What Is an SKU? How to Create a Stock Code

The short answer to what an SKU is: an SKU (Stock Keeping Unit) is the stock code a seller assigns to tell each product and each variant apart. A barcode is the product's universal identity, while an SKU is your internal code; the black size M and black size L of the same T-shirt are two separate SKUs.

What is an SKU, and how is it different from a barcode and a model code?

When you upload products to a marketplace, you come across three different identifier fields. Trendyol's product creation documentation illustrates the difference well:

In short: the model code answers "which model," the SKU answers "which variant, in my system," and the barcode answers "which product, in everyone's system." We cover barcodes in detail in our what is a barcode article.

What should a good SKU template look like?

Since you assign the SKU yourself, no rule is imposed, but a good template will make your work easier for years. We recommend these principles:

• Segmented structure: Separate the category, model, attribute and variant segments with hyphens.
• Short, meaningful abbreviations: Anyone reading the code in the warehouse should understand what it is.
• Don't use Turkish characters or spaces: Some systems may interpret codes containing "ş", "ğ" or spaces differently; uppercase letters and digits are the safest choice.
• Don't start with a zero: Spreadsheets like Excel may delete the leading zero, breaking the code.
• Never reuse a code: Giving a discontinued product's code to a new product mixes up old order and return records.
• Same SKU for the same product on every channel: The same variant should carry the same code on Trendyol, Hepsiburada, n11 and Amazon.

SKU template examples

In the last two rows, the model code (productMainId) can be the same, for example "TST-OVR-PMK"; that way Trendyol groups these variants as options of a single model.

Keep your abbreviation list (such as VZO: vazo/vase, KLF: kılıf/case, SYH: siyah/black) in a table and make sure everyone on the team uses the same list. Coding the same color as "SYH" on one product and "SIYAH" on another scatters your products across searches and reports.

Why does the SKU matter in multichannel selling?

When you sell on more than one marketplace, the SKU is the key that ties all channels to a single inventory record:

1. Inventory matching: Stock is deducted from whichever SKU an order from Trendyol belongs to, and updated stock is sent to the other channels through that same SKU. We explain this process in detail in our what is inventory synchronization article.
2. Invoice lines: Even if the product name on the invoice varies by channel, keeping the SKU the same makes sales reports and stock movements consistent. For invoicing marketplace orders, see our marketplace invoicing guide.
3. Returns and warehouse: The SKU label instantly shows which variant a returned item is; the product goes back to the right shelf and the right stock.
4. Image and content management: Naming image files by SKU makes matching easier in a catalog of hundreds of products.