Abstract: This disclosure describes, in part, techniques and systems for accurately and efficiently updating applications stored on client computing devices. In some instances, the systems and techniques receive an update from an application developer, but rather than send the update directly to a client computing device that operates the application, the systems and techniques determine one or more difference between the current update and an update previously sent to the client computing device and, thereafter, send a “diff file” indicative of these differences to the client computing device. The client computing device may then use the diff file and the previously received update to re-create the new update. Thus, the systems and techniques are able to update client computing devices while limiting the amount of data sent over a network to these devices.