Before everything starts, let me clarify what USB debugging is. USB debugging is a feature opened up to developers to directly access to the Android system. With all this in mind – whether you are a going to flash a custom ROM into your Android phone, or need to root your phone to get more control authority. And here is how to enable USB debugging on different versions of Android.
How to Switch on USB Debugging Mode on Android
1 For Android 5.0 Lollipop
2 For Android OS 4.2 or later
3 For Android OS 4.0~4.1
4 For Android OS 2.X
After enabling the USB debugging, you may connect your mobile phone to computer and manage your data such as music, text messages, contacts and videos as you like.