Barcode & product-data guides

Amazon and Google ask for the manufacturer GTIN on branded shoes. eBay asks for it in most categories. StockX and GOAT list by catalog match or style code.

Branded shoes need the manufacturer GTIN for each size in a Merchant Center feed. The mpn, brand and identifier_exists attributes cover the cases where no GTIN exists.

Amazon requires a product ID for shoes and lists no exception for the category. eBay requires identifiers in most categories and limits when "Does not apply" may be used.

A GTIN is the GS1 Global Trade Item Number that sits above UPC, EAN and the 14-digit case code as one shared product identifier.

A practical guide to checking that a UPC, EAN, or GTIN is well formed before you trust it.

UPC is not an alternative to GTIN. A UPC-A barcode carries a 12-digit GTIN-12, so UPC is one member of the wider GTIN family.

An EAN-13 barcode is a 13-digit GTIN-13 built from a GS1 prefix, a company prefix, an item reference and a check digit.

GTIN-14 identifies a packaging level such as a case or carton by adding an indicator digit in front of the base product GTIN.

Compute the modulo-10 check digit for any UPC-A or EAN-13 with a pen, paper, and one small rule.

The seven reasons a UPC or EAN check digit fails validation, and how to fix each one.

How UPC-E compresses a 12-digit UPC-A into 8 digits, and why they share a check digit.

A walkthrough for developers: how a barcode API turns a scanned GTIN into structured product data inside your application.

A 200 status is not a successful product match. Learn how to branch on status, the error flag, and the message so you do not treat every miss as a 4xx or as coverage.

A style-code lookup can return many barcodes for one shoe. Learn how to read size and color variant data so you attach the right barcode to inventory.

Comparing one product across forty shops only works if every shop is talking about the same product. That identity problem is a barcode and style-code problem before it is a pricing one.

A catalog assembled from many sources inherits many pictures of the same item. Choosing one, and keeping it loading, is an identifier problem with a hosting problem attached.

Six barcode and UPC database APIs side by side, with the entry price and free tier each vendor published in October 2026.

How to connect a camera scanner to a product-data API so users can scan an item and see what it is.

A field-by-field explanation of what you get back from a product-data barcode API and how to handle uneven results.

The Barcodes.gg API turns a barcode into a structured product record with one authenticated GET request. This guide takes you from token to first response.

Amazon and Google ask for the manufacturer GTIN on branded shoes. eBay asks for it in most categories. StockX and GOAT list by catalog match or style code.

Branded shoes need the manufacturer GTIN for each size in a Merchant Center feed. The mpn, brand and identifier_exists attributes cover the cases where no GTIN exists.

Amazon requires a product ID for shoes and lists no exception for the category. eBay requires identifiers in most categories and limits when "Does not apply" may be used.

A barcode can pass validation and still return no product result. Learn how to separate input errors, normalization issues and catalog misses before accepting or replacing the number.

What a barcode lookup can and cannot tell you about sneaker authenticity, and how to use it as one signal among several.

The difference between looking up a product by SKU or style number and by barcode, and when to use each one for sourcing.

Identifying incoming sneakers by hand is slow and error-prone. A box barcode plus a lookup call turns intake into a scan that auto-fills name, style code, colorway and size.