Guide · FifteenFold
Merchant Center feed optimisation: titles, GTINs, attributes and product data
Product data sits behind your store, Google Shopping, Performance Max and marketplaces. When it is weak, every channel gets a poorer version of your catalogue, and more ad spend will not fix it.
Quick answer: product data is the connective tissue of ecommerce. If titles, identifiers, variants, categories, availability or attributes are wrong, the same bad information appears in your store, your ads and your marketplaces at once. Fix it at the source before scaling spend.
Google can only work with what you send
If a title is vague, a GTIN is missing, availability is stale or product type is poorly mapped, Google has less reliable information to match and present the item. “Feed optimisation” simply means improving that information and the rules around it.
The feed is part of the marketing system
Dealing with feed errors or missing products? Request free Merchant Center triage
Feeds are often treated as plumbing that moves catalogue data into Merchant Center. In practice the feed decides what each channel knows about your products, which shapes eligibility, matching, segmentation and reporting.
What to check first
- Titles that identify the exact item and variant, with the attributes people search for.
- Identifiers: brand, GTIN, MPN and identifier_exists set correctly. See the GTIN guide.
- Categories: product type and Google product category mapped consistently.
- Attributes: colour, size, material, gender, age group and category-specific fields.
- Price and availability matching the landing page. See mismatch guide.
- Images that show the exact offer, without overlays or placeholder graphics.
- Promotions and shipping aligned with what the website actually charges.
- Out-of-stock and discontinued products handled so they do not waste budget or trigger errors.
Before scaling Performance Max
Performance Max can find demand, but it depends on the product signals underneath. Vague titles, missing attributes, unclear variants and recurring Merchant Center warnings give the campaign poor inputs. Clean the fields that affect your most important products first, then scale.
Customers feel data problems too
Wrong colour names, duplicated variants, missing dimensions or inconsistent condition labels create friction on the site itself. Good product data is not back-office housekeeping; it shapes the buying experience.
Fix the source, not just the feed
Feed rules can patch symptoms, but the feed inherits decisions made earlier in the catalogue. Sustainable optimisation usually means clarifying ownership and correcting data upstream rather than stacking rules in every channel. Read feed rules vs source data.
When to get a second opinion
If spend has changed sharply, products are repeatedly disapproved, coverage is poor or a new feed-management contract is being proposed, an independent review separates data problems from campaign problems before more budget is committed. Start with a free feed triage or use the 40-point checklist.
Where a product attribute can go wrong
Consider a shoe available in UK sizes 7, 8 and 9. The source catalogue holds a parent title and one generic stock number, while the store has three sellable variants. If the export sends the parent’s price and availability with a variant’s URL, Merchant Center may compare the wrong offer. The correct fix often begins with a proper variant record in the ecommerce source, not a rule that hardcodes stock to ‘in stock’.
| Attribute | Source-of-truth check | What customers experience when wrong |
|---|---|---|
id, variant and item group |
Stable mapping to exactly one sellable offer | Wrong colour or size after a Shopping click |
gtin, brand, mpn |
Manufacturer identity, not a generated placeholder | Lower confidence in matching the exact product |
price and availability |
Feed, structured data and landing page agree | Unexpected price or unavailable item |
image_link |
Correct item image, publicly accessible, valid dimensions | Unclear product or image rejection |
Follow the information through the systems
Supplier sheet or ERP → ecommerce product and variant → transformation rules → submitted source → Merchant Center processing → visible landing page. Sample one affected SKU at every point. Document value, timestamp and transformation. Without that chain a feed optimisation can become a temporary patch that is overwritten on the next sync.
Choose a source correction or feed rule deliberately
A feed rule can be sensible when the source stores a valid attribute in the wrong field or a channel needs a different format. Fix the source when identifiers are missing, variants are modelled incorrectly, stock status is unreliable, or teams disagree about the real product data. Read the focused rules versus source data guide for the decision framework.
Build a repeatable quality score
Segment the catalogue by supplier or category and measure attribute completeness, then spot-check accuracy. Do not publish ‘98% clean’ merely because 98% of products have a value: a copied invalid GTIN is filled in but still wrong. Prioritise high-impact and repeatedly failing attributes, preview changes on representative products and keep a rollback plan. The 40-point audit offers a starting checklist; free feed triage is the next step for a live issue.
What changed in 2026 for this issue?
Checked against Google’s announcements on 31 October 2026.
The relevant 2026 changes are below. They do not by themselves explain every problem. Check your Merchant Center diagnostics before acting on an update about product data:
- Bigger minimum image size. From 31 January 2027 product images must be at least 500 x 500 pixels. Smaller images already show the warning “Image too small for upcoming enforcement”. Google will enlarge some small images automatically, but replacing them with proper images is the safer fix (Google’s 2026 product data update).
- Shipping can now be set per product. Since 14 April 2026 you can give individual products their own order cut-off time (handling_cutoff_time) and minimum order value (minimum_order_value), plus loyalty shipping labels. If a few products ship differently, use these rather than stretching your account-wide rules (Google’s 2026 product data update).
- Merchant API migration affects direct API integrations. Google sunset the Content API for Shopping on 18 August 2026. From 1 September 2026, clients without an approved extension may see intermittent HTTP 410 errors; full decommissioning is planned for early 2027. Custom integrations should migrate to the Merchant API. If you use an ecommerce platform’s official Google integration, the platform provider normally manages its API migration. File uploads, scheduled fetches and Google Sheets are separate data-source methods (Google’s official timetable).
Common questions
What is Merchant Center feed optimisation?
Improving the product information you send to Google, such as titles, identifiers, categories and attributes, and the rules that transform it, so products are eligible, matched accurately and presented well.
Does Performance Max fix weak product data?
No. Performance Max relies on the product data it receives. Weak data limits matching and reporting, so clean the feed before scaling spend.
Should I fix data in the feed or at the source?
At the source wherever possible. Feed rules are useful for channel-specific formatting, but source fixes improve every channel at once.
Next step
A Shopping feed problem?
Find the cause.
Send your store and the exact issue. Get a free first look at where to investigate.
Request free feed triage