Topic clusters are one of those concepts that everyone agrees with in principle and most sites execute poorly in practice. The idea is straightforward — a hub page covering a broad topic, supported by depth pages covering specific aspects of it, all interconnected through internal links. In practice, the clusters that most sites have built are thematically organized but structurally disconnected, producing the appearance of a topic cluster without the authority consolidation that makes it work.
Why most topic clusters fail to deliver
The failure pattern is consistent. A hub page is created. Several supporting articles are written. They are loosely linked. Traffic improves briefly. Then the cluster plateaus far below its potential. The diagnosis is almost always the same: the internal linking is incomplete, the hub page is too thin to carry the authority its position requires, or the spoke pages are too broad to serve the specificity function that depth pages need to perform.
A topic cluster works as an authority consolidation mechanism only when every structural element is functioning correctly. One weak link in the chain — an underpowered hub, orphaned spokes, generic internal anchor text — undermines the whole system.
What a properly functioning cluster looks like
The hub page should be the most comprehensive, authoritative piece on the broad topic that the site is capable of producing. It should cover the topic at a level that justifies linking out to depth pages — not because it is too long, but because depth pages can go further on specific subtopics than the hub should attempt. A hub that is too thin relative to the breadth of the topic it claims to cover is not functioning as an authority anchor.
Spoke pages should each target a specific, distinct subtopic with enough depth to rank independently for their specific queries. The test is whether each spoke page could stand alone as a useful page for someone who arrived at it without visiting the hub. If yes, it is functioning correctly. If it only makes sense in the context of the hub, it is too dependent and too thin.
The internal linking structure that makes clusters work
Hub to all spokes
Every spoke page should receive a link from the hub with descriptive anchor text that reflects the specific subtopic. This is the primary authority signal that flows from hub to spoke. Missing hub-to-spoke links are the most common structural failure in topic clusters.
Spokes back to hub
Every spoke page should link back to the hub. This creates the authority loop that reinforces the hub’s topical signal. Spokes that link outward to external sites but not back to their hub are distributing authority away from the cluster rather than consolidating it.
Spoke to spoke where genuinely relevant
Related spokes should link to each other when the connection is genuinely useful to a reader. These lateral links strengthen the topic graph and distribute authority within the cluster. They should not be forced — a link from one spoke to an unrelated spoke creates noise in the topic signal rather than strengthening it.
Use SEO Sets to audit your existing topic clusters for internal linking gaps, hub page strength, and spoke page depth — and to identify which clusters are closest to functioning correctly versus which need foundational work before they will consolidate authority effectively.
Frequently asked questions
How many spoke pages should a topic cluster have?
Enough to cover the distinct subtopics within the hub’s scope with genuine depth — typically six to fifteen for most topics. Fewer than five often means the topic hasn’t been covered with enough specificity. More than twenty suggests the topic scope may be too broad for a single cluster.
Can a site have multiple topic clusters simultaneously?
Yes. A site with clear topic authority goals should have multiple clusters, each anchored by a hub page in its respective topic area. The clusters should be distinct enough that their hub pages are not competing with each other.
What should a hub page’s word count be?
Long enough to genuinely overview the topic and contextualise all the subtopics the spokes cover — typically 1,500 to 3,000 words. The word count is secondary to the quality and comprehensiveness of the coverage.
Should spoke pages link to external sources?
Yes, where those sources substantiate specific claims. Linking to authoritative external sources on a spoke page does not undermine the cluster — it reinforces the credibility of the specific claims being made. The key is that the spoke also links back to the hub.
How long does it take for a new topic cluster to produce ranking results?
Three to six months for a new cluster on a site with established domain signals. Clusters built on sites with lower authority take longer. Clusters that fill a genuine gap in the existing content landscape produce results faster than those entering well-covered territory.
