iOS jailbreaking, or simply jailbreaking, is the process of removing the limitations imposed by Apple on devices running the iOS operating system through use of custom kernels. Such devices include the iPhone, iPod Touch, iPad, and 2nd Gen Apple TV. Jailbreaking allows users to gain full access (or root access) to the operating system, allowing iOS users to download additional applications, extensions, and themes that are unavailable through the official Apple App Store, via installers such as Cydia. A jailbroken iPhone, iPod Touch, or iPad running iOS can still use the App Store, iTunes, and other normal functions, such as making telephone calls. Unlike rooting an Android device, jailbreaking is
necessary if the user intends to run software not authorized by Apple.
At its core, jailbreaking an Apple iOS device gives access to its root filesystem, allowing modification and installing third-party software components. This gives the user more control over the device and may enable features that were previously unavailable. In many cases, jailbreaking also voids the device’s warranty.
Under the DMCA of 2010, jailbreaking Apple iDevices is legal in the United States, although Apple has announced that the practice “can void the warranty.” However, the jailbreaking process does not include any modification to the hardware, so it can be quickly and easily reversed simply by restoring the operating system through iTunes.