Performance Max vs Search Keyword Cannibalization: What the Data Shows

Performance Max vs Search Keyword Cannibalization: What the Data Shows

Performance Max and Search campaigns frequently compete for the same search terms inside a single Google Ads account, and Search usually wins on the metrics that matter. Adalysis's analysis of over 3,300 non-retail PMax campaigns and roughly 1.2 million search terms found that 67% of PMax campaigns had overlap with Search on at least one term, and when both campaign types were eligible for the same query, Search delivered a higher conversion rate 84.18% of the time and a higher CTR 65% of the time, despite Performance Max often winning more of the impressions.

Key takeaways

1. 67% of Performance Max campaigns overlap with Search campaigns on at least one search term; the term-level overlap rate across all PMax search terms is 45%.
2. When both campaign types are eligible for the same query, Search wins on conversion rate 84.18% of the time and CTR 65% of the time.
3. PMax wins more impressions overall in 43% of eligible-term cases, rising to 61% when only overlapping campaigns are counted - meaning PMax can out-deliver Search even while converting worse.
4. Google's own "remove redundant keywords" recommendation in Google Ads actively encourages this cannibalization by removing the Search keywords that were protecting those terms.
5. Adding winning search terms as explicit exact-match keywords in Search, and layering negative keywords into PMax, are the two most effective protective measures.

The pattern this produces is subtle rather than dramatic: total account performance can look stable or even improving on a blended view, while the underlying mix quietly shifts toward more PMax-served impressions on terms that convert worse than they would have converted through Search. By the time this shows up as a declining blended conversion rate, the shift has usually been happening for months.

Search term overlap: when the same user query is eligible to trigger ads from both a Search campaign and a Performance Max campaign within the same account, and Google's auction-time logic decides which one actually serves.

Cannibalization: in this context, one of your own campaigns (PMax) winning impressions and spend on a term that would have converted better through a different one of your own campaigns (Search).

Why Performance Max wins impressions but Search wins conversions

The operational pain this creates for accounts running both campaign types: Performance Max's broader inventory access and machine-learning-driven delivery let it win a meaningful share of eligible auctions, but that delivery advantage does not translate into better outcomes on terms where a well-built Search campaign already has a strong, specific match.

A Search campaign with an exact-match keyword, tightly relevant ad copy, and a landing page built around that specific query has every Quality Score component - expected CTR, ad relevance, landing page experience - optimized for that exact term. Performance Max, by contrast, is matching the same query as one of many signals across a much broader asset group and audience signal set, without the same narrow, deliberate alignment. The auction priority rule reflects this: an exact-match keyword in Search generally takes priority in the auction over PMax for that term, but phrase and broad match are more contestable, depending on ad rank and whether PMax has built its own search theme around a similar term.

The counterintuitive trap: Google's own recommendation

The ICP problem this creates for accounts following Google's automated suggestions: Google Ads' "remove redundant keywords" recommendation, aimed at account hygiene, actively removes the Search keywords that were preventing PMax from winning those auctions - the opposite of what most teams assume a cleanup recommendation would do.

When an account has both a Search keyword and PMax eligible for the same term, Google may flag the Search keyword as "redundant" on the logic that PMax already covers it. Accepting that recommendation removes the exact-match protection keeping that term on the higher-converting Search campaign, and the term shifts toward PMax by default - with the CTR and conversion-rate gap documented above following it. Adalysis's study specifically advises ignoring this recommendation for any term where Search has been demonstrably outperforming PMax, since the recommendation optimizes for account tidiness, not for which campaign converts the term better.

Prooflytics

Stop stitching platform exports together

Every channel in one brief — plus the memory of what each one actually drove.

Start free trialSee pricing

14 days free · no credit card

How to protect Search from PMax cannibalization

Low - Monitor, no action yet. Pull the PMax search term report monthly and cross-reference it against your Search campaign's keyword list to identify overlapping terms. At this stage, the goal is visibility - knowing which terms are contested before deciding whether the overlap is actually hurting performance.

Mid - Reinforce Search on winning terms. For any overlapping term where Search has historically converted better, add it as an explicit exact-match keyword in Search if it is not already there, and improve Quality Score on that term specifically (relevance between keyword, ad copy, and landing page) to strengthen Search's auction position. This is the single highest-leverage fix and requires no changes to the PMax campaign at all.

High - Actively exclude from PMax. For terms where Search's performance advantage is clear and consistent, add them as negative keywords within the PMax campaign's own negative keyword list - now supporting up to 10,000 keywords per campaign as of 2026 - to stop PMax from competing for that specific term at all, rather than relying on auction priority alone.

Why this connects to the broader impression share picture

By the budget-versus-rank impression share framework, a term's impression share loss breaks down into two distinct causes: insufficient budget or insufficient Ad Rank. PMax-versus-Search cannibalization introduces a third dynamic specific to accounts running both campaign types - a term's Search impression share can decline not because Search's own budget or rank changed, but because a sibling PMax campaign is now winning a larger share of the same auctions. Diagnosing a Search impression share drop without checking for PMax overlap on the same terms risks misattributing the cause to a budget or Quality Score problem that does not actually exist - the real fix is the negative-keyword and explicit-keyword protection described above, not a bid or budget change.

Prooflytics surfaces search term data across both Search and PMax campaigns in the daily briefing, so an overlapping term's performance split between the two campaign types is visible in one view rather than requiring a manual cross-reference between two separate reports.

What to watch: leading signals for PMax cannibalization

• A Search campaign's converting keyword losing impression share with no corresponding budget or Quality Score change - check for PMax overlap on that exact term before assuming a rank or budget issue.
• Blended account conversion rate declining while blended impressions hold steady or grow - consistent with more volume shifting to the lower-converting campaign type (PMax) on shared terms.
• A "remove redundant keywords" recommendation appearing for a term Search has historically converted well - verify the term's actual Search-versus-PMax performance before accepting the recommendation.
• PMax search term reports showing repeat appearances of terms that already exist as exact-match Search keywords - a direct sign of the 45% term-level overlap rate showing up in your specific account.
• New PMax asset groups launched without a corresponding review of existing Search campaign keyword overlap - the overlap risk compounds every time a new PMax campaign or asset group goes live without this check.

Bottom line

• Expect meaningful overlap if you run both PMax and Search - 67% of PMax campaigns share at least one search term with a Search campaign in the same account.
• Search converts better on shared terms in the large majority of cases (84% conversion-rate win rate), even when PMax wins more impressions.
• Do not blindly accept Google's "remove redundant keywords" recommendation - it removes the exact-match protection keeping high-converting terms on Search.
• Reinforce Search with explicit exact-match keywords on winning terms, and add PMax negative keywords for terms Search should own outright.
• Book a walkthrough to see how Prooflytics surfaces search term performance across both Search and PMax campaigns in the same daily view.