Flat File

A flat file is, at heart, a structured spreadsheet. Each row represents one product, and each column represents one attribute of that product — title, brand, price, quantity, GTIN, bullet points, and so on. By filling in many rows and uploading the file once, a seller can create or update a large catalogue far faster than editing listings one by one in the marketplace interface.

The term "flat" refers to the format: the data is laid out in a plain, two-dimensional grid with no nested structure, usually saved as a tab-separated text file even when prepared in Excel. Amazon's templates add a couple of header rows that tell the system which template version and category the file belongs to, but the body is simply rows of product data.

Crucially, the available columns are category-specific. The flat file for clothing asks for size, colour and material; the one for electronics asks for wattage and connectivity. Amazon publishes a dedicated template for each category, each with its own required fields, optional fields and lists of valid values you must choose from.

Creating new listings in bulk is the obvious use, but flat files are equally important for maintenance. You can use them to update prices across hundreds of SKUs at once, push new stock figures, change images, correct titles, or set up variation relationships between parent and child products. For large catalogues, the flat file is often the only practical way to make sweeping changes.

Because the same template structure underlies marketplace feeds, flat files also sit behind a lot of automation. When a tool syncs your store to a marketplace, it is frequently generating and submitting a flat file or its API-feed equivalent under the hood. Understanding the template helps you diagnose why a listing did or did not publish.

Flat files are powerful but unforgiving. A missing required field, an invalid value that is not on the marketplace's accepted list, a malformed GTIN, or an incorrect template version can cause individual rows — or the whole upload — to be rejected. The error reports can be terse, which is why flat-file troubleshooting is a recurring source of seller frustration.

The reliable defences are using the current template for the right category, filling every required field, choosing values only from the provided valid-value lists, and validating data before upload rather than after. For multichannel sellers, keeping clean, complete source data in your store means the flat files generated for each marketplace start from a correct base, which sharply reduces rejections.