CrUX Ad Metrics: Chrome Now Publishes How Heavy Your Ads Are

The Short Answer: What Changed

On 15 September 2026 Google added four experimental ad metrics to the Chrome UX Report (CrUX), the public dataset built from real Chrome users. They are Ad Count, Ad Density, Ad Weight: CPU and Ad Weight: Network. For the first time, how heavy your ads are is a public number that anyone can look up for your site, the same way they already look up your Core Web Vitals.

Two things matter before anything else. Google says plainly that these metrics are not part of Core Web Vitals and have no suggested targets or thresholds. So they do not feed rankings today. But they describe the exact thing that usually breaks the metrics that do: the ads.

Ad Metrics by the Numbers

Like every CrUX metric, the values come from real visits over a rolling 28 day window, and the API returns the 75th percentile. Data comes from Chrome on Windows, macOS, Linux, ChromeOS and Android. Chrome on iPhone, Android WebView apps and other Chromium browsers are not included, so a site whose audience is mostly iPhone users will see a thinner sample.

The Four Metrics Explained

Ad Count

This is how many separate ads a visitor actually sees on screen, averaged across the visit as they scroll. It is not how many ad slots exist in your HTML. A page with twelve slots where most never scroll into view can score lower than a page with four slots stacked in the first two screens. That makes it a good measure of what a reader lives through rather than what an ad server was asked for.

Ad Density

Density is the share of the screen covered by ads, sampled while the person reads. This is the one publishers will feel first, because it maps directly onto the Coalition for Better Ads standard, which treats mobile pages where ads take up more than 30 percent of the content as a bad experience. Until now you had to estimate that by hand. Now Chrome measures it on real phones.

Ad Weight: CPU

This is the processing time ads cost the device: downloading, parsing and running ad scripts and their creatives. It is the metric most closely tied to INP, because every millisecond an ad script holds the main thread is a millisecond a tap or click waits. Harry Roberts of CSS Wizardry points out one detail worth knowing: ad scripts running in your main frame are not counted, so a header bidding wrapper that runs in the page itself can escape this number while still slowing the page.

Ad Weight: Network

This is the compressed bytes your ads transfer. On a slow phone connection every kilobyte of ad code competes with your hero image, which is why heavy ad stacks so often show up as poor LCP on mobile while desktop looks fine.

Where to Find Your Numbers

Google made the data available in four places on day one, with a fifth promised:

• CrUX Vis at cruxvis.withgoogle.com, the free dashboard, which shows trends across roughly 40 weeks and refreshes every Monday.
• The CrUX API, which returns the latest 28 day snapshot for a URL or a whole origin, updated daily.
• The CrUX History API, which returns weekly time series covering about six months.
• The Ad panel in Chrome DevTools, for inspecting which frames Chrome treats as ads on a page you have open.
• BigQuery is not there yet. Google says it is working on adding the ad metrics to the public dataset.

Google also says data availability will grow over the month after launch, so if your origin shows nothing today, check again in a few weeks before assuming you are not eligible.

Query It Yourself

If you already have a CrUX API key, one request returns all four numbers for your whole site:

curl -s "https://chromeuxreport.googleapis.com/v1/records:queryRecord?key=YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "origin": "https://example.com",
    "formFactor": "PHONE",
    "metrics": [
      "experimental_ad_count",
      "experimental_ad_density",
      "experimental_ad_cpu",
      "experimental_ad_kilobytes"
    ]
  }'

Swap origin for url to check a single page, and swap queryRecord for queryHistoryRecord to get the weekly trend. Run it for PHONE first. Ad problems are almost always worse on mobile, for the same reasons we covered in why sites pass on desktop but fail on mobile.

How Ads Hit LCP, CLS and INP

The new numbers are not scored, but the damage they describe lands squarely on the three metrics that are.

Layout shift from ads is the most common case we see. The fix is to hold the space before the ad arrives:

.ad-slot-top {
  min-height: 250px;   /* the most common creative height for this slot */
  contain: layout;
}

You can watch this exact problem happen, and the fix work, in our CLS visualizer. For the full list of layout shift causes see how to fix CLS, and for the script side, our third party scripts guide covers ad tags alongside analytics and chat widgets. The free script auditor ranks every external script on a page by the time it costs.

What to Do This Week

1. Pull your baseline now. Save your four numbers from CrUX Vis today. Experimental metrics change, and a dated baseline is the only way to prove later that your changes worked.
2. Compare against your vitals. If Ad Weight: CPU is high and INP is failing, the ad stack is your first suspect. If density is high and CLS is failing, check slot reservation.
3. Check your worst templates, not your homepage. Article pages usually carry the most ads. Query a few top article URLs directly.
4. Talk to your ad partner with numbers. This is the real change. "Your ads are heavy" was an opinion. "Your ads cost our readers this many milliseconds of CPU at the 75th percentile, per Chrome's own data" is a fact your partner can act on.

Frequently Asked Questions

What are CrUX ad metrics?

They are four experimental measurements Google added to the Chrome UX Report on 15 September 2026: Ad Count, Ad Density, Ad Weight: CPU and Ad Weight: Network. They describe how many ads real Chrome users see on a page, how much of the screen those ads cover, and how much CPU time and network data the ads consume.

Do CrUX ad metrics affect Google rankings?

Not directly. Google states that the ad metrics are not part of Core Web Vitals and have no suggested targets or thresholds. They can still hurt you indirectly, because heavy ads are a common cause of poor LCP, CLS and INP, which are used in ranking.

Where can I see my site's ad metrics?

In CrUX Vis, the CrUX API, the CrUX History API and the Ad panel in Chrome DevTools. Google says the metrics are coming to the CrUX BigQuery dataset later.

What are the CrUX API names for the ad metrics?

experimental_ad_count, experimental_ad_density, experimental_ad_cpu and experimental_ad_kilobytes. Request them in the metrics array of a queryRecord or queryHistoryRecord call.

Why does my site show no ad data?

CrUX only publishes data for origins and pages with enough real Chrome traffic, and Google said availability would increase over the month after launch. Visits from Chrome on iPhone and from Android WebView apps are not counted either.

What is a good Ad Density?

Google gives no threshold. The closest public benchmark is the Coalition for Better Ads standard, which treats mobile pages where ads take up more than 30 percent of the content as a poor experience.

How do I reduce ad related layout shift?

Reserve the space before the ad loads, usually with a min-height on the slot that matches the most common creative size, and avoid inserting ads above content the reader is already looking at.

The Bottom Line

Ad weight used to be something publishers argued about with no shared number. Since 15 September 2026 Chrome publishes it for everyone to see, measured on real visits. It does not change your ranking today, but it shows exactly where your LCP, CLS and INP problems come from on ad supported pages. Save your baseline now, fix slot reservation and script timing first, and take the numbers to your ad partner.