Discovery
Also known as: Discoverability
Whether machines and people can find a property at all. The second stage of the framework and the one most reporting cannot see.
Discovery covers everything between publishing a page and somebody being able to reach it: crawling, indexation, retrieval by AI systems, appearing for a query, and being findable by name.
It is measured from two independent streams here. Server request logs show what crawlers actually asked for, when, and what they got back. Search data shows what a search engine chose to surface. The first arrives earlier and covers systems the second will never report on.
Discovery is not visibility and it is certainly not traffic. A property can be thoroughly crawled and completely absent from search results. That is a real state, it is common on new domains, and reading it as failure is the most common misdiagnosis in the first ninety days of a property.