There are plenty of ad tech companies vying for business out there, but the hottest ones may not be the most well-known... yet. The market for new ad tech businesses may have simmered down considerably (at least in the public forum), but the companies on this list of pre-IPO ad tech startups prove that there's still a ton of money to be made. Though they aren't public yet, don't be surprised to see these companies making a big leap in the not-so-distant future. VCs are betting on them to be the next big thing, assuming they aren't already there.
list ordered by