To provide consistent measurement and align with industry standards, we are updating our approach to impression measurement for display traffic bought from Authorized Buyers or Open Bidders on Google Ad Manager and AdSense.
In Google Ad Manager and AdSense, impression measurement for display inventory will switch from the count-on-download (COD) to the begin-to-render (BTR) methodology starting in February 2027. No action is needed from Authorized Buyers, Open Bidders, or SDK Bidders.
We expect this change to increase the effectiveness of in-scope impressions due to the stricter billable methodology, since the impressions will still occur as long as publishers have supply.
Overview
Count-on-download involves counting an impression when an ad starts to download to a user’s device. Begin-to-render counts an impression when the ad creative has successfully loaded and has started to render on the user’s device. Begin-to-render presents a greater likelihood that the user can view the ad. To learn more about BTR, visit the IAB’s desktop display measurement guidelines.
Currently, Ad Manager and AdSense already use or are compliant with begin-to-render for native, app, and video inventory impression counting. The shift to count display ads via BTR unifies impression counting for all inventory types.
Here’s a breakdown of the current and future methodology use:
| Inventory type | Current methodology | Future methodology (coming February 2027) |
|---|---|---|
| Display: Banner Mobile web, Desktop, CTV |
Count-on-download (COD) | Begin-to-render (BTR) |
| Display: Non-banner (such as Native and Interstitial) |
BTR compliant | |
| App | 1-pixel (BTR compliant) | |
| Video | 1st frame (BTR compliant) | |
Benefits of begin-to-render for display ads
The switch to BTR provides the following benefits:
- BTR is the industry standard and preferred method of impression counting.
- BTR aligns impression measurement methodologies with buy-side platforms.
Timeline for the change
February 2027: Ad Manager and AdSense impression measurement will shift from count-on-download (COD) to begin-to-render (BTR) for display inventory on web, mobile web, and CTV banner. No action is required.