While the various initiatives in several jurisdictions to impose ex ante regulation on “digital gatekeepers” – i.e., large online platforms that are necessary intermediaries between business users and their customers, and which are typically protected by high barriers to entry – have...

We review the burgeoning literature on two-sided markets focusing on the different definitions that have been proposed. In particular, we show that the well-known definition given by Evans is a particular case of the more general definition proposed by Rochet and Tirole. We then identify the...