Can Apple Apps Be Used on the iPhone & iPad?

App Sharing

Sharing games and apps on all devices linked to your iTunes account is much like buying a DVD and having friends or family over to watch it with you. You aren't all expected to own a copy of the DVD just so you can watch it -- one purchase is sufficient. Similarly, any devices you sign into your iTunes account can download and use apps purchased on any other device without incurring additional charges. A device can only be signed into one iTunes account at a time, however, and cannot transfer content between accounts.

Many games and apps are considered "universal," which means they contain data and visuals that allow the app to run natively on all Apple devices. For example, the iPad's screen is a different ratio and size to the iPhone, requiring different graphics files within the same app. The iPad is able to load the majority of iPhone applications, as long as those apps don't require GPS or cellular data connections to operate, as some models of the iPad lack the necessary hardware. The iPhone cannot run iPad-only apps.

When loading an iPhone game or app onto the iPad, it will appear at the iPhone's native resolution in the center of the iPad's screen. To help with controls and visibility, the iPad can automatically "upscale" the image, which doubles its size to better fill the iPad's screen. This does not improve the resolution, however, which merely has its pixel size doubled to account for the larger display size. A button is provided in the corner of the iPad's screen for changing between a standard and upscaled display when running iPhone apps.

You can check for games and apps purchased by other devices on your iTunes account by launching the App Store application on your iPhone or iPad, and tapping the "Updates" button followed by the "Purchased" button. A list of available, previously purchased apps that can be downloaded is displayed. Tapping the cloud button next to each app will download it to your iPhone or iPad, without incurring any charges. If an app is not compatible -- for example, iPad-only apps cannot be run on the iPhone -- it will not be displayed in the "Purchased" list.