How to Spot Duplicate SKUs Before They Cost You

A duplicate SKU is one of those problems that looks small until it isn't. In most ecommerce platforms, the SKU is the unique identifier for a product variant. When two rows share the same SKU, the platform has to make a choice — and it usually makes the wrong one.

Why duplicates happen — Supplier spreadsheets are not designed for direct import into an ecommerce platform. They're designed for the supplier's own internal tracking. A supplier might list the same product twice — once in a seasonal catalog and once in their core range — without realizing both rows will end up in your import file.

What happens when you import a duplicate — In Shopify, if you import a file with duplicate SKUs, the second occurrence typically overwrites the first. You might end up with the wrong price, wrong stock level, or wrong variant attributes on a live product without realizing it until a customer complains.

How to find them before import — The manual approach is to open the file in Excel, select the SKU column, and use conditional formatting to highlight duplicates. This works but is easy to miss in a large file. A catalog health check tool like ClearCatalogue can scan the entire file automatically and surface every duplicate SKU with the exact rows where they appear.