A quick primer
Google Ads has a purpose-built tool for this exact question: the channel performance report. It helps you understand how a PMax campaign is delivering results across Google's full range of channels and inventory, with a campaign-level summary plus a breakdown of how each channel contributes to your goals. The report has three parts. A Performance summary covers campaign-level figures (actual ROAS or CPA, target ROAS or CPA, interactions, conversions, cost). A Channels-to-Goals chart shows how each channel supports your goals. And the channel distribution table gives you the most detail: impressions, clicks, interactions, conversions, conversion value, cost, Results, and Results value, broken out row by row.
The "Channel" segmentation in this report officially covers Search, Display, YouTube, Discover, Maps, Gmail, and Search partners, exactly the list you need for this question. A separate slice, "Ads using product data," covers Shopping ads pulling from your Merchant Center feed across Search, YouTube Search, Maps, and Search partners, plus dynamic remarketing on Display. So the Shopping side of PMax shows up as an extra layer on top of the regular channels, not as a channel of its own.
A time series chart inside the same report is useful for pinpointing exactly when a shift happened: it helps identify where channel mix changed, for example right after adding a video asset or changing your goals or bid strategy targets.
What to check before you touch anything
- Are you looking at the channel distribution table itself, not just the top summary. The channel-level breakdown lives in the table, not in the Performance summary.
- Have you added the "Ads using product data" segment. Without it, the Shopping side of PMax stays folded into Search, Display, and YouTube instead of showing up on its own.
- What date range you're looking at. Full detail in this report is available for dates after June 6, 2025; earlier periods may not have the same granularity.
- Does the spend growth on a specific channel line up with the date you added new assets (video especially) or changed your goals or bid strategy. The time series chart shows this directly.
- Are you filtering by "Conversions" or "Results." The first shows conversions your campaign is optimizing toward; the second shows conversions across every goal in the account, including ones you're not optimizing for. They're different numbers.
Possible approaches
- Start with the channel distribution table, sorted by Cost, to see right away which channel is driving the bulk of spend and how that compares to where things stood at the start of the period.
- Add the "Ads using product data" segment if the business runs a Merchant Center feed. This separates Shopping-driven spend growth from the growth of the underlying channel format itself.
- Use the time series chart for a specific channel to find the exact date spend started rising, then cross-reference that with your account's change history (new assets, a bid strategy switch, a goal change).
- If growing spend on a channel comes with an "Eligible" status and no warnings in the Status column, that most likely means PMax is simply shifting budget toward the channel with the higher predicted ROI at that moment, not a technical issue.
- Check this report regularly, not just once. Channel mix can shift naturally with seasonal demand, not only in response to changes you make in the campaign.