USB debugging is a feature provided by Android devices once they are connected to a computer via a USB cable. It’s a mode of operation that enables and facilitates communication between an Android device and an Android software-development kit, which is used to develop various applications for the Android operating system. USB Debugging Mode lets a software developer transfer a work-in-progress application to an Android device for testing purposes.
In addition to its usefulness during the app-development process, USB debugging provides users with a system-level clearance, letting them directly access the device features through a computer. It also lets them run terminal commands through Android Debug Bridge, which can help restore devices that are completely blocked. USB debugging is sometimes necessary to fully utilize applications that require system access, such as One-Click Root.
USB Debugging Mode is turned off by default. Any application that requires the mode to be active informs the user by prompting him to enable it. In Android OS versions 4.2 and higher, the option that enables USB Debugging Mode is hidden, requiring the user to tap the Build number field in the About Phone section seven times to activate it.
It is most commonly used to install custom firmware and root the device. By rooting an Android device via USB debugging, a user gains access to its sub-systems. It allows users to replace or modify system settings and applications, whereby they can overcome artificial limitations that certain manufacturers put on their devices.