@jaseg it's a JS API that records ad impressions and conversions (the caller is entirely arbitrary, doesn't have to be part of a script that would be blocked by adblock) which provides cross-site attribution of conversions, i.e. the thing GDPR says you need consent for when cookies are involved. the impression may come from a page with sponsored content (e.g. a review) rather than direct display ads, for example. the conversion may be on any e-commerce site.