Ad metrics can be used to understand the impact of advertising on websites.
On September 16th 2026, Google introduced four new experimental metrics that measure how much of a page’s viewport, processor time and network data is taken up by advertising.
These new metrics are measured by Chrome itself and reported through the Chrome User Experience Report (CrUX).
Calibre collects ad metrics from CrUX and makes them available in the Core Web Vitals Test tool.
What do ad metrics measure?#
- Viewport ad density (
experimental_ad_density): The amount of ad content in the viewport while the page is in the foreground. Reported as a percentage from 0 to 100. - Viewport ad count (
experimental_ad_count): The number of separate ad units visible. - Total CPU usage by ads (
experimental_ad_cpu): JavaScript execution time consumed by ad frames. CPU time for ad scripts in the main frame is excluded. - Total network usage by ads (
experimental_ad_kilobytes): How much data transferred for ad frames and ad resources such as scripts, images and stylesheets.
How are ad metrics calculated?#
All four metrics require the page to be in the foreground, with ads visible in the viewport. Google’s calculation examples:
- Ad density: If ads cover 50% of the viewport for 5 seconds and then 0% for 5 seconds, the reported value is 25%.
- Ad count: If 2 ads are visible for 5 seconds and then 0 ads for 5 seconds, the reported value is 1.00.
You can read an explainer about how ad detection works at a more technical level on the Chrome for developers blog.
Chrome’s ad detection is automatic and imperfect: it can miss ads, and it can count other content as an ad.
Where ad metrics are available#
Google states that "Pages and origins without at least one authorized seller defined in ads.txt file won’t have ad metrics data in CrUX." A site can have an ads.txt file and still have no ad metrics data, because the standard CrUX eligibility criteria also apply.
You can find CrUX ad metrics in the following places:
- Calibre’s free core web vitals checker tool: Ads are displayed in the Advertising section when available. If ad metrics are unavailable, the section is not displayed.
- CrUX APIs: The CrUX API and CrUX History APIs.
- Chrome DevTools: The same metrics can be seen in DevTools under Application, in the Ads panel.
Are there recommendations or thresholds for ad metrics?#
No. Google published the ad metrics with no recommended thresholds and no good, needs improvement or poor buckets. They are not Core Web Vitals and have no effect on search ranking. Google’s stated intent is to start a conversation about improving ads on the web.
You can use ad metrics to easily understand the weight of detected ads on pages.