Mirror is a system for building multiplayer capabilities for Unity games. It is built on top of the lower level transport real-time communication layer, and handles many of the common tasks that are required for multiplayer games. While the transport layer supports any kind of network topology, Mirror is a server authoritative system; although it allows one of the participants to be a client and the server at the same time, so no dedicated server process is required. Working in conjunction with the internet services, this allows multiplayer games to be played over the internet with little work from developers.

Mirror is focused on ease of use and iterative development and provides useful functionality for multiplayer games.