You’ve built a Performance Max campaign and attached a feed, and now you’re staring at the results wondering which part is doing what. Is Merchant Center running the ads? Is Google Ads? It’s a fair question, because the two tools overlap in ways that aren’t obvious. Here’s the relationship for Google Merchant Center and Performance Max in plain terms.
Merchant Center stores your product data, and Performance Max uses that data as the starting point for its ads and decides where and when they show. Google describes it this way: “Your product feed will be used as a starting point to create and show your ads”[5]. You manage products in one place and campaign settings in the other.
What each side actually does
Think of Merchant Center as the stockroom and Performance Max as the shop window team. The stockroom knows every product: title, price, availability, images, description. The window team decides which products go on display, in front of whom and how much to spend doing it.
That split matters when something goes wrong. If a product isn’t showing because it’s disapproved or missing a price, that’s a Merchant Center problem. If it’s approved but gets almost no spend, that’s a campaign question: budget, bidding, how your asset groups are set up. Diagnose which side owns the problem before you change anything.
We compare the two platforms at https://oxfordimpulse.com/google-merchant-center-vs-google-ads-difference/ and explain the feed itself at https://oxfordimpulse.com/beginners-guide-google-merchant-center-feed/ if you need either.
How the link works in Performance Max
Before you start, your Google Ads account needs to be linked to your Merchant Center account. Once the campaign exists you can’t swap the Merchant Center account on it, so check you’ve picked the right one before you save[1]. If you haven’t made the connection yet, https://oxfordimpulse.com/how-to-link-google-merchant-center-to-google-ads/ walks through it.
The campaign flow in Google Ads goes like this: Create, then Campaign, then choose an objective such as Sales, then select Performance Max. At that point you select your Merchant Center account and, if it applies to you, the country or feed label[1]. If you sell in more than one market, check that choice carefully.
Google also offers options at creation: a campaign built with products from Merchant Center, or one aimed at online sales or lead generation goals without that product focus[3]. If you want your products in your ads, you want the first.
Watch out
Google Ads updated how bidding strategies are labelled from June 2026[1]. If the names in your account don’t match older guides or screenshots, check the current help pages rather than assuming a setting has disappeared.
What the feed drives automatically
Once a feed is attached, assets are automatically generated from it[2]. Assets are the building blocks of an ad: headlines, descriptions, images. Google’s default is to auto-generate them, and you can launch without supplying your own, though Google recommends adding them[2].
Listing groups are also required. A listing group is the set of products an asset group will promote, and it defaults to all products in the Merchant Center account[2]. That default is worth checking. If your catalogue includes low-margin items, accessories or clearance stock, “everything” probably isn’t what you want your budget behind.
This is the point where feed quality turns into ad quality. The ad starts from your product data[5], so a weak title or a blurry image can show up in the ad itself.
What you control
Performance Max is automated, but you still have some control. Google’s own optimisation guidance points to three areas you can work on[5].
Asset groups and product targeting
You can target different products with each asset group[5]. Say you sell both running shoes and rucksacks. Separate asset groups let each have its own creative and its own product selection, rather than one blended group trying to speak to everyone. The trade-off: more groups mean more setup and more to monitor. Start with the two or three categories that matter most to your revenue.
Custom labels
Custom labels are fields you add to your feed to tag products your own way, for example “bestseller”, “high margin” or “seasonal”. Google recommends using them to signal high-priority products[5]. Tag your products in the feed first, then use the labels to tell the system which ones matter most.
Data quality
Google’s guidance is to upload rich descriptions and images, update price and availability when they change and use the Product issues column to find missing attributes[5]. Check the Product issues column[5] and fix what’s flagged, starting with your best sellers.
Performance Max or Standard Shopping?
Standard Shopping campaigns are still offered. When you create a campaign tied to a Merchant Center feed, you can create a Performance Max campaign or proceed with a Shopping campaign[4]. The choice depends on how much automation you’re comfortable with and how much control you want over the setup. Neither is simply better, so judge them against your own goals and your own data.
Common ways this goes wrong
- Wrong account linked. You can’t change it after the campaign is created[1], so check before you save.
- Default listing group left alone. All products in the account get promoted[2], including ones you’d never choose to push.
- Stale feed data. Price or availability changes in your shop but not in Merchant Center. Google’s guidance is to update them when they change[5].
- Thin product titles and descriptions. Assets are generated from your feed[2], so thin product data gives them less to work with.
What to check this week
Check the Product issues column[5]. Fix the top issue on your best sellers. Then open your Performance Max campaign, look at the listing group for each asset group and confirm it covers the products you want and nothing else.
Merchant Center holds the products and Performance Max decides how they are shown, so fixes start with working out which side owns the problem. The Merchant Center hub at https://oxfordimpulse.com/google-merchant-center/ is the place to go next for the wider picture.
FAQs
Do you need Merchant Center to run Performance Max?
No, but you need it for product-led campaigns. Google offers a Performance Max option for online sales or lead generation goals as well as one built with products from Merchant Center[3]. If you sell products and want them in your ads, use the feed.
How do you link Merchant Center to Performance Max?
Make sure your Google Ads and Merchant Center accounts are linked first. Then create a campaign, choose an objective such as Sales, pick Performance Max and select your Merchant Center account[1]. You can’t change that account once the campaign exists.
Can you change the Merchant Center account on a campaign later?
No. Google states you can’t change the Merchant Center account after the campaign is created[1]. Check the account before you save.
Does Performance Max create ads from your product feed?
Yes. With a feed attached, assets are automatically generated from it[2]. Google also recommends adding your own assets.
Can you launch Performance Max without your own creative?
Yes. Google’s default is to auto-generate assets, so you can launch without your own[2]. Google still recommends adding them, so treat that as a start rather than a finished setup.
Which products does Performance Max promote by default?
Listing groups are required and default to all products in the Merchant Center account[2]. Narrow this if you want budget behind specific categories or margins.
Can you choose which products appear in each asset group?
Yes. You can target different products with each asset group[5]. This lets you give separate product sets their own creative.
What are custom labels used for?
They’re feed fields you define yourself to tag products, such as bestsellers or high-margin items. Google recommends using custom labels to signal high-priority products[5].
Is Standard Shopping still available?
Yes. When you create a campaign with a feed, you can create a Performance Max campaign or proceed with a Shopping campaign[4]. Choose based on how much control you want.
How do you find problems in your product feed?
Use the Product issues column to find missing attributes[5]. Also keep price and availability up to date, and upload rich descriptions and images.
Sources
- Google Ads Help: Step 1: Create your campaign and choose a goal support.google.com
- Google Ads Help: Step 4: Set up your asset group and assets support.google.com
- Google Ads Help: Options to create your Performance Max campaign support.google.com
- Google Ads Help: Create a Shopping campaign support.google.com
- Google Ads Help: Optimization tips for Performance Max campaigns with a Google Merchant Center feed support.google.com
