Catalog QA
Catalog QA reads your products and lists the identifiers and details that are duplicated, invalid or missing, with a link to each product so you can fix it. It never changes your products.
Variants that share a SKU or a barcode, including the same GTIN typed as UPC on one and EAN on another.
GTIN, UPC, EAN and ISBN values are checked against their check digit and length rules, including old untyped barcodes.
Variants with no barcode or weight, products with no category or images, images with no alt text, and zero prices.
Install Catalog QA from the Shopify App Store, then open it from Apps in your Shopify admin.