Topic cluster strategy is an internal linking architecture where you build one comprehensive pillar page covering a broad topic at a high level, then create 8–20+ cluster pages that each explore a specific subtopic in depth. Every cluster page links back to the pillar, and the pillar links out to all clusters. This creates a hub-and-spoke model that tells Google you own the entire topic, not just random keywords. The pillar page targets a high-volume head term like "content marketing" and covers it in 2,000–4,000 words without going too deep into any one area. Cluster pages target long-tail variations like "content marketing metrics" or "content marketing for SaaS" and each run 800–1,500 words with tactical depth. The internal links pass authority bidirectionally and help users navigate related concepts without leaving your site. This approach works because Google's algorithm has shifted from matching keywords to understanding semantic relationships. When you interlink related content tightly, you build topical authority faster than scattering posts across unrelated subjects. We've seen pillar-cluster setups rank for 40–60% more keywords in the topic space within six months compared to standalone posts. At Ottawa SEO, we typically start with competitive keyword research to map out the pillar term and 10–15 viable clusters. Not every topic needs a cluster—if you're covering "Ottawa web design pricing" you probably don't need a whole pillar, just a solid standalone page. Clusters make sense when search volume and user intent fragment across multiple subtopics. The mistake most sites make is building the pillar first without the clusters, or writing clusters that don't genuinely support the pillar topic. You also need to avoid keyword cannibalization—each cluster should target distinct intent, not variations of the same query. Done right, topic clusters let you dominate a subject vertically instead of chasing random traffic horizontally.