Simply choose categories for export and all products associated with selected categories will be exported.
If given products belongs to more categories, it will exported only once in the following way:
- If the products belongs to the two categories on the same level, the product will be exported from the first category in category tree.
- If the products belongs to a category and also to its subcategory, the product will be exported from the subcategory.
These rules are here because if any product was present in the XML/CSV file several times, the XML/CSL would be very likely rejected by Feed authority. Consider these rules especially when you export products wilth full URL path, including the category URL keys. On other words, when you use full product URL in your Magento frontend.
Category filter is active only if at least one category is selected.