We study the design of online platforms that aggregate information and facilitate transac tions. Two different designs can be observed in the market: revealing platforms that disclose the identity of transaction partners (e.g. Booking) and anonymous platforms that do not (e.g. Hotwire). To analyse the implications of this design choice for profits and surplus, we develop a model in which consumers differ in their location as well as their preferred product variety. Sellers offer their products for sale both directly (`offline') and indirectly via the platform (`online') but are unable to credibly disclose the product variety they offer when selling offline. The model gives rise to a novel trade-off associated with the anonymous platform design: offline, consumers observe location but not variety; online, they observe variety but not location. While the revealing design leads to more informed consumers and better matches, the anonymous design allows sellers to price discriminate and introduces competition between sellers whose markets would otherwise be segmented. We show that the comparison between the designs depends crucially on the relative importance of information about location vis-à-vis information about variety. For an intermediate range, the anonymous design outperforms the revealing design in terms of both profits and welfare.
