Not much. Here&#x27;s how our (modern) ad network works:<p>New user seen, gets assigned random UUID like ABC12345. Show an ad based on what we know about site context.<p>Show ad, track that ABC12345 has seen this ad. Next time, we check your history and know to show you a different ad. If you click on anything, we see that as a signal that you perhaps like that category of ads.<p>Eventually we have a list of ads you&#x27;ve seen (to keep the frequency of those ads in check) and what categories you seem interested in (based on your clicks). Combine this with the context of the site and we can give you better ads. We DO NOT magically get your name, address, birthday, or any other personally identifiable information.<p>--<p>Just for more detail: Facebook and Google are different. They are the biggest adtech players and own about 80% of the market not only because of their size but because of how much they know about you. Most people willingly tell both companies everything about their lives so they have a distinct advantage. They also know your identity across devices because of logins. These massive companies are a much much bigger privacy issue than any independent adtech company simply because independent players do not have access to all this detailed 1st party information (or it&#x27;s provided through rough aggregated&#x2F;statistical means).