App-based mobility services have brought large consumer benefits by expanding choice and improving service quality, as well as driving down consumer prices and creating new jobs. At the same time, the rapid growth of these new services has given rise to concerns about a range of actual or potential negative impacts, and poses new challenges for policy makers and regulators. This Going Digital Toolkit note identifies key issues and principles that policy makers should consider when regulating app-based mobility services. It also discusses the key regulatory dynamics affecting the markets for ridesourcing, e-scooters and shared bicycles. The Annex provides case studies of the regulation of these services and identifies key lessons from this experience.