It's worth noting that the user ID sync only needs to happen once per bidder in the real-time auction that determines which ads get served - once the bidder's u

It's worth noting that the user ID sync only needs to happen once per bidder in the real-time auction that determines which ads get served - once the bidder's user ID is linked to the auction provider's user ID, no more cookies need to get set. A typical user who landed on this page as part of their normal everyday browsing wouldn't have nearly so many cookies written - because this site is being tested in isolation, it's a bit misleading. This is probably why the parent here only saw 37 cookies, vs. the tester's 139.