Seven catalogue errors and how to fix them
Small gaps in product data break stock sync, postage, filters and shopping feeds. Here is what each one does, how to find it in Shopify or WooCommerce, and how to fix it yourself.
None of these errors stops a store from trading, which is why they last. A product with no weight still sells. A variant with no SKU still ships. The cost shows up elsewhere: postage that does not cover the carrier's bill, stock counts that disagree with the warehouse, a brand filter that misses half the range. This guide takes the seven issues our free catalogue check looks for, one at a time.
First, get the whole picture
Fixing errors one product at a time is slow and you will miss some. Start with a full list.
- Shopify: Products, then Export, then all products as a CSV. The columns that matter here are Variant SKU, Variant Grams, Variant Barcode, Type, Vendor and Image Src.
- WooCommerce: Products, then Export, with all columns. Look at SKU, Weight, Categories, Images and your brand field.
- Or let us read it: the catalogue check reads the catalogue your store already publishes and lists every flagged product in seconds. No sign-up and no admin access. See a sample report.
Open the export in a spreadsheet, add a filter to the header row, and work through the sections below.
1. Shared SKUs
What it breaks. Warehouse, stock and marketplace connectors usually match products by SKU. When two variants share one, they share a stock count too. One sells out and the other shows as unavailable, or an item oversells because the connector updated the wrong one.
How to spot it. In the export, sort by SKU and look for the same value on more than one row (in a spreadsheet, a COUNTIF formula on the SKU column flags any SKU used more than once). Shopify does not stop you saving the same SKU twice. WooCommerce rejects duplicates by default, so this is mostly a Shopify issue, often left behind by duplicated products.
How to fix it. Give every variant its own SKU. Agree a pattern first, for example style, then colour, then size, so new products follow it. Shopify’s bulk editor lets you change SKUs for many variants at once. If a 3PL or marketplace already uses the old SKUs, change them there at the same time.
2. Missing SKUs
What it breaks. A variant with no SKU is invisible to any connector that matches by SKU. Its stock has to be kept right by hand, and returns and reorders are harder to trace.
How to spot it. Filter the SKU column for blanks. Check every variant, not only the first one shown on the product.
How to fix it. Add SKUs using the same pattern as above. In WooCommerce, each variation has its own SKU field, separate from the parent product.
3. Missing shipping weights
What it breaks. Where postage is charged by weight, or rates come from the carrier, a variant with no weight goes through checkout as weightless. The postage charged can fall short of what the carrier bills you.
How to spot it. In a Shopify export, filter Variant Grams for 0 on products that ship. In WooCommerce, filter the Weight column for blanks. Products that are genuinely not shipped, such as gift cards or digital goods, should be marked that way rather than left at zero.
How to fix it. Weigh each product as packed, or take the weight from the supplier’s spec sheet. Variants of the same product often share a weight, so fill them together. Shopify’s bulk editor and WooCommerce’s bulk edit both set weight for many items at once.
4. Products with no image
What it breaks. Google Shopping and the marketplaces reject listings without an image, and a product page with a placeholder rarely sells.
How to spot it. Filter Image Src (Shopify) or Images (WooCommerce) for blanks. On Shopify, each product row group should have at least one image line.
How to fix it. This one needs your photos, so no tool can invent it. Prioritise by what sells or what you advertise. Until an image exists, consider hiding the product from sales channels and feeds.
5. Missing product types (categories on WooCommerce)
What it breaks. Automated collections, filters and feed rules are often built on product type or category. Products without one drop out of them, so shoppers browsing by category never see them.
How to spot it. In Shopify, filter the Type column for blanks. In WooCommerce, look for products in Uncategorized, the default category for anything left unassigned.
How to fix it. Choose from your existing list of types or categories rather than creating new ones as you go. Shopify’s product list can be filtered and the bulk editor can set Type for many products at once. WooCommerce bulk edit can assign categories to a selection.
6. Near-duplicate product types
What it breaks. “T-shirt”, “T-Shirts” and “Tshirt” look like one range to a person and three to a system. Filters, collections and reports split one range across separate entries, and its sales across separate report lines.
How to spot it. List every distinct value in the Type or Categories column (a pivot table or the filter drop-down shows them) and read them side by side. Look for plurals, hyphens, capital letters and spelling slips.
How to fix it. Pick one name for each range and write the list down. Change every product to that name, then check any automated collection or feed rule that used the old spellings.
7. Brand spelt two ways
What it breaks. Brand filters and brand reports treat each spelling as a separate brand. Shoppers filtering by brand miss part of the range, and sales by brand stop adding up.
How to spot it. List the distinct values in Vendor (Shopify) or your brand field (WooCommerce) and look for pairs such as “Acme” and “ACME Ltd”.
How to fix it. Choose the spelling the brand itself uses, change every product to match, and add it to your written list so new products follow it.
A note on barcodes
Google Shopping and Amazon expect a GTIN (the barcode number) for branded products, and listings without one can be limited or turned down. Barcodes are not in a store’s public catalogue, so our free check can only spot-check them on a sample. Use the manufacturer’s barcodes and never make one up: an invented number fails validation and can get listings removed.
Keep it clean
Fixing the backlog once is only half the job. Errors return with every new product unless the rules are written down.
- A required-fields checklist for new products: SKU on every variant, weight on every shipped variant, at least one image, a type or category from the agreed list, the brand spelt the agreed way.
- One written list of product types, categories and brand spellings, kept where the whole team can find it.
- A regular re-check. Run the catalogue check again after a big upload or once a month, or automate it so new errors are flagged the night they appear. Our guide to catching data errors before they go live explains how.
Key takeaways
- Start from a full export, not one product at a time.
- Every variant needs its own SKU and, if it ships, a weight.
- Agree one list of product types, categories and brand spellings, and stick to it.
- Images and barcodes must come from you or the manufacturer: never invent them.
- Re-check after big uploads, or automate the check.