When two product pages are equally well optimized on-page, the meaningful remaining variable is how much internal link equity and crawl attention each is actually receiving, and that’s determined substantially by the parent category page each is nested under: how authoritative that category page itself is, how prominently the product is featured on it, and how many other internal links compete for the same equity on that page. A product nested under a well-linked, high-authority category, or featured prominently near the top of that category’s listing, inherits meaningfully more internal authority than an identical product buried deeper in a weaker category or listed far down a long product grid, and that gap in inherited authority can fully account for a ranking difference even when every on-page factor is held equal.
Mechanism: category pages as authority-distribution hubs
Internal link equity flows through a site’s link graph in a way that’s long been understood through PageRank-style reasoning: a page’s own authority (built from external backlinks, internal links pointing to it, sitemap presence, and general prominence in the site structure) gets distributed to the pages it links to, divided in some fashion across those outbound links. A category page functions as a hub in this graph for every product nested beneath it. If that category page itself has strong external backlinks, prominent internal linking from the homepage and navigation, and reasonable traffic, it has more authority to redistribute to its child products in the first place. A category page that’s weakly linked, buried in navigation, or has few external signals pointing to it simply has less authority to pass down, regardless of how good the products underneath it are.
Within a given category page, position and prominence matter too. A product featured near the top of a category listing, in a “bestseller” module, or in a smaller total set of linked products on that page typically receives a larger effective share of that page’s outbound link equity than a product listed on page four of forty in a long paginated grid, or one competing against hundreds of sibling links for a share of the same equity pool. Two identically optimized products can therefore receive substantially different internal authority purely based on where each sits within its parent category’s link structure, independent of anything about the product page itself.
This is exactly the mechanism the premise of the question isolates: with on-page optimization held equal between the two products, internal link equity inherited through the category structure becomes the dominant explainable variable left. It’s consistent with well-established, non-Google-specific link-graph reasoning about how authority distributes through a hierarchical site, not a disclosed Google-specific formula, but it’s about as solid a piece of practitioner consensus as exists in technical SEO.
What this doesn’t mean
It’s worth being careful not to overstate this into “on-page optimization doesn’t matter.” The premise of the question specifically holds on-page factors equal to isolate the internal-linking variable; in real, non-hypothetical situations, on-page relevance, content depth, and page quality remain necessary conditions for ranking well, and no amount of internal link equity rescues a genuinely weak or thin product page. What this mechanism explains is the specific, narrower scenario where two pages are doing everything else the same and still diverge, not a general claim that internal linking dominates every ranking outcome regardless of content quality.
Practical implication
The actionable response is auditing category-level link structure rather than re-optimizing product pages that are already doing their on-page job well. Concretely: check whether underperforming products sit under categories with meaningfully weaker external and internal signals than the categories housing comparably strong-performing products, since strengthening the category itself (better internal linking to it from navigation and other high-authority pages, ensuring it earns its own external links where relevant) lifts every product nested beneath it rather than requiring page-by-page fixes.
Check position and prominence within the category page itself: whether the underperforming product is buried deep in pagination or a long unsegmented grid versus prominently featured, and whether category page design (bestseller modules, featured sections, sort order) is systematically advantaging certain products over comparable others in ways that don’t reflect actual product quality or business priority.
Consider whether category page architecture is creating unintended equity concentration, for instance a small number of “featured” categories receiving disproportionate homepage and navigation linking while other categories, and everything nested under them, are comparatively starved. Since the products themselves are equal in this scenario, the fix lives at the category and navigation level, not in further product-page optimization that’s already at parity.
