Synchronization of data accessible by an application program is performed transparent to the application program. After a data item is instantiated by the application program, the synchronization engine performs data synchronization without or with minimal intervention of the application program. The synchronization engine may be part of an operating system. The synchronization engine is preinstalled on a computing device; therefore, application program developers can simply define whether the data items associated with the application programs should be syncable, and if so, to what extent the data items should be syncable. The application program developer is relieved of the task of developing the synchronization engine or other software components associated with data synchronization.