In order to synchronize the users, a centralized server is used, currently hosted on https://tame-occipital-sing.glitch.me. The code that the server is running is open-source (https://github.com/rafket/videosync/tree/master/server), and no state is persisted, so none of the users' data should be kept in the long term. If however there are concerns about the users' privacy, the server may be self-hosted, and the default server URL may be changed in the extension settings. In any case, the only data that is transmitted is information regarding the video being played (duration, current position, playback speed, etc.), and any URLs that are shared between the users in the same room, so no sensitive information will be transmitted in the first place.