The Chinese hacker group Taig has released an untethered jailbreak tool for Windows that allows iPhones and iPads be cracked with iOS 8.3. There is no jailbreak tool for users running OS X.
Taig, which delivered more jailbreaks, states that before a jailbreak can be done a backup must be made on an iOS device via iTunes or iCloud. The hackers warn that some plug-ins after the jailbreak still not work because the Cydia Subtrate component has not yet been made compatible with iOS 8.2 and 8.3. Whether there will be also an OS X version is not entirely clear.
The jailbreak allows you to install software from third-party on iOS 8.3 devices not authorized by Apple. Through Cydia, users can install among other tweaks, mods, themes, and apps by downloading packages.