You can run product campaigns for years without ever looking at Merchant Center, until the day Google sales suddenly drop and several hundred disapproved products are waiting in the diagnostics. This guide explains why a shop needs Merchant Center, how to read its diagnostics, what supplementary feeds are and how to fill them with data that Google cannot calculate on its own.
Basics
What Google Merchant Center is and why you need it
Merchant Center is often confused with the advertising panel. Its role is different:
Definition
Google Merchant Center is a free account in which a shop stores and controls its product data for the entire Google ecosystem. The feed uploaded to Merchant Center is used by paid product campaigns and Performance Max in Google Ads, as well as by free product listings in search results. It is also where Google assesses every product: it either approves it for display or disapproves it with a stated reason.
In practice, Merchant Center answers three questions. First: what Google knows about your products (feed data). Second: which products can be shown at all (statuses and diagnostics). Third: how products perform in Google (impressions and clicks, including in free results, which are not visible in Google Ads).
On Google’s side, Merchant Center acts as quality control: a product it does not accept will not appear in campaigns or in free results, regardless of budget. The basics of the feed itself are covered in a separate guide: the product feed and splitting the catalogue.
Diagnostics
Product statuses: how Merchant Center assesses the feed
On any given day, every product in Merchant Center has one of three statuses. Approved products are shown normally. Disapproved products are not shown anywhere until the problem is resolved. Pending products are awaiting processing. This is what a daily snapshot looks like for an example sports shop (illustrative data):
Diagnostics · catalogue of 6,240 products · daily snapshot
The percentages show the number of products, not their weight in revenue. A disapproved 5% of the catalogue can mean 1% of revenue or 20%, depending on whether long-tail products or bestsellers have dropped out. That is why statuses should be read together with sales data.
Where do disapprovals come from? Usually from a mismatch between the feed and the shop: a price in the file that differs from the page, an unavailable product, missing GTIN identifiers, an image with promotional text. Merchant Center gives a reason for each product. The problem is that the list can run to hundreds of items, and without linking it to sales data it is unclear where to start.
Real risk
A disapproved bestseller stops selling silently. The campaign keeps running and the budget is spent on the rest of the catalogue, so nothing raises an alarm at account level. The drop only shows up in sales, often weeks later, and the cause was a single price mismatch detected by Google’s crawler.
A product disapproved in Merchant Center does not lose the auction: it never enters it.
Mechanics
Supplementary feed: extra data without changing the shop
A supplementary feed (also called an additional or complementary feed) is a second data source in Merchant Center that does not create products but adds or overrides selected attributes of products from the primary feed. The two are matched on a single key: the id identifier. The mechanism works like this:
Primary feed · from the shop
Supplemental feed · sheet
Record in Merchant Center
Why go to all this trouble? The primary feed is generated by the shop platform, and every change to it means interfering with the integration: a ticket to IT, a change to the export template, the risk of breaking the whole thing. A supplemental feed avoids this problem: the shop supplies what it knows (prices, stock levels, descriptions), and the analytics layer adds what the shop does not know: custom labels calculated from margin, sales velocity or stock levels. These are exactly the labels on which catalogue segmentation in campaigns relies.
Key takeaway
Division of roles: the shop describes the product, analytics describes the strategy. Prices, stock levels and descriptions stay in the primary feed, because they must match the website. Labels, title corrections and strategic data come in through the supplemental feed, without touching the shop integration and without involving IT.
Automation
DataOrganizer labels via Google Sheets
Merchant Center has been able to read Google Sheets as a supplemental feed for years, and this is the simplest way to get labels calculated from data into campaigns without uploading files manually. DataOrganizer completes this loop with a Google Sheets add-on: the sheet fills itself with values from the shop’s connected data.
| A | B | C | |
|---|---|---|---|
| 1 | id | custom_label_0 | custom_label_1 |
| 2 | RUN-0942-42 | high-margin | rotation-a |
| 3 | SHO-1180-XL | low-margin | rotation-c |
| 4 | BUT-2214-44 | high-margin | new |
| … | 6,240 rows · values refreshed together with the data | ||
The whole flow, from data to campaigns, consists of four steps:
The add-on fills the sheet
In Google Sheets, the DataOrganizer add-on pulls the
idcolumn from the shop’s connected data, together with label values calculated from margin, sales velocity, stock levels or price position, for the entire catalogue at once.The sheet becomes a supplemental feed
In Merchant Center, you add a supplemental data source and point it to this sheet. You assign it to the primary feed; from then on, the sheet’s columns are attached to products by
id.A schedule keeps the data up to date
Merchant Center fetches the sheet on a schedule, and the values in the sheet refresh together with DataOrganizer data. The “low-stock” label disappears on its own once a delivery reaches the warehouse.
Campaigns use the labels
From the next feed processing onwards, the labels are visible in Google Ads: product groups in Performance Max and Shopping campaigns can be split by the values from the sheet.
A practical note: the sheet is also a natural checkpoint. Before the labels go to campaigns, every value is visible in black and white, and you can correct it manually or add your own column. Automation does not take away manual control; it only removes the copying.
Data
What DataOrganizer pulls from Merchant Center
The connection works both ways. DataOrganizer does not only feed labels into Merchant Center; every day it also pulls data from it that is not available anywhere else. The loop closes in four steps:
Two datasets flow from Merchant Center into the connected database:
| Dataset | What it contains | What it is for |
|---|---|---|
| Product statuses (daily snapshot) | approved / disapproved / pending status and the number of issues for each product | feed quality monitoring and change history: you can see on which day products dropped out |
| Product performance | impressions, clicks and conversions per product, separately for Shopping campaigns and free listings | product visibility in Google, including free traffic not visible in Google Ads |
Only in a connected database does this data become truly useful: statuses can be compared with sales (which disapproved products really hurt), and performance with margin (which products Google readily shows, even though they should not receive budget). A single question to the AI assistant settles an issue that would take three exports to answer manually:
Disapproved: 316 products (5.1% of the catalogue). Reasons and traffic in the 30 days before disapproval:
| Disapproval reason | Products | Impressions before |
|---|---|---|
| Price mismatch with website | 128 | 21,320 |
| Missing GTIN or brand | 94 | 3,480 |
| Image issues | 61 | 7,660 |
| Policy violations | 33 | 1,280 |
74 of the 316 products (23%) were still getting impressions in the last month; these are the ones costing the most. The quickest win: price mismatches, as they affect 128 products, including most of those with traffic. I can generate a list in a sheet for the person who manages the feed.
Context
How Merchant Center data complements sales and costs
Shop data shows what sold. Advertising data shows what it cost to reach the buyer. Between them lies a gap: nobody knows what Google actually displayed, which products it refused to serve and what traffic arrived for free. Merchant Center fills exactly this gap:
| Data layer | Source | Question it answers |
|---|---|---|
| Sales | shop orders | what actually sold and at what price |
| Costs | advertising platforms | what it cost to reach the customer |
| Product visibility | Merchant Center | what Google showed and what it refused before any click happened |
In a connected e-commerce data model, Merchant Center contributes three things that are not available anywhere else. Feed health: the daily status history shows when and which products dropped out of serving; this is often the missing piece when explaining sales declines. Free product traffic: free product listings live outside Google Ads, so without Merchant Center this channel is invisible. Per-product visibility: impressions and clicks at the level of a single SKU complete a picture in which costs from other platforms stop at campaign level.
Methodological note: conversions reported by Merchant Center and Google Ads are counted according to Google’s rules, so they are not the same as shop orders. Paid orders always remain the reference point; the guide to automated e-commerce analytics explains why.
Where the advantage lies
On its own, Merchant Center is just a list of statuses. The value appears where data meets: statuses × sales show which disapprovals hurt; performance × margin shows what to promote; labels × spreadsheet close the loop back to campaigns. DataOrganizer maintains this connection automatically, on data refreshed every day.
FAQ
Frequently asked questions about Google Merchant Center
Is Google Merchant Center free?
Yes. The account is free, as are free product listings, which let products appear in Google results without paying for clicks. Costs only arise when you run paid product campaigns in Google Ads from the same account.
Why does Merchant Center disapprove products?
Most often because of a price or availability mismatch between the feed and the product page, missing identifiers (GTIN, brand), image problems (watermarks, promotional text) and policy violations. Every disapproval has its reason listed in diagnostics. A disapproved product is not served in campaigns or in free listings until the problem is fixed.
Can a supplementary feed override prices?
Technically it can override almost any attribute, but price and availability must match the product page, otherwise products will be disapproved. That is why prices and stock are best left to the primary feed from the shop, with the supplemental feed used for data the shop does not have: custom labels, title corrections, additional attributes.
How do I connect a Google Sheet as a supplementary feed?
In Merchant Center, go to data sources and add a supplemental data source, choosing Google Sheets. The sheet must have an id column matching the primary feed and columns for the attributes to add (e.g. custom_label_0). After linking it to the primary feed, set a fetch schedule; from then on the values refresh without your involvement.
What do free product listings in Google offer?
These are free product impressions in Google results, including the Shopping tab; a valid feed in Merchant Center is all it takes. This traffic is not visible in Google Ads because it is not a campaign. It is worth tracking separately: it shows which products attract attention organically before you spend advertising budget on them.
Cheat sheet for the whole guide
Three rules for working with Merchant Center
1. A disapproved product disappears from Google entirely: it does not enter auctions and does not appear in free listings. Statuses should be read daily and always alongside sales, because 5% of the catalogue disapproved can mean 1% of revenue or 20%.
2. A supplemental feed separates strategy from integration. The shop maintains prices and stock in the primary feed, while labels and analytical data arrive via a separate source matched by id, for example a Google Sheet that the DataOrganizer plugin fills with values calculated from margin, turnover and stock levels.
3. The loop runs both ways. From Merchant Center, it is worth pulling product statuses and performance (including free listings) every day, and sending labels back. Only when this data meets sales and costs does it show which disapprovals hurt and what truly deserves budget.
DataOrganizer · Merchant Center under control
Connect your shop and Merchant Center: product statuses and performance meet sales and margin, and labels return to campaigns via Google Sheets. Demo account available instantly; you only pay for connected sources.