Performance Max Brand Cannibalisation Check
Performance Max blends brand and non-brand demand into one ROAS figure. Estimate how much PMax spend is re-buying demand you already own, and how to control it.
Performance Max brand cannibalisation, how to prove it, not guess at it
Performance Max cannibalises brand search when it serves ads to users who would have clicked your organic or brand-campaign result anyway. It shows up as rising PMax conversions alongside falling brand-campaign impression share and flat total revenue, and it is diagnosed with brand exclusions and search-term data, not intuition.
The mechanism is simple. Performance Max is granted access to the search inventory, and because brand queries convert at the highest rate of any traffic in the account, the campaign's automation naturally gravitates toward them. Reported performance improves, cost-per-acquisition falls, and the dashboard looks excellent, while the incremental revenue the campaign is actually generating stays flat, because those customers were already arriving.
Diagnosis needs evidence. Apply brand exclusions to the Performance Max campaign, then compare total account revenue, brand-campaign impression share and organic brand click volume before and after. If Performance Max conversions fall while total conversions hold steady, the campaign was harvesting existing demand. If total conversions drop with it, the campaign was genuinely incremental and the exclusions should be reconsidered.
The correction is structural rather than tactical: keep a dedicated brand search campaign to control brand messaging and cost, apply brand exclusions to Performance Max so it works prospecting inventory, and judge the campaign on new-customer acquisition and total account revenue rather than its own attributed conversions. Where the platform allows, an incrementality or geo holdout test is the strongest evidence available.
Frequently asked questions
What is Performance Max brand cannibalisation?
It occurs when a Performance Max campaign claims conversions from users searching your brand name, traffic that would have converted through organic results or a brand search campaign anyway, inflating the campaign's reported performance without adding revenue.
How do I test whether PMax is cannibalising brand traffic?
Apply brand exclusions to the campaign and compare total account conversions and revenue, brand-campaign impression share and organic brand clicks across matched periods. Flat totals with falling PMax conversions indicate cannibalisation.
Should I always exclude brand terms from Performance Max?
In most established accounts with existing brand demand, yes, it forces the campaign onto prospecting inventory. Newer brands with negligible brand search volume have less to protect and may see little difference either way.
Which metrics reveal the problem fastest?
Brand-campaign impression share and average CPC, organic branded click volume in Search Console, new versus returning customer share, and total account revenue, not the Performance Max conversion column in isolation.
Does a brand search campaign still earn its place alongside PMax?
Usually. It gives control over brand messaging, protects against competitor bidding, and provides the clean baseline you need to measure whether Performance Max is genuinely incremental.