How many categories should a WordPress post have?
One, and two at most. WordPress lets you tick as many categories as you like, but a category works as the post's section of the site, and a post in five sections is in none. Extra categories do not help rankings and make URLs and breadcrumbs unpredictable.
What WordPress does with several categories
Core places no limit on categories per post, and it requires at least one: publish a post with none ticked and WordPress assigns the default category from Settings → Writing, which is Uncategorized on a new site.
With several ticked, a few places can only show one, and core has to choose:
- The URL, when your permalink structure contains
%category%. Core sorts the post's categories by ID and uses the lowest, which is simply the one created first. If that category has a parent, the parent's slug is included too. - Breadcrumbs, in most themes and plugins, which need a single trail from the homepage to the post.
- Schema, where an article names one section.
The oldest category is rarely the most relevant. A post about grinder maintenance filed under "News" (created in 2019) and "Grinders" (created in 2023) gets /news/grinder-maintenance/.
Hydrogen SEO adds a Primary Category choice to the editor's Categories panel when two or more are ticked, and uses your pick for permalinks, breadcrumbs and schema; see primary category. That solves the selection problem. It does not make four categories a good idea.
Why more categories do not help
Each category has an archive page that lists its posts. Assigning a post to a category adds one link to the post from that archive. It does not make the post more relevant for the category's topic, and Google does not rank a post higher for being filed in more places.
What piling on categories does do:
- Blurs the archives. If most posts sit in most categories, the category pages become near-copies of the blog index and of each other. They stop being useful landing pages and compete for the same queries.
- Weakens navigation. Readers use categories to narrow down. A category that contains everything narrows nothing.
- Complicates changes. Renaming, merging or deleting a category later affects many more posts.
A post listed in two archives is not duplicate content, because the archives are lists and the post itself has one URL. The cost is in the quality of those lists.
Categories for sections, tags for details
The simplest working rule:
- A category answers "which section of the site is this in?" Each post has one home. Categories are few, broad and stable.
- A tag answers "what specific things does this mention?" A post can have several. Tags are optional, and a tag used on a single post is not worth creating.
So a post on descaling an espresso machine goes in Maintenance, with tags like descaling and the machine's brand if you have other posts on each.
When a post really does straddle two sections, such as a product review that is also a buying guide, two categories are acceptable. Choose which is primary. If you find most posts need two, your categories overlap and should be redrawn.
How many categories should the site have?
Fewer than most sites end up with. For a blog of up to a few hundred posts, five to ten top-level categories is a workable range. Signs you have too many:
- categories with one or two posts;
- two categories you cannot explain the difference between;
- category names that are really tags ("2026", a person's name, a single product).
Each category should be able to hold at least a handful of posts and keep growing, because its archive is a page Google can index and rank. Thin ones are candidates for merging.
Fixing an over-categorised site
- List categories with their post counts on Posts → Categories. Sort by count.
- Decide the keepers. Merge near-duplicates into the stronger one: move the posts with bulk edit, then delete the emptied category and redirect its archive address to the keeper.
- Reduce each post to one category. Bulk edit can add a category to many posts but not remove one, so work through posts by category filter, or use WP-CLI:
wp post term remove <id> category <slug>. - Mind the URLs. If
%category%is in your permalink structure, changing a post's categories can change its address. WordPress redirects a post requested under a category it no longer belongs to, but set the primary category first and check a few posts. - Re-check navigation and breadcrumbs so they reflect the new, smaller set.
Do this once, deliberately. Category archives that have earned traffic deserve a redirect when they go; see noindexing tag and category archives for deciding which archives should be indexed at all.
Common questions
Can a WordPress post have no category?
No. If you tick none, WordPress assigns the default category when the post is saved.
Is a post in two categories duplicate content?
No. The post has a single URL. It simply appears in two archive lists, which is normal.
Which category shows in the URL when a post has several?
Without a plugin, the one with the lowest ID, meaning the category that was created earliest. A primary category setting lets you choose instead.
Should every post also have tags?
Only where a tag groups several posts on a specific subject. Tags are optional, and unused or single-post tags are clutter.