Virtual reality applications allow users to immerse themselves in a virtual world and interact with it. When a head-mounted display is used as the output medium, the user can fully dive into the virtual world. To make this virtual world accessible to multiple users, synchronization of the applications is necessary. This book develops an application that provides basic functions for synchronizing actions in the virtual world and interactions between users. It discusses the fundamentals and analyzes and evaluates the available technologies. It defines the conditions that must be met to achieve a high level of immersion. Using the selected hardware and software, a prototype is developed to investigate the latencies that occur during synchronization over the network. It turns out that a very low latency of 40 ms can be maintained when synchronizing up to three users. An increase in latencies is not expected even with a higher number of users.