Abstract: A system for synchronizing data across multiple browser tabs or windows includes a synchronization module and shared synchronization storage. The shared synchronization storage is local storage of the browser and is utilized by a plurality of browser windows, a plurality of tabs or a browser window and tab. The shared synchronization storage is used to store information about notifications and a timestamp as to when that information was retrieved from the notification server. The synchronization module is responsive to requests for updates from the notification client module. The synchronization module accesses the shared synchronization storage to determine whether notification information stored there is current and if so provides that notification information from the shared synchronization storage to the notification client module. If notification information stored locally is not current, the synchronization module cooperates with the notification server to retrieve current notification information.