The Unity Multiplayer SDK uses Sessions as a comprehensive wrapper to simplify the integration of Unity Gaming Services (UGS) backend features, such as Lobby, Relay, and Matchmaker into multiplayer games. This single interface reduces boilerplate code and standardizes UGS usage, automatically managing features like Lobby heartbeating and, when enabled, the Lobby/Relay integration, allowing developers to focus on unique game features.

The following table compares the high level view for P2P Matchmaking when using Matchmaker, Lobby, and Relay individually versus using the Sessions API.

The following standalone SDKs are depreacted:

The standalone SDKs are deprecated in favor of , their functionalities are still accessible within . Upgrade to the Multiplayer Services SDK by following the migration guide.

Starting with version of , you can now choose when to start the network connection in your game flow. This isn't available with Matchmaking.

If you make the host use , or when creating the session, then the network starts automatically as soon as the session is created. Any player joining this same session is pulled into the network connection automatically.

If you don't make the host use , or when creating the session, then no network connection is automatically established. You can then execute any pre-match setup such as choosing a character or waiting for all players to be ready before establishing the network connection. No network is created for any player joining this session at that point. When the host is ready, they can use , or to start the network. Any player joining this session after the network start is pulled into the network connection automatically.

The Multiplayer SDK supports the WebGL target, however, User Datagram Protocol isn't supported for this platform, consequently, Quality of service isn't available, neither is the Datagram Transport Layer Security encryption protocol for Relay. Broader limitations remain, even those unrelated to the Multiplayer SDK, such as restrictions on multithreading including the use of .

The Session API wraps multiple services into a single SDK. This includes Relay, Distributed Authority, Lobby, and Matchmaker and therefore contributes to the billing of each of those services.

Refer to the Unity Gaming Services pricing page for complete details.

Set the scriptable define under Script Compilation in the Player window of the Untiy Editor.

Quality of service (QoS) measurements are automatically used in the Sessions API when a player calls .