It works like this: When a user visits a website that contains Turn tracking code, the company holds an auction within milliseconds for advertisers to target that user. The highest bidder’s ad instantly appears on the user’s screen as the web page loads. Turn says it receives 2 million requests for online advertising placements per second.
For its auctions to work, Turn needs to identify web users by cookies, which are small text files that are stored on their computers. The cookies allow Turn to identify a user’s web browsing habits, such as an interest in sports or shopping, which it uses to lure advertisers to the auction.
Some users try to block such tracking by turning off or deleting cookies. But Turn says that when users clear their cookies, it does not consider that a signal that users want to opt out from being tracked.