Topic cluster: A group of pages on one subject: a pillar page and the posts that each answer one part of it, linked to the pillar and to each other where it helps the reader.
Why sites use them
A cluster turns a pile of related posts into something a reader can move through. A gardening site might have a pillar on growing tomatoes and cluster posts on seed starting, staking, feeding, blight and saving seeds. Each cluster post links to the pillar, the pillar links to each of them, and the posts link to each other where it helps (the blight post to the feeding post, say).
The SEO benefit people claim is usually framed as topical authority. That part is debated and hard to measure. The parts that are not debated are more practical: every post in the cluster is linked, so none are orphans; the pillar collects links from several related pages; and readers who arrive on a narrow post can find the overview. Google’s SEO starter guide also notes that grouping similar topics in directories can help it understand how often URLs in each part of a site change.
Building one in WordPress
- Pick a topic you already have five or more posts on. A cluster of two is just a link.
- Choose or write the pillar, then add links from each cluster post in a sentence that mentions the broader topic.
- Put the cluster posts in the same category so archives and breadcrumbs back up the structure, but don’t rely on the category page alone.
- Cross-link sibling posts only where the reader would actually want to go next.
Clusters vs silos
A cluster allows links out to other topics when they help: the tomato-blight post can link to the general post on fungicides. A strict silo forbids that. The comparison of silos and topic clusters sets the two side by side with examples.