This document discusses citizen engagement platforms used in Amsterdam. It describes how platforms can help connect citizens, policymakers, and innovators to collaborate. However, some policymakers are hesitant due to concerns about costs, maintenance, and control. The document then highlights several examples of successful platforms in Amsterdam, including ones for crowdsourcing ideas, peer-to-peer sharing, and communicating about construction projects. It argues that platforms should be city-wide, use open standards, and incentivize participation to drive engagement and save money. When done right, platforms can transform governance models.