Methods and systems are provided for implementing session synchronization to synchronize applications at different user systems (e.g., mobile device, laptop, desktop, tablet) of a particular user. This platform level solution can maintain session information received any number of different user systems of the particular user and share this collective session information with each of the other user systems as session-synchronization information that can be used, at any user system of that user, to ensure that when that user switches from using one user system to another user system that applications at the “new” user system being switched to are synchronized with any other applications that were most recently in use at all of the other user systems of that user.