Product range categorisation is the division of products into a tree of categories and subcategories. It is one of the longest-reaching decisions, because it determines addresses, navigation, filters, and also which pages have a chance of ranking. There are three proven rules. Name categories the way the customer searches for products, not according to an internal code list or the supplier's structure. Keep a reasonable depth – four or more levels means products are too deeply nested and categories are empty. And avoid categories with one or two products, which look unfinished. Every category should have its own description explaining what is in it and how to choose. Plan a change to categorisation as a migration with redirects.
See also: Information architecture, Faceted navigation, Website migration without losing rankings.
