One of the primary benefits claimed for smart client applications is support for offline use-users can take a snapshot of data while connected to a data source and change it while disconnected from the source. Offline capabilities are attractive for supporting mobile users with devices such as laptops and users with intermittent or unreliable network connections. However, supporting these capabilities is not simple.

Most IT applications are not just giant repositories of data; to ensure the integrity of that data, they also include rules (business logic) that specify what operations may be performed on that data and validate changes as they are made. An accounts payable system, for example, might require that a purchase order be opened and approved before a payment is entered. Online applications (applications in which the end user is constantly connected to the back-end data stores) typically validate any changes to data against these rules and immediately inform the user if the update is rejected, presenting an opportunity to correct the error.