Feed rules and supplemental feeds: transforming the catalogue without touching the website

The feed that comes out of the shop is rarely the feed Shopping needs: ERP titles, in-house categories, no margin labels. And every change "on the website" goes through a developer and a task queue. Merchant Center has two tools for transforming the feed without touching the shop: attribute rules and supplemental feeds. Whoever masters them manages the catalogue from marketing.

Attribute rules

Inside Merchant → Products → Feeds (or Data sources) → your feed → Rules. Each rule defines, for one attribute, where its value comes from and what transformations are applied to it, with optional conditions. Three uses:

1. Mapping columns

Your file has "product_name" and Google wants title: the rule assigns a column to an attribute. The same goes for in-house categories → google_product_category (with conditions: if product_type contains "trainers" → category X).

2. Filling in missing values

If brand is empty → a fixed value "My Brand". If availability is missing → "in stock" (carefully). If shipping does not come through → shipping rules by country.

3. Transforming: building titles and labels

The most powerful operation: concatenating attributes with fixed text. title = brand + " " + gender + " " + product_type + " " + original_title + " " + color + " Size " + size. With conditions by category, you have the title template from lesson 2 applied to the whole catalogue in five minutes, reversible and with no developer.

And calculated custom labels: custom_label_0 = "high_margin" if price > 100 and product_type contains "premium"; custom_label_1 = "on_sale" if sale_price exists; custom_label_2 = "new_arrival" if the date it was added is recent (if you send it in a custom attribute). The campaign structure by margin (module 5) is born here.

Rules can: assign, concatenate, extract (by regular expression), find and replace, split, convert to upper/lower case, calculate, and "take the value from" another feed. They are tested with a preview before being applied.

Supplemental feeds

A supplemental feed is a separate table (usually a Google spreadsheet) with the id column and whatever columns you want to overwrite or add: title, custom_label_0, product_highlight… Merchant matches on id and applies those values on top of the primary feed. Uses:

• Rewritten titles for the 200 products with the most spend, without touching the other 3,000 or the website.
• Margins per product in custom_label_0, maintained by finance in a spreadsheet.
• Temporary exclusions (excluded_destination) for products you do not want advertised this week.
• New attributes the platform does not export (product_detail, material).

It is the day-to-day working tool of anyone optimising Shopping: a spreadsheet marketing controls, applied at the next update and reverted by deleting the row.

Rule or supplemental: which to use

The workflow with no developer

1. Primary feed from the platform, untouched.
2. Rules to normalise (brand, category, product type, title by template, calculated labels).
3. Supplemental spreadsheet for exceptions and for whatever changes often: bespoke titles, margins, exclusions, highlights.
4. Preview and diagnostics after every change; review disapprovals the next day.
5. A log: which rule/row was changed, when and why (a title change is a test: lesson 6).

Common mistakes

• Rules that overwrite a good attribute with an empty one (badly set condition): always preview.
• A supplemental feed whose id values do not match (capitals, spaces): it does not apply and nobody notices.
• Forgetting that the supplemental feed does not create products: it only modifies the ones that exist in the primary feed.
• Titles concatenated with empty attributes → «Nike Running Shoes Size» with gaps: make the concatenation conditional on the attribute existing.

💡 Ninja trick: the titles the Shopping Ninja proposes are designed for this workflow: they are exported as a supplemental spreadsheet (id + title) ready to connect to Merchant. Approve with the checkbox, paste into the spreadsheet, wait for the next feed update — and the original title stays intact on the website in case you need to go back.

What you should remember

• Attribute rules: map, complete and transform (templated titles, calculated labels) with conditions; always with a preview.
• Supplemental feed: a spreadsheet by id that overwrites columns; bespoke titles, margins, exclusions.
• Rules for the mass changes, supplemental for the specific ones.
• The feed is managed from marketing, without touching the website.