notes that top-performing sites render LCP in about 1.2 seconds, and treats LCP as the most important metric for representing fast speed.

FCP, CLS, and INP are displayed alongside it, so you can see whether a strong or weak rank comes from paint timing, layout stability, or interactivity.

When to use it — and when not to

Good fit:

• You want a fast, competitive benchmark against industry peers.
• You need to justify performance work with real-user data rather than synthetic scores.
• You're tracking whether a change moved your origin's 28-day average.

Poor fit:

• Your site is new or low-traffic — CrUX likely has no data for it.
• You need per-page, per-element diagnostics. This is a leaderboard, not a profiler; use Lighthouse, PageSpeed Insights, or your own RUM for that.
• You need same-day feedback on a deploy. The 28-day rolling window smooths out short-term changes.

Practical notes

• Enter the origin (e.g. example.com) when you want site-wide comparison; a full URL targets that specific page if CrUX has URL-level data for it.
• If you get the "data not found" message, it's a coverage limit of CrUX, not an error in your input.
• The site is built by Guille Paz and offers a "Support Me!" link; no pricing or account requirements are stated on the page.

Web Vitals Leaderboard pulls its numbers from the Chrome UX Report (CrUX) API, which reflects how real Chrome users actually experience sites on the web. The data is a 28-day rolling average, so any result you see represents the past 28 days of aggregated metrics rather than a live snapshot. This matters if you're using the leaderboard to judge whether your site is genuinely faster or slower than competitors: you're comparing a recent monthly trend, not a single test run.

The data source: Chrome UX Report (CrUX)

The leaderboard doesn't run its own synthetic tests. Instead, it queries the CrUX API, a Google dataset built from real-world Chrome users.

• Real user data, not lab data. CrUX captures field metrics from actual browsing sessions, so it reflects real devices, networks, and conditions rather than a controlled test environment.
• Aggregated by origin and URL. CrUX groups user experience metrics by origin (e.g., example.com) and by specific URL, for all websites known to Google's crawlers.
• Coverage depends on Google's crawlers. A site only appears if Google's crawlers know about it and enough real users visit it to produce reportable data.

Why you might see "Chrome UX report data not found!"

If the leaderboard returns that message, it means CrUX has no reportable data for the origin or URL you entered. Common reasons:

• The site is too new or gets too little Chrome traffic to meet CrUX's reporting thresholds.
• The origin isn't recognized by Google's crawlers.
• You entered a URL or origin that doesn't have aggregated data.

In that case, the leaderboard has nothing to rank — it isn't a bug in the tool so much as a gap in the underlying dataset.

How often the data updates

CrUX data is a 28-day rolling average of aggregated metrics. In practice:

• At any given moment, the numbers represent the past 28 days combined, not the last hour or day.
• The window slides forward over time, so results gradually change as older data drops out and newer data comes in.
• Because it's an average, a single slow day won't swing your score dramatically, and a single fast day won't either.

This is useful for trend comparison but means the leaderboard won't show the effect of a change you deployed minutes ago. If you just shipped a performance fix, expect the rolling average to reflect it only gradually.

How rankings are determined

The leaderboard ranks sites using Web Vitals metrics, with Largest Contentful Paint (LCP) as the most important for representing speed.

• LCP measures when a user perceives that the largest content of a page is visible — the time between the page load starting and the primary content rendering.
• Based on real website data, top-performing sites render LCP in about 1.2 seconds, which is the benchmark the ranking leans on.
• Other metrics shown alongside LCP include FCP, CLS, and INP, giving a fuller picture of loading, stability, and interactivity.

What this means for interpreting results

Use the leaderboard when you want an industry-relative, real-user view of performance over roughly the last month. Don't use it to validate a change you made today, and don't treat a missing result as a failing grade — it usually just means CrUX lacks enough data for that origin or URL.

Web Vitals Leaderboard returns "Oops.. Chrome UX report data not found!" when the URL or origin you entered has no matching record in the Chrome UX Report (CrUX). The tool does not measure your site itself — it only looks up an existing CrUX dataset, so a missing record means CrUX has nothing aggregated for that origin or URL, not that the tool is broken. This usually happens for low-traffic sites, brand-new domains, or URLs that don't match the exact origin CrUX tracks.

What the error actually means

The leaderboard pulls from the Chrome UX Report API, which aggregates real-world experience metrics from Chrome users for sites known to Google's web crawlers. When you add a URL or origin and click View Results, the tool queries that dataset. If no record comes back, it shows the "Chrome UX report data not found!" message instead of a rank table.

So the error is a data-availability problem, not a performance verdict. Your site may be perfectly fast and still produce this message if CrUX has never collected enough data for it.

Why your site may not appear in CrUX

The most common causes, roughly in order of likelihood:

• Not enough real-world traffic. CrUX only publishes data for origins and URLs with a sufficient volume of Chrome user visits. A site with little traffic won't qualify.
• The URL or origin doesn't match what CrUX tracks. CrUX aggregates by origin (for example, https://example.com) and by specific URL. Entering a path, a subdomain, or a slightly different hostname can miss the record.
• The site is new or recently changed. Data is a 28-day rolling average, so a newly launched or recently migrated domain may not have accumulated a full window yet.
• Google's crawlers don't know the site. CrUX covers destinations known to Google's web crawlers; a site that isn't crawled or indexed won't be represented.
• The page is private or gated. Pages behind a login or otherwise not publicly reachable by real Chrome users won't generate the aggregated data CrUX needs.

How to check and fix it

1. Confirm the exact origin. Enter the origin in the form CrUX uses, typically https://example.com with no trailing path. Try the bare origin first, then a specific URL if you need page-level data.
2. Verify the site has real Chrome traffic. If the domain is new, low-traffic, or internal-only, expect no CrUX record. There is no setting in the tool that can create one.
3. Re-check after the 28-day window. Because CrUX is a 28-day rolling average, a site that recently crossed the traffic threshold may only appear once enough data accumulates.
4. Test a known high-traffic origin. Enter a large public site to confirm the tool itself is working. If that returns a rank table, the issue is your site's CrUX coverage, not the leaderboard.
5. Use the device filter to narrow results. Once a record exists, you can switch between All devices, Mobile, Desktop, and Tablet to see how rankings differ by platform.

What to do if CrUX simply has no data for you

If your site genuinely lacks CrUX coverage, the leaderboard can't rank it — there's no workaround inside the tool. In that case:

• Use field-data alternatives that don't depend on CrUX volume thresholds, or rely on lab testing for a directional read on speed.
• Focus on the metric the leaderboard treats as most important: LCP. Based on real website data, top-performing sites render LCP in about 1.2 seconds, which is why LCP drives the ranking.
• Revisit the leaderboard later once your site has enough public Chrome traffic to enter the dataset.

The key takeaway: "Chrome UX report data not found" means CrUX has no aggregated record for the origin or URL you entered. Fix the input if it's a mismatch, or accept that the site needs more real-world Chrome traffic before it can be ranked.

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

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.