The index grows from the networks' own seller files, so most sites arrive on their own. If one you care about is missing, here is how to queue it — and what has to be true for it to appear.
Email the domain to [email protected] with the subject “Submit”. One domain per line, no other formalities. We queue it for the crawler, which reads its ads.txt, fetches its homepage and checks it against every tracked network's seller file. The crawler runs in batches rather than continuously, so a submitted site can take a while to appear. To see straight away which networks a site’s ads.txt names, search for the domain — for a site we do not have yet, the search reads its ads.txt on the spot.
A site earns a page when there is something verifiable to say about it: a tracked network's seller file lists it, or its own ads.txt names a tracked network. A site with neither has no relationship for us to record, and adding it would just be a page with nothing on it. Submitting cannot make a network's file say something it doesn't — that part is between the site and its network, which is rather the point of the method.
Sites also stay off the index while they have nothing to compare against — no niche classification yet, or a homepage that could not be read. Those usually resolve within a few crawl cycles.