This chapter examines developments in Internet infrastructure. Attempts to measure the Internet can prove challenging, as unlike most communication technologies it relies on different actors and participants, and as a network of networks has no single point at which metrics are gathered. Nevertheless, data from surveys and databases are available for some indicators. These provide country level information on Internet infrastructure in areas such as Internet hosts, domain name registrations, address space, secure servers and network traffic, among others. The chapter also provides guidance on the interpretation of the collected data. The Internet is still growing strongly, but relative growth has decreased compared to previous periods in some categories, as might be expected given widespread adoption of this technology