Click depth

Discoverability: a page reachable only through a long chain is reached by fewer visitors and crawled less often.

Perceived importance: a site's own linking structure is a statement about what it considers central, and depth is a rough summary of that statement.

Crawl efficiency: a crawler working through a large site allocates effort, and deep pages are revisited less frequently.

None of those is depth itself, which is why a deep page linked prominently from a popular section behaves quite differently from a deep page linked once.

It originated as a usability rule of thumb and has no basis in how any search engine ranks or crawls.

A well-structured site with clear categories can put useful content four or five hops away and have it found without difficulty.

Conversely a page two hops away, linked from a footer nobody reads, is effectively invisible.

What matters is whether the path is one a reader would take, which is a judgement the number does not capture.

Which is why it is reported as a measurement with context rather than as a threshold to satisfy.

Pagination that only links a few pages ahead, so anything past that is reachable only by editing a URL.

Faceted navigation, where the useful pages are combinations nobody links to directly.

Content organised by date alone, where an old article is reachable only through an archive nobody traverses.

Links inserted by script after load, which are absent from the markup a crawler reads regardless of how shallow they make the page look to a person.

Category and hub pages that link to the content beneath them, which is what turns a deep tree into a shallow one.

Breadcrumbs, which both shorten paths and tell a reader where they are.

Contextual links between related pages, which cut across the hierarchy rather than following it.

A sitemap does not reduce depth — it aids discovery and changes nothing about the linking structure the depth measures.

Depth, orphan candidates, breadcrumbs and return-to-home paths are measured from the crawl data already collected.

Measurements are relative to the crawl: a page beyond the budget is unmeasured rather than deep.

The primary navigation is compared across pages, since an inconsistent menu changes depth from one template to another.

Script-inserted links are not in the served markup, so a client-side navigation can make a shallow site measure as deep — which is also what a crawler would conclude.