Glossary
Index coverage is the state of your URLs in a search engine's index: which are indexed, which were crawled and excluded, and which were never fetched. It is the difference between publishing a page and having it eligible to rank.
A page can exist, return a healthy response and still be absent from the index because the engine crawled it and decided not to keep it. Until a page is indexed it cannot rank for anything, which makes coverage the first thing to check when new content appears to do nothing.
'Discovered, not indexed' usually means the engine has not judged the page worth fetching yet, often a quality or internal-linking signal. 'Crawled, not indexed' means it looked and declined, which points at thin or duplicative content. 'Alternate page with canonical' means it is being folded into another URL, which is correct behaviour if that was the intent.
Each silently removes a whole section from eligibility.
A steady drift of pages out of the index is a symptom worth investigating long before traffic reflects it.
Common causes are a noindex directive, a canonical pointing elsewhere, a robots rule blocking the path, or the engine judging the page too thin or too similar to an existing one. The exclusion reason reported in search console distinguishes them.
For an established site with healthy internal linking, days rather than weeks is typical. Consistently slow indexing of new pages usually points at crawl or quality signals rather than at the individual page.
Index coverage is the state of your URLs in a search engine's index: which are indexed, which were crawled and excluded, and which were never fetched. It is the difference between publishing a page and having it eligible to rank.
