Google Ads Performance Max - trustworthy or not?

Performance Max is Google's most controversial campaign type. Google presents it as the future of advertising: one campaign that automatically optimises across all Google channels. Critics call it a black box that gives Google more control over your budget and trades transparency for convenience. Both have a point - depending on how you use it.

What is Performance Max?

Performance Max (PMax) is a campaign type that shows ads across all Google channels at once: Search, Display, YouTube, Shopping, Google Maps and Gmail. One campaign, one budget, Google decides where and to whom.

PMax replaced Smart Shopping and Local campaigns in 2022. The difference from classic campaigns: you give Google assets (copy, images, videos) and a conversion goal, and the algorithm handles the rest. You have little control over placements, bids or audiences, which is both its strength and its risk.

When does Performance Max work well?

PMax performs best when the conditions are right:

• Large product catalogues: PMax combines well with an optimised Shopping feed and can quickly find the best-converting combinations across hundreds of products
• Sufficient conversion data: the algorithm needs at least 30–50 conversions per month to optimise meaningfully - more is better
• Clear conversion values: if Google knows which conversions are worth more, it optimises for value instead of volume
• Strong asset library: PMax combines copy, images and video automatically - the more variation you supply, the better the system can test

The risks nobody tells you about

PMax has three structural risks that come up in most account analyses:

• Brand cannibalisation: PMax bids on your own brand name by default. So you're paying for traffic you'd otherwise have gotten organically. The result looks good in the reporting, but you're effectively pulling money from your own pocket
• Margin-blind optimisation: Google optimises for revenue or conversions, not margin per product. A cheap product with a high conversion rate beats a more expensive product with a better margin, unless you actively correct for it with conversion value rules
• Limited transparency: you can't see which search terms PMax has shown on in Search. That makes adjusting harder - there are still levers to pull, but they're subtler than in classic campaigns and require knowing where to look

How do you use Performance Max responsibly?

PMax isn't inherently bad - it's dangerous without the right guardrails. These are the settings that make the difference:

• Brand exclusion: exclude your brand name as a search term so PMax doesn't compete with your own brand keyword campaign
• Conversion value rules: assign a higher value to more expensive or higher-margin products, so the algorithm optimises for actual return
• Combine with Search: PMax has no say over specific keywords in classic Search campaigns. Keep those separate for your strategic keywords
• Test asset groups: create multiple asset groups per product category so you can see which combinations work

The honest conclusion

Performance Max is a powerful tool in the right hands, and a budget leak in the wrong ones. Most advertisers running PMax without brand exclusion and conversion value rules are unknowingly paying for brand traffic and low-margin products while the reporting looks perfectly fine.

PMax isn't handing over all the reins - it's letting go of the ropes and letting Google do the work. There's still control, but it's subtler than in classic campaigns. You need to know which levers you're pulling and when. Use PMax as part of a broader account structure, not a replacement for it. And don't be seduced by a good-looking ROAS in the dashboard if you don't know where it's coming from.