Publishers! You might want to keep this in mind to stay ahead. Google has announced that, starting February 17, 2027, impression measurement for display inventory will change in Google Ad Manager and AdSense from the count-on-download (COD) method to begin-to-render (BTR).
In simpler terms, Google will stop counting an impression the moment an ad starts downloading and start counting it only once the ad actually begins to render on screen for a more precise measurement of ad visibility. You can check the full documentation here.
Why is Google implementing this change?
According to Google, this is an industry-wide standardization move, not a company-specific policy shift, since Google already uses this method (BTR) for native, app, and video inventory. This is display catching up to those formats to unify the impression counting methodologies across different inventories. It also makes impression measurement more consistent with demand-side platforms.
What’s actually changing: Differences between COD and BTR
This change applies specifically to display banner inventory on web, mobile web, and CTV. Native, interstitial, app, and video formats already measure impressions using begin-to-render, so they’re not affected by this update.
With this change, Google raises a stricter, more accurate bar for what counts as an impression. The main difference between the old and new approaches comes down to when an impression is counted:
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- Old method (count-on-download aka COD): an impression counts when the ad creative starts loading, even if the user scrolls away before it ever shows.
- New method (begin-to-render aka BTR): an impression counts only once the creative has loaded and started rendering visibly. This indicates a higher likelihood that the user will see the ad.
What this means for publishers
Google has reported that it’s possible publishers might notice a potential decrease in total display impressions. This isn’t because traffic or demand changed, but because measurement is getting more precise. The change will roll out automatically in February 2027, meaning publishers won’t have to do anything to their setup. However, they can prepare for any impact this change might cause. Next up, we’ll discuss how.
What publishers should do to prepare
As a more rigorous measurement standard, publishers need to keep in mind that impressions will be counted at a later stage of the ad serving process (once rendering starts instead of once downloading begins). For that, it’s important to prioritize performance during rendering. Here’s what Google recommends:
- Run a before and after estimate now: Ad Manager publishers can pull a report comparing current count-on-download impressions vs. begin-to-render impressions (Google recommends using data from after August 12, 2026) to see the likely size of the shift before it hits. You can learn how to do it by following Google’s instructions for their report.
- Don’t panic-react to the February dip: Flag to your internal teams that a drop around that date is expected and explained, not a performance issue.
- Tighten creative and site performance, since BTR impressions depend on how fast creatives actually load and render:
- Optimize ad creative weight/assets.
- Review lazy-loading settings. We also suggest asking your AdTech partner to implement them in your setup and optimize them for maximizing ad revenue.
- Reduce unnecessary hops in the supply chain where possible, since more intermediaries mean slower rendering and fewer counted impressions.
- Align with your demand partners: Use this as an opportunity to compare discrepancy reports with advertisers and third-party measurement providers, since BTR is designed to shrink that gap.
What to Take Away From This
The switch from COD to BTR for measuring ad impressions is a measurement change, not a demand change, not a demand change, so it’s worth keeping an eye on your actual impression and revenue trends around the rollout to spot any shifts. It will start rolling out on February 17th, so there is plenty of time to audit your website and prepare for any potential impact.
Get in touch with our Publisher Success Managers if you’d like support navigating this change and optimizing your ad monetization setup for what’s ahead. They can give you insights on how to improve your rendering settings to optimize your impression count and maximize performance.
