Google Ads for ecommerce: Search, Shopping, Performance Max and Demand Gen
This page is about the technology and how to judge it. For the channel decision as a whole, read our paid media strategy for ecommerce.
What does it do?
Google's documentation describes Performance Max as a goal-based campaign type that reaches all Google Ads inventory, including Search, YouTube, Display, Discover, Gmail and Maps, from one campaign. Your assets, data feeds and bidding goals are combined with Google AI, which optimises delivery towards those goals1. Google positions it as a complement to keyword-based Search campaigns1. For a shop, the data feed is the product feed.
That feed lives in Google Merchant Center, the account where you upload and manage your product data. After the first mention we call it Merchant Center. See what is Google Merchant Center.
Demand Gen combines image and video ads across YouTube, including Shorts, Discover, Gmail, Maps and the Display network, and Google says it can use product feeds2.
Search ads still matter. They answer a question someone is already typing. How bids are set depends on the bid strategy you pick: from manual bids to automated targets such as target ROAS.
Why do e-commerce brands use it?
Because people search for products on Google. Our view: that makes it the channel with the most obvious intent, and for most shops the first one worth running.
It also scales from a handful of products to a whole catalogue, if the feed is clean.
How do we implement it?
Fix tracking first
Check that conversions are recorded properly, with an order ID. Bidding learns from the numbers you give it.
Clean the feed
Titles, prices and availability in Merchant Center should match what the landing page shows.
Set the structure
Decide what Performance Max may cover, which controls you use and what stays in separate campaigns. Judge Demand Gen as discovery.
Question the credit
Plan a brand search test to see how much traffic you would have kept anyway. Read platform ROAS as credit to ads, not profit.
When should you not use it?
Do not scale it if your tracking is broken. Fix that first.
Do not hand it everything if you cannot read what it did. Our view: a channel you cannot question is a risk, not a plan.
Do not run Demand Gen as a search replacement. Our view: it is built around visual surfaces, so judge it as discovery, not as intent capture.
What does it cost in effort?
No figures. The effort is:
- Feed. Keep product data accurate and complete in Merchant Center. Our view: titles, prices and availability should match what the landing page shows.
- Tracking. Conversions must be recorded properly, or bidding learns from bad numbers.
- Structure. Decide what Performance Max may cover and what you keep in separate campaigns.
- Controls. Google lists search themes, negative keywords and brand exclusions among the Performance Max controls1. Decide which ones you use, and why.
- Reading. Someone has to interpret what the reports leave out.
Pitfalls
Taking credit for existing demand
Our view: brand search and Performance Max can claim sales that cannibalisation makes look incremental. Brand exclusions are one control for this1. A brand search test can show how much of that traffic you would have kept anyway.
The black box
A Shopping tool vendor has described Performance Max reporting as limited3. Reporting changes over time, so check what your account shows today. Plan to question it, not just read it.
A messy feed
Our view: if similar products carry near-identical titles, the ads cannot tell them apart. Product data quality caps what the ads can do.
Ignoring returns
Google Ads lets you adjust recorded conversions after the fact: restate their value or retract them completely. This needs conversions tracked with an order ID. Google says automated bidding reads adjustments made within 7 days of the conversion being recorded, and adjustments are possible up to 54 days4. Our view: if returns are meaningful, upload them quickly so bidding does not chase sales that came back.
Chasing impression share
It is the share of eligible impressions your ads got. It says how often you showed, not whether showing paid.
Judging by platform ROAS
It credits ads, not profit.
Our take: Core
In our view, Google Ads is Core. That is our rating, not a market fact.
Our reasoning: for most ecommerce brands it is part of the foundation, not an experiment. But "Core" does not mean "trust the dashboard". A Google Shopping technology vendor wrote in 2022 that Performance Max offers only limited reporting, which makes it a black box for many advertisers3. Google's own list of controls includes brand exclusions1. That tells you where the risk is: credit for demand that already existed.
For ZFD: We start with the account's conversion tracking and the feed, then look at where credit goes.
FAQ
What is Performance Max?
Google describes it as a goal-based campaign type that reaches all Google Ads inventory, including Search and YouTube, from one campaign1.
What is the difference between Performance Max and Demand Gen?
Can I stop Performance Max bidding on my brand name?
Google lists brand exclusions among the Performance Max controls1. Whether that fits your account is worth checking.
Do I need a product feed?
For Shopping-style ads, yes. Demand Gen can use one too2.
Can I adjust conversions for returns?
Yes. Google lets you restate a conversion's value or retract it, if your conversions are tracked with an order ID4. Whether that suits your set-up depends on your shop data.
Sources
- About Performance Max campaigns (Google Ads Help)Primary source
- About Demand Gen campaigns (Google Ads Help)Primary source
- Performance Max for retail: your questions answered (Smarter Ecommerce)Blog or media
- How to adjust your conversions (Google Ads Help)Primary source
Let’s find what’s actually working.
Next step. Not sure where your Google Ads credit is going? Talk to us about your budget decision. See also our paid media service.