A topic cluster is a group of articles about one subject that link to each other, with one main article at the centre. Readers can move through the topic without going back to search, and search engines can see that your site covers the subject in depth rather than in scattered pieces.
Most WordPress sites already have clusters without calling them that: every category and tag is a group of articles on a topic. What is usually missing is not the grouping but the linking — and a clear main article.
The three parts of a cluster
The pillar. One article that covers the topic broadly and that every other article in the cluster links to. On a museum site, “Museums in Stockholm” is the pillar; on a recipe site, “Sourdough baking: the complete guide”. A cluster needs one — see Pillar pages.
The supporting articles. Articles that go deeper into one part of the topic: a single museum, a single technique. They link up to the pillar and across to each other where it helps the reader.
The links. The links are what make a group of articles a cluster. An article that nothing links to — an orphan page — is in the category, but not really in the cluster: readers and search engines can only reach it through menus and search.
Why clusters work
Search engines try to judge whether a site knows a subject well, not only whether a single page matches a search. A set of connected articles on one topic is strong evidence of that. Internal links also tell search engines which pages matter most on your site: the pillar that every article points to is the obvious candidate for the broad search, while the supporting articles can rank for the narrower ones.
For readers, the benefit is simpler: they find the next useful article without leaving. That tends to mean more pages per visit, and a reader who trusts the site.
Building a cluster from what you have
- Choose the topic. Start with your categories. A category with 8–40 articles on one coherent subject is a good cluster. Very small ones are better merged; very large ones often hold several topics — see Categories vs tags.
- Pick the pillar. The broadest, most complete article on the topic. If none exists, that is your first article to write.
- Link every article to the pillar — in the text, where the pillar’s subject comes up naturally.
- Link related articles to each other. Not every article to every other one, but the ones a reader of this article would want next. See Internal linking.
- Fix the orphans first. An article nothing links to gains the most from its first link.
- Fill the gaps. Look for the questions your cluster doesn’t answer yet — see Content gaps.
In ClusterIQ
ClusterIQ turns your categories and tags into clusters automatically, gives each one a health score, and picks the pillar — the best-linked article, or the one you choose. Focus next shows the clusters where a few links make the biggest difference, and Improve this cluster lists the fixes, orphans first.
How you know a cluster is healthy
Three things are worth watching, in plain words:
- No orphans. Every article has at least one link from another article.
- Articles link to each other, not only to the pillar.
- One clear main article that the others point to.
Measuring cluster health goes through these one by one, and what to do when a number is low.
Common mistakes
- Too many “main” articles. When five articles all compete to be the main one, none of them stands out. Choose one.
- Overlapping clusters. A category and a tag covering the same subject split your links and can compete in search — see Keyword cannibalisation.
- Links only in menus and sidebars. Links inside the text, in context, are the ones that carry meaning.
- Chasing numbers. A link should help the reader. If it doesn’t, it isn’t worth adding, whatever a score says.