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Google Ad Manager Is Changing How It Counts Impressions — Here's What Publishers Need to Know
The Aditude Team
On September 1, 2026, Google sent a mandatory notice to Ad Manager publishers announcing a change to how display ad impressions are counted. Starting February 17, 2027, Google Ad Manager will shift from Count-on-Download (COD) to Begin-to-Render (BTR) methodology across all display inventory, web, mobile web, and CTV banner.
If you haven't had a chance to dig into what this actually means for your numbers, this post breaks it down.
What's Changing
Right now, Google Ad Manager counts a display impression the moment the ad server responds to a request and the creative asset begins downloading to a user's device. That download could stall. The user could close the tab. The ad might never actually appear on screen — and yet, it counts as an impression under the current methodology.
Beginning February 17, 2027, an impression will only be counted once the ad creative has successfully loaded and begun rendering on the user's device. This is the Begin-to-Render (BTR) methodology, which is already the standard used by the IAB and Media Rating Council (MRC), and the methodology Google already applies to native, app, and video inventory. Display ads are simply being brought into alignment.
Why Google Is Making This Move
The short answer: consistency. Buy-side platforms and third-party measurement vendors have largely operated on BTR for some time. Publishers using GAM's COD counting have had to account for discrepancies between what their ad server reports and what demand partners report, often by buffering campaign delivery. BTR removes that mismatch.
Campaign Manager 360 and Display & Video 360 are making the same shift in February 2027. The change is happening across the Google stack simultaneously, which signals this is a deliberate ecosystem-wide standardization rather than an isolated update.
What Publishers Should Expect
Your reported impression numbers will go down. That's the headline.
Impressions that began downloading but never rendered, because a user navigated away, had a slow connection, or Chrome's heavy ad intervention blocked the ad, will no longer be counted. The actual ads being seen by real users have not changed. Your real audience and real revenue have not changed. What changes is the denominator used to calculate metrics like RPM and eCPM.
The practical effect: RPM and eCPM will likely increase as fewer lower-quality impressions are included in the count, even if actual earnings stay flat. Treat that as a metric normalization, not a performance improvement.
Google has confirmed that no action is required from publishers. The switch applies automatically on February 17, 2027.
How to Estimate Your Impact Before the Deadline
Publishers who want to understand the gap between their current COD counts and future BTR counts can run a comparison report directly in Ad Manager today. Google has made BTR impression data available in reporting now, using a historical start date of August 12, 2026 or later.
To set it up:
Go to Reporting in your Google Ad Manager account.
Create a new Interactive Report.
Add the metric "Ad server impressions" (your current COD count) alongside "Ad server begin to render impressions" (the future BTR count).
Add these dimensions for a meaningful breakdown: Demand channel, Inventory format, Inventory type (expanded), Device category.
Set the date range to start on or after August 12, 2026.
The delta between those two metrics is the impression volume that will stop being counted after the transition. Review it by device and format to understand where the largest discrepancies sit, a slow mobile template can show a very different gap from a fast desktop article page, even when the account-level totals look stable.
Google has also indicated that additional BTR metrics for Ad Exchange and yield group impressions will be added to reporting in the near future.
A Note on Creative and Lazy Loading Settings
Two technical factors can influence how your BTR impression counts land.
Creative weight: Ad creatives that consume excessive network or CPU resources risk being blocked by Chrome's heavy ad criteria before they render, which means no BTR impression is recorded. Google has recommended reviewing creative asset optimization ahead of the transition.
Lazy loading and lazy rendering configurations: These settings directly affect when creative assets begin rendering in the browser, which is now the moment impressions are counted. If you're using renderMarginPercent or fetchMarginPercent settings in GPT, increasing those values causes assets to render earlier in the page experience, which could improve BTR counts. That said, it also increases resource demands on your network and end users' devices, so weigh that trade-off against your site performance priorities before making adjustments. Google's GPT lazy loading documentation covers those parameters in detail.
The Bigger Picture
BTR is already how video, native, and in-app impressions are counted inside GAM. This update brings display in line with the rest of the platform, and with how buyers have been measuring for years. For publishers, that alignment reduces the friction of reconciling discrepancies with demand partners, which has real operational value even if it doesn't show up immediately as a revenue line item.
The February 2027 deadline gives publishers roughly five months to pull the comparison report, understand their gap, and make any creative or configuration adjustments. That's enough runway to act, but not enough to ignore.
Have questions about how this change intersects with your ad stack setup? Reach out to the Aditude team.
