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uid: arkit-participant-tracking
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# Participant tracking

A participant represents another device in a multi-user collaborative session. Although you can start and stop the participant subsystem at any time, the session must receive `ARCollaborationData` from other peers in the multi-user session in order for participants to be detected. For an example implementation, see the [ARCollaborationData sample on GitHub](https://github.com/Unity-Technologies/arfoundation-samples/tree/master/Assets/Scenes/ARCollaborationData).