The most natural way to design categories looks like a chest of drawers: big drawers with smaller drawers inside. It is how we organise files, so the hand reaches for it first.
But a website category is not a drawer. A folder only exists when you open it, whereas a category is itself a public page. Create one and you have created a URL, which search engines will judge as a page of your site. That single fact changes the whole design.
What sub-categories actually produce
Suppose you put “caching”, “images” and “database” under “performance”. It looks tidy. But each of those starts life holding one or two posts.
You have just created three pages with almost nothing on them. They offer little to a reader and little to a search engine — and worse, all three compete with the parent for the same subject. The weight that should have accumulated on one page is now split four ways.
Flat, and somewhere between five and eight
The shape to aim for is flat, with no hierarchy, and five to eight categories. The range is not arbitrary.
Too few — two or three — and a category is effectively “all posts”, so classifying achieves nothing. Too many, past fifteen, and no archive ever fills up while every new post triggers a filing debate. The debate itself is the signal that you have sliced too finely.
Size the set against the year of writing ahead of you, not the posts you have today. If you cannot picture ten posts landing in a category, that category is premature.
One category per post
WordPress will happily let you tick several categories on one post. It feels convenient, but as a habit it means the same post appears in several archives. The listings start to look alike and each page becomes vaguer about what it is for.
The rule is simple: exactly one category. When a post feels like both SEO and performance, the question to ask is “which archive do I want this read in?”. Themes that genuinely cut across subjects belong to tags, which is the next part.
Unwinding a hierarchy you already have
Do this carefully, because deleting a category turns its URL into a 404. The order is: move the posts up to the parent, confirm the move, delete the child category, then 301 the old address to the parent.
Skip the redirect and every shared or indexed link to those archives breaks. Losing links while improving structure is a poor trade.
How classification feeds into search visibility runs through other articles in the SEO archive, and if you would like a restructure handled alongside a wider review, our process page sets out how the work actually runs.
Next part
Flattening categories leaves an obvious question: where do the finer subjects go? The answer is tags — with one condition attached.