The Rakuten Category Taxonomy and category list is on a per category basis.
Rakuten categories can be quite intimidating with thousands of categories. The primary category is required as is defined by you. Make sure that top-level categories are used only instead of using bottom-level categories.
Using both top and bottom-level categories as the primary category can be problematic as character limit of category field may be exceeded. Secondary categories are optional and should be delimited with double tildes.
If you’ve ever found yourself asking how do I map my products to Rakuten categories, we can actually do all the heavy lifting! We have a function that can easily map your categories from Google Shopping to every other engine, including Rakuten.
Brian Roizen is the co-founder and chief architect of Feedonomics, a full-service feed optimization platform that optimizes product data for hundreds of channels. He has been featured on numerous podcasts and eCommerce webinars, and regularly contributes to Search Engine Land and other industry-leading blogs. Brian graduated summa cum laude from UCLA with both a Bachelor’s and Master’s degree in Mechanical Engineering.