GTINs and SKUs
How to find, understand, and set product identifiers to improve marketplace visibility and search accuracy
Overview
Product identifiers help marketplaces like Google Shopping and Amazon correctly recognize and display your products. CMS Max supports two types of identifiers: GTINs (barcodes assigned by manufacturers) and SKUs (internal codes you define yourself).
What Is a GTIN?
A GTIN (Global Trade Item Number) is a unique number that manufacturers assign to products. It is the number printed beneath the barcode on product packaging. GTINs allow online marketplaces to accurately match your listing to the correct product in their databases, improving visibility in shopping results.
GTINs are required for any product that a manufacturer has assigned one. They are not required for custom-made, handmade, or vintage items that don't have manufacturer-assigned identifiers.
Important: Only enter a GTIN if you are certain it is correct. Do not guess or make one up — invalid GTINs are automatically rejected by Google Merchant Center.
GTIN Formats
There are four GTIN formats, distinguished by the number of digits. Terms like "UPC" and "EAN" are simply regional names for these same formats.
| Format | Digits | Common Use |
|---|---|---|
| GTIN-8 | 8 digits | Small packages with limited barcode space |
| GTIN-12 (UPC) | 12 digits | North American products; convert UPC-E (8-digit) to UPC-A (12-digit) |
| GTIN-13 (EAN / JAN / ISBN) | 13 digits | European (EAN), Japanese (JAN), and books (ISBN); convert ISBN-10 to ISBN-13 |
| GTIN-14 (ITF-14) | 14 digits | Multipacks and wholesale cases |
UPC, EAN, JAN, and ISBN are not separate systems — they are regional or industry-specific names for the same GTIN standard.
Where to Find a GTIN
Look in these places to find the GTIN for a product:
- Product packaging — The number printed directly below or beside the barcode
- Manufacturer's website or product documentation
- Your supplier or distributor — Contact them directly if the number isn't on the packaging
- Wholesale purchase records — GTINs are often included in invoices or packing slips
- A barcode scanner app — Scan the product barcode to look up the GTIN instantly
Frequently Asked Questions
What if I can't find the GTIN? Contact your supplier or manufacturer and ask for the GTIN or Manufacturer Part Number. If the product is handmade, custom, or vintage, it likely doesn't have one.
How do I get a GTIN for products I manufacture myself? Visit the GS1 website — GS1 is the official organization that issues GTINs. A single GTIN costs approximately $30. A Company Prefix (used to generate 10 or more GTINs) is also available and requires annual renewal.
Do product variations need separate GTINs? Yes. Different sizes, colors, and specifications each require their own GTIN so that marketplaces can match customer searches accurately. Apparel is a common exception — clothing often shares a GTIN across size and color variations.
Can I use a barcode scanner app? Yes. Barcode scanner apps can read barcodes and display the GTIN, as well as verify product details through online databases.
Why are GTINs important for online selling? Major marketplaces including Amazon, Google Shopping, and eBay require GTINs for listed products. Correct GTINs improve search visibility, support international sales, and allow accurate price comparisons. Products that should have a GTIN but don't may receive lower search placement.
Adding a GTIN to a Product
- Navigate to eCommerce > Products and open the product you want to edit.
- Click the Attributes tab.
- Enter the GTIN in the GTIN field.
- If the product is custom-made and has no manufacturer GTIN, select No Identifier instead.
- Click Save.
CMS Max automatically validates the format of the GTIN you enter.