A topic cluster is a group of pages about one subject: one broad hub page and several narrower posts that each answer a single question, all linked to each other. It helps readers follow the whole subject, and it shows search engines and AI assistants how your pages relate.
What does a topic cluster look like?
Picture a hub and its spokes. The hub (often called a pillar page) covers the subject at a high level and points to deeper pages. Each spoke takes one question from the subject and answers it fully. Every spoke links back to the hub and to its closest sibling pages.
This blog is organised that way. Each topic has a hub at /blog/topics/content-strategy that lists its posts, and each post links to its neighbours. You do not need special software for this. A cluster is a plan for what to write next and a habit of linking as you go.
Why do clusters help SEO?
Google does not publish a "cluster ranking factor," so be wary of anyone who says clusters are a formula. The case for them rests on things Google does say. Its helpful content guidance asks whether a reader will "leave feeling they've learned enough about a topic to help achieve their goal." A single post rarely does that for a broad subject. A set of linked posts can.
Links matter too. Google's SEO starter guide says links "can provide more context on a topic, both for users and search engines." Internal links between related posts are the simplest way to give that context.
There is a plain practical reason as well. When every post sits in a clear topic, you can see what is missing. A topic with one post is a gap. A topic with eight is a strength.
How do you build a topic cluster?
- Pick a topic you can own. Choose a subject close to what you sell or know first-hand, narrow enough that you can cover most of its questions. "SEO" is too wide. "Getting cited by AI assistants" is workable.
- List the questions people ask. Use a keyword tool, the "People also ask" box, and your own support emails. Write each question as a candidate post.
- Give each question one page. If two questions have the same answer, they are one post. If one question needs two different answers, they are two.
- Write the answer-first posts before the hub. The hub is easier once you know what the spokes say. Until then, a simple list page works.
- Link as you publish. Each new post links to two or three siblings and to the hub, and you go back and add a link from an older sibling to the new one.
- Review quarterly. Look for questions you skipped, posts that overlap, and old posts that need a refresh. Our guide to refreshing old posts covers the last step.
How many posts should a cluster have?
There is no magic number. Start with the questions your customers actually ask, and publish the ones you can answer better than the pages already ranking. A cluster of five strong posts beats twenty thin ones. Pace matters less than quality, as we explain in how often to blog.
What mistakes do people make with clusters?
- Writing the same post five times. Several posts aimed at one question compete with each other. Merge them or give each a distinct question.
- Linking everything to everything. Links should help a reader take a next step. Three relevant links beat thirty.
- Choosing keywords without checking intent. A post needs to match what the searcher wants, which is the point of our post on search intent.
- Treating the hub as a keyword page. A hub should help someone find the right post, not repeat all of them.
- Abandoning the cluster after three posts. A topic needs coverage before it reads as expertise.
Do clusters matter for AI answers?
Possibly, though no one outside the AI companies can prove it. Google says AI Overviews and AI Mode may use a "query fan-out" technique, issuing "multiple related searches across subtopics and data sources," as described in its AI features documentation. A site with clear, linked answers to the subtopics of a question has more to offer when an assistant looks across subtopics. That is a reasonable inference, not a guarantee.
Nightcrop's pipeline includes cannibalization checks and internal linking for exactly this reason: a cluster only works if its pages do not compete with each other.
Frequently Asked Questions
Is a pillar page the same as a topic cluster?
No. A pillar page is the hub inside a cluster. The cluster is the hub plus the narrower posts linked to it.
Do I need a long pillar page?
Not necessarily. A short hub that lists and describes the posts works, as long as it helps a reader find the right one.
Can one post belong to two clusters?
Pick the cluster the reader is trying to solve, then link to the other cluster's posts from the text. One home per post keeps the structure clear.
How long until a cluster shows results?
It varies with your site's age and competition, and nobody can promise a date. Track impressions in Search Console per post and judge over months, not days.
Should I update the hub when I add a post?
Yes. A new post that the hub does not list is hard to find, for readers and for crawlers.