Crawl Depth
Crawl depth is the number of clicks from your homepage to a given page. Pages three or fewer clicks deep are crawled often and treated as important. Pages buried six or more levels down are crawled rarely and frequently never indexed.
Why it matters for your rankings
Search engines infer importance from how easy a page is to reach. A page you must click seven times to find is one you apparently do not consider important, and Google treats that structural signal seriously.
This is why large ecommerce and publisher sites lose whole product ranges to obscurity. Items sit behind category, subcategory, filter and pagination layers until they are effectively invisible to crawlers, no matter how good the individual page is. Depth is also fixable without new content: adding hub pages, related links and sensible pagination can pull thousands of URLs from depth eight to depth three in one change, and indexation usually follows within weeks.
How to check it on your site
Measure it
Crawl with Screaming Frog and open the Site Structure tab. It shows how many URLs sit at each depth level.
Find the deep money pages
Sort your crawl by depth and flag anything commercially important sitting deeper than four clicks.
Flatten with hubs and links
Add category hubs, 'related' modules and contextual internal links from high-authority pages to pull deep URLs upward.
Check pagination
Long paginated series push later items very deep. Increase items per page or add filtered entry points to shorten the path.