Mirror
#1 Open Source Unity Networking Library
...It was originally based on UNET and has evolved into a stable, modular framework used by many production Unity projects. The library is designed to make multiplayer development easier by handling common networking patterns such as network identities, synchronization, remote procedure calls, authority, spawning, and transport integration. Mirror supports multiple low-level transports, making it adaptable to different game genres and deployment needs. It is suitable for small multiplayer games, cooperative games, competitive prototypes, and even larger persistent-world or MMORPG-style projects. ...