The Sincera engine crawls a publishers pages (respectfully!) and detects what ad units are on the page, and what ad sizes are declared eligible for that size. For most publishers, there are 3 main identifiers of "Ad Slots" (effectively, spaces on the page where an ad can be displayed. "Ad Unit" and "Ad Element" identifiers are associated with Google's Ad Manager, and "Ad Code" is associated with Prebid. The Sincera engine will stop crawling a page once it has seen 20 consecutive pages without a new, unique Ad Unit, Element, or Code.

Why is this important? By knowing the Ad Unit, Element, and Codes, and their associated eligible ad sizes, publishers can maximize their advertising revenue.