Facebook added the ability for application developers to determine which devices users are accessing their apps from.
The more information developers have to work with, the better, and the data on devices will enable them to tailor users’ experiences with the apps to their devices.
Facebook said in a post on its developer blog:
To optimize the experience across mobile devices, developers can now find out which devices their users have. Querying the /user edge of the graph API for the device field returns the device or devices used by that person. Using this information, you can improve the mobile app or game experience for users in many ways, such as prompting a Web user with an iPhone to install your native app or offering a user to invite their friends with devices supported by your mobile app. Check out the multi-friend selector documentation to learn more about implementing this feature.