What it means
Ranking overlap is the portion of queries or topics where more than one site ranks at the same time. You measure it to see how much your visibility intersects with a competitor's and how contested a topic is. The more queries where you and a rival both appear, the more directly you compete for the same demand, which is a practical read on topical competitiveness and the authority you need to win.
Why it matters
Overlap tells you where authority is shared and where it is not. Kevin's cross-engine research shows overlap is not uniform: Guides and tutorials share the most ground, while product pages and homepages share the least. Compared against your competitors, low overlap on a topic can signal an opening, and high overlap means you need more topical depth to break through.
Say a mid-market B2B SaaS company maps its top 300 commercial queries against 2 competitors. It finds 70% overlap with one rival on "alternatives" and "versus" queries but only 15% on how-to topics. The team shifts content investment into the low-overlap how-to space, where authority is easier to build, and picks up rankings on 40 new queries within a quarter.
How to use this knowledge
Pull the queries you rank for and intersect them with each key competitor to get an overlap percentage per topic. Treat high overlap as a contested area that needs more topical depth, meaning more complete coverage of the entities and questions, to win. Treat low overlap as either an opening or an irrelevant space, and validate it against real demand before you invest. Segment overlap by page type, since explanatory content overlaps and travels further than brand or product pages.
Growth Memo guidance
Topical relevance, ie, how completely a site covers related entities and questions, is a real and important factor in ranking. — How to measure topical authority
Guides and tutorials have the highest cross-engine overlap at 2.3%, followed by blogs at 1.8%, category pages at 1.6%, product pages at 1.2%, and homepages at 1.1%. — The Consensus Gap
One of the lowest hanging fruits in SEO is to create content for "alternative" and "versus" queries. — 3 best practices of competitor SEO you should know
Topical authority — the depth of coverage that decides who wins the high-overlap queries.
Keyword cannibalization — internal overlap, where 2 of your own pages compete for one query.
Competitor SEO — using "alternative" and "versus" queries to deliberately overlap with a rival's demand.
Cross-engine overlap — the AI-search version, measuring how often the same source is cited across ChatGPT, Perplexity, and AI Overviews.
Share of voice — the aggregate visibility metric that overlap analysis rolls up into.