Digital platforms are charactized by their multi-sidedness; various user groups (including buyers and sellers) use platforms to connect and transact with each other. This multi-sidedness can trigger distinct market and competitive dynamics, including (indirect) network effects and winner-takes-all competition, which hold strategic implications for both the firms that control these platforms and the ones operating within them. How do platforms successfully compete with each other? How can platforms effectively govern their ecosystems? How are complementors affected by platform-level dynamics? Under what conditions do winner-take-all dynamics emerge in platform competition?