Redsn0w is a tool that iPhone, iPad or iPod Touch users can use to remove the software restrictions imposed by Apple's operating system without losing their data. As of 2015, the tool can jailbreak almost all versions of these devices.
The iPhone Dev Team, a group of software engineers, maintains and develops Redsn0w and provides versions of the tool on its blog. Redsn0w can also run on Windows, but users must first grant it administrative privileges. Redsn0w allows users to downgrade their Apple devices to lower firmware versions, find technical information about their devices, backup files and change preferences. Advanced users can execute terminal commands and replace boot logos.