Cyberspace is no different from traditional cities, at least in economic terms. Urban economics governs the creation of new space on the Internet and explains location choices and price gradients in virtual space. This study explores registration dynamics in the largest primary market for virtual space: Internet domain names. After developing a framework for domain registrations, it empirically tests whether domain registrations are constrained by the depletion of unregistered high quality domain names. Estimations based on registrations of COM domain names suggest that the number of domains expands substantially slower than the growth in overall demand for domain space. Supplying alternative domain extensions can relax the shortage in domains in the short term.