 Kevin K. Lee [X](https://twitter.com/kevinkiklee) [GitHub](https://github.com/kevinkiklee)
Published: September 15, 2026, Last updated: November 2, 2026
> [!WARNING]
> **Experimental:** Ad metrics are [experimental metrics](https://developer.chrome.com/docs/crux/methodology/metrics#experimental-metrics), and they may evolve based on user feedback.
The Ad Weight: CPU metric describes the CPU time consumed by ads, which may impact page performance.
## How Chrome calculates Ad Weight: CPU
Ad Weight: CPU is measured throughout the life of the page visit. It is the sum of all JavaScript CPU thread execution time (in milliseconds) consumed by ad frames and its subresources, computed as:
$$ \\text{CPU Weight} = \\text{Sum}\\left(\\text{execution time of all ad frames}\\right) $$ Ad Weight: CPU calculation
> [!NOTE]
> **Note:** The CPU time was originally measured for ad frames only and excludes CPU time for main frame ad scripts. From Chrome 159 this will include the CPU time for main frame ad scripts, which should be reflected in CrUX metrics from January 2027.
Ad Weight: CPU is reported in milliseconds as an integer.
The [Chrome User Experience Report (CrUX)](https://developer.chrome.com/docs/crux) aggregates data across all eligible Chrome users, and provides a 75th percentile number across those page views. Only pages with ads are considered for the CrUX ad metrics. Pages and origins [without at least one authorized seller defined in `ads.txt` file](https://developer.chrome.com/docs/ads/methodology#reporting_scope) won't have ad metrics data in CrUX. This data is available at the URL and origin-level, subject to the [CrUX eligibility criteria](https://developer.chrome.com/docs/crux/methodology).
## Collecting Ad Weight: CPU through JavaScript
There are challenges reporting across cross-origin iframes which most ads are delivered through. Therefore, there is no JavaScript API to allow similar detection for Real User Monitoring (RUM) tooling.
## Tooling
Ad Weight: CPU is available in [CrUX Vis](https://cruxvis.withgoogle.com/#/?view=ads&url=https%3A%2F%2Fwww.example.com), the [CrUX API](https://developer.chrome.com/docs/crux/api), [CrUX History API](https://developer.chrome.com/docs/crux/history-api), and the [DevTools Ad panel](https://developer.chrome.com/docs/ads/detection#devtools_support). To learn more about using these tools, see the [CrUX ad metrics tooling guide](https://developer.chrome.com/docs/ads/tooling).
We are working on adding the ad metrics to the [CrUX dataset on BigQuery](https://developers.google.com/web/tools/chrome-user-experience-report/bigquery) to enable users to query and analyze the ad metrics using SQL.
## Feedback
If you have any questions or feedback regarding ad metrics, reach out to us at the [Chrome UX Report Google Group](https://groups.google.com/a/chromium.org/g/chrome-ux-report).