Multi-platform support

Most mobile applications have multiple platform targets; the operating systems have different versions and applications need to support most of them to ensure a large user base. With Android, for example, many devices have old versions installed and do not get updated to later versions because of hardware limitations, and because manufacturers don't update their devices. At the same time, having different devices means customizing Android to suit personal taste and changing the user interface, and thus applications have to be compatible with all the different form factors and UI changes.