You may have spotted an option called "USB debugging" on your Android device when flipping through the device's "Settings" menu, but unless you're a developer, you'll probably never have a use for this feature. USB debugging is an essential development feature that lets programmers transfer apps from an Android development kit on a computer to an Android phone or tablet for testing. Users typically install apps through the Google Play Store or another marketplace; USB debugging lets developers test an app on an actual device without having to list the in-progress app in an app store.
Troubleshooting in the Development Process
Mistakes are inevitable when programming. Sometimes a developer does something simple like typing the wrong character or inserting the wrong command; other times the developer makes substantial errors in the code. Instead of writing an Android app from start to finish and hoping for the best, the developer can use debugging programs to check for syntax errors. Android developers can test in-progress programs on computer-emulated Android devices and on Android devices themselves.
Real World Testing
Developers use Android USB debugging to test apps in a real-world setting on a physical Android device. Being able to transfer an in-development app to a physical Android device can expedite the development process. A developer can compile an app with the development kit and install it on an Android device via USB debugging. Instead of just looking at app code, USB debugging lets a developer play around with the app on a physical device during the development process. USB debugging helps the developer understand how the user interface will perform in real-life conditions. Additionally, testing on a physical device can identify hardware compatibility and performance issues. Using an actual device is the only way to test some hardware features like the accelerometer.
The Emulation Alternative
The Android Software Development Kit offers a robust mobile device emulator that runs on a computer. The Android emulator is used to create virtual devices to give the developer an idea of how well an app will work on an actual device. The emulator can test for compatibility issues with devices and device features to which the developer doesn't have access. However, emulation can be demanding on hardware, which may not be able to run virtual devices at real-world speeds.
Enabling USB Debugging
The process to enable USB debugging is different depending on your device's Android version. USB debugging is hidden on Android 4.2 and later devices by default; you can reveal the option by going to "Settings," selecting "About phone" and tapping "Build number" seven times. You can turn on USB debugging on Android 4.0 and later by opening "Settings," selecting "Developer Options" and checking the box next to "USB debugging." You can enable USB debugging on Android 2.x-3.x devices by opening "Settings," selecting "Applications," tapping "Development" and checking the box next to "USB debugging."