OpenSimulator is an open-source server platform for hosting virtual worlds. It is compatible with the client for Second Life and can host alternative worlds with differing feature sets with multiple protocols.
OpenSimulator is written in C# and is designed to be easily expanded through the use of plugin modules. OpenSimulator can operate in one of two modes: standalone or grid mode. In standalone mode, a single process handles the entire simulation. In grid mode, various aspects of the simulation are separated among multiple processes, which can exist on different machines. Standalone mode is simpler to configure, but is limited to a smaller number of users. Grid mode has the potential to scale as the number of users grows.