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GMC (Google Merchant Center)
#The product-feed hub Google uses to populate Shopping ads, Free Listings, and Performance Max.
GMC is where Shopping performance is decided. Item disapprovals, account suspensions, store-quality flags, and feed validation all happen here, and most of them go un-fixed for weeks because nobody is checking the GMC dashboard. The accounts that win in Shopping treat GMC monitoring as a daily job, not a quarterly cleanup.
Google's account-level penalty that stops all Shopping and PMax product traffic until the suspension is lifted.
GMC suspensions kill ecom revenue overnight and most agencies don't have a recovery playbook. The two most common causes are misrepresentation (price/availability mismatch between feed and PDP) and policy violations (restricted product category, missing pages). Recovery is feed surgery plus a written reconsideration request to a real Google reviewer, not a button click.
IGMC flag on individual products that prevents them showing in Shopping ads, while the rest of the feed runs.
Item disapprovals look minor but compound: one disapproved product on a hero SKU is a revenue leak you never see in the campaign dashboard. Feed rules and custom labels can prevent them at submission time. The audit-ready accounts have a daily disapproval-count check that pages the buyer when the number spikes.
FThe 70+ structured fields (title, description, custom label, price, GTIN, etc.) that describe each product to Google.
Feed columns are the highest-leverage work in Shopping and most agencies don't do them. Title structure alone (brand → product type → key attribute → variant) is worth 10-30% of ROAS in most accounts. Custom labels turn into PMax asset-group splits. GTIN compliance keeps you out of restricted-category bans.
CFive user-defined feed columns (custom_label_0 through custom_label_4) used to group products inside PMax and Shopping.
Custom labels are the bridge between the feed and PMax structure. Tagged correctly (margin tier, seasonality, hero SKU flag, new arrival) they let you split asset groups and protect high-margin SKUs from PMax's auto-allocation. Tagged lazy or not at all, you're running PMax with one big asset group and praying.
FGMC's transformation engine that lets you modify feed values at submission without touching your Shopify export.
Feed rules let you patch a broken feed without engineering work. The pattern most agencies miss: build feed rules to enforce a title structure, fill missing custom labels from product type, exclude restricted SKUs by GTIN range. It's the difference between a feed audit and a feed fix.
PThe main product feed in Google Merchant Center that GMC reads first to populate your catalog.
Primary feed is the source of truth for the catalog: title, description, image, price, availability, GTIN, brand, product type. Almost every ecom account has exactly one primary feed (their Shopify product feed) and most of the leverage is in cleaning that feed up before reaching for supplemental feeds.
SAn additional feed that overrides or augments specific columns of the primary feed without replacing it.
Supplemental feeds are the surgical tool for fixing GMC issues without forking your Shopify feed. The most common use case is custom_label_0..4 (margin tier, performance tier, seasonality), title overrides for specific SKUs, and fixing GTIN errors on imported brands. Layer them rather than rewriting the primary.
GGlobal Trade Item Number. The barcode-style identifier Google uses to match your products to its catalog.
Missing or invalid GTINs are one of the top three causes of GMC item disapprovals on third-party-brand resellers. Google strongly prefers feeds with GTIN populated because it can then verify the product against its own catalog. For private-label brands without GTINs, the identifier_exists attribute set to FALSE is the correct workaround.
MManufacturer Part Number. A secondary product identifier Google accepts when GTIN is unavailable.
MPN is the fallback when a product has no GTIN, in combination with the brand attribute. Together they let GMC match the product to its catalog. Private-label ecom brands without GTINs can usually skip MPN too if they set identifier_exists to FALSE, but for resellers MPN is essential.
BThe required feed field naming the manufacturer or designer of the product.
The brand attribute is non-negotiable for GMC submission and Google uses it for matching, search filtering, and brand-restriction logic. Misspelling brand names is a quiet leak across 1000-SKU feeds. Run a sanity diff against the canonical brand list quarterly.
PYour own taxonomy of product categories, declared in the product_type feed column.
Product types are the most-skipped feed lever. They're what asset groups inside PMax can filter on cleanly: 'Apparel > Tops > T-shirts' lets you build an asset group for tops only. Most accounts leave product_type blank or duplicate the Google product category, and miss the routing leverage.
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Google product category
#Google's standardised product taxonomy, around 6000 categories deep. Used for matching and policy enforcement.
Google product category is set by Google's matching when you submit a product, but you can override it. Mis-categorisation triggers a wide range of policy issues (apparel categorised as healthcare, supplements categorised as cosmetics) and the wrong category sometimes restricts the product from auction eligibility entirely. Audit the assigned category against your product type for every category change.
AThe feed attribute declaring whether a product is in_stock, out_of_stock, preorder, or backorder.
Availability drift is one of the silent killers of ecom Shopping. Out-of-stock products that still show as in_stock in the feed get clicks that never convert and quietly burn budget. The fix is a feed connector that updates availability in near-real-time from the Shopify inventory state, not the once-a-day Shopify-default refresh.
PA separate GMC feed for promotional offers (percentage off, free shipping, BOGO) that show as ad annotations.
Promotions feeds add the discount badge to your Shopping ads and almost always lift CTR by a meaningful margin during a promotion window. The setup is a one-time GMC config plus a feed CSV that updates with each promo. Most brands launch a Black Friday promo and forget to wire the promotions feed; that's the easiest CTR lift available during the highest-traffic week of the year.
The 1-5 star rating shown next to your Shopping ad, sourced from approved review providers.
Product ratings need a minimum of 50 reviews per product across approved providers (Yotpo, Reviews.io, Trustpilot, etc.) before GMC will surface them. They lift CTR significantly on Shopping. The setup is a one-time provider integration; the maintenance is making sure the review feed continues to flow.
SGMC-level shipping costs, delivery times, and free-shipping thresholds shown in your Shopping ads.
Shipping settings are configured in GMC, not the feed, but they show as text annotations on the Shopping result. Inaccurate shipping cost is a top cause of item disapprovals and click-to-conversion drop-off. Audit shipping settings every time the rate card changes at the Shopify level.