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Performance Max brand cannibalization

playbook google ads updated 2026.04.30 5 min read
// contents · 9 sections
  1. What brand cannibalization in PMax actually is
  2. Why it happens by default
  3. How to detect it in your account
  4. How do I confirm PMax is cannibalizing my brand without guessing?
  5. Doesn't PMax already exclude branded traffic by default?
  6. Will excluding brand from PMax tank my PMax ROAS?
  7. How to fix it
  8. Related concepts
  9. Sources

PMax brand exclusions have been a UI checkbox since 2023 — if unticked, Performance Max eats your branded Search at lower CPCs and steals the conversion credit.

What brand cannibalization in PMax actually is

Brand cannibalization happens when a PMax campaign serves on queries containing your brand name that would otherwise go to your dedicated Search brand campaign. Smart Bidding inside PMax sees branded queries as the highest-converting intent on the account and bids aggressively — usually winning at a lower CPC than the brand Search campaign because Google's internal routing prefers PMax when both are eligible.

The result: brand Search impression share collapses, PMax shows a beautiful ROAS, and total branded spend rises while incremental revenue stays flat. You are paying Google to compete with yourself.

Why it happens by default

PMax launched without brand controls. Brand exclusions arrived as a closed beta in 2022, opened via support ticket through 2023, then became a self-serve UI checkbox on 2023-11-08:

"Brand exclusions in Performance Max give advertisers more control over which brand-related traffic their campaigns serve on, with separate exclusions for Search and Shopping inventory."
— Search Engine Land, 2023-11-08

Default state on every new PMax campaign: brand exclusions empty. Unless someone opens Campaign settings → Additional settings → Brand exclusions and attaches a brand list, PMax bids freely on your brand. Most accounts we audit never touched it.

How to detect it in your account

How do I confirm PMax is cannibalizing my brand without guessing?

Three signals together = confirmed cannibalization. (1) Open the PMax search terms report and filter for queries containing your brand — any volume here is cannibalization. (2) Compare brand Search impression share over the last 90 days vs the period before PMax launched — a >15% drop with stable brand demand is the smoking gun. (3) Check Search-slice spend in PMax channel-level on days you paused brand Search — it should not jump if PMax is incremental.

Doesn't PMax already exclude branded traffic by default?

No. The default is empty. Google added the PPC Land coverage of brand exclusions in 2023 explicitly because advertisers could not stop PMax from serving on brand. As of 2026 the default remains opt-out — you must add a brand list and tick the checkbox per campaign.

Will excluding brand from PMax tank my PMax ROAS?

Yes, on paper. Stripping branded conversions from PMax usually drops reported ROAS 20-40% because brand was the easiest conversion in the mix. The real question is incrementality: that brand revenue did not disappear — it shifted back to the brand Search campaign at a lower CPC. Total account ROAS rises even as PMax's standalone ROAS falls. This is why MER (account-level revenue / total ad spend) matters more than per-campaign ROAS for PMax decisions.

Whitead audit angle. In roughly 7 of 10 PMax accounts we audit, brand exclusions are empty and the channel-level tab shows 18-35% of PMax Search-slice spend hitting branded queries. The pattern is consistent: PMax shows a 6-9x ROAS that looks elite, brand Search impression share has quietly fallen from 92% to 60-70%, and the MER vs ROAS gap widens — campaign-reported ROAS climbs while the account's overall MER stays flat or declines. The fix takes 20 minutes: build a brand list under Tools → Shared library → Brand lists, attach it to every PMax campaign's brand exclusions for both Search and Shopping, and add brand variants as campaign-level negatives as belt-and-braces. Within 14 days, brand Search IS recovers, PMax ROAS drops to its true incremental level, and the same total revenue costs noticeably less. The "lost" PMax ROAS was always your brand campaign's revenue wearing a PMax wig.

How to fix it

  1. Build a brand list (Tools → Shared library → Brand lists) including your brand, common misspellings, and product line names. Google matches against this list across languages.
  2. In each PMax campaign open Campaign settings → Additional settings → Brand exclusions and attach the list. Tick both "Search" and "Shopping" — they are separate toggles.
  3. Add the same brand variants as campaign-level negative keywords on the PMax campaign (you have 10,000 slots — use 50). Brand exclusions cover what Google identifies as branded; negatives cover what Google misses.
  4. Verify in incognito: search your brand 24-48 hours after the change. PMax should not serve. If it does, audit the brand list for missing variants.
  5. Re-baseline: screenshot brand Search impression share, PMax channel-level spend split, and account MER on the change date. Compare at day 14 and day 30.
  • Performance Max — the campaign type, including the 2025 transparency overhaul that made this diagnosable.
  • Negative Keywords — the 10,000-per-campaign cap that lets you belt-and-brace brand exclusions.
  • Performance Max not converting — related diagnostic when PMax under-delivers despite high reported ROAS.

Sources

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