APK file extension

APK (Android Application) is the only app installer extension in the Android OS. Google developed this format for adapting customized software on smartphones. The APK file contains fully compiled and ready-to-install software code.

Where is the APK file used?

Since the APK isn't a cross-platform extension, it's only supported by Android, regardless of the system version or modification. Files with this extension are stored in Google Play, the official online store. Users can also download APK files from third parties, then transfer to and install them on their smartphones. The APK file is installed manually on Android.

The APK launches the game or app installation wizard. The file has a clear structure and contains the following elements:

• Metadata (META.INF), the manifest and checksum definition files
• .LIB, the libraries used to work with different processors
• Assets and .RES, software resources
• .XML, a software code (it can be encrypted for security purposes)
• .DEX, a set of compiled classes.

The user only sees the final ready-to-install object, not the file structure. To see APK content, just open it with any archiver, such as 7Zip or WinRAR.

Software to open APK files

You need an Android device to run APK files. System users can independently download installation files to their smartphone and then open them in any explorer.

Despite extension usage limitations, the APK can be launched on Windows, macOS, and other OSs using an emulator, a software program that creates a virtual Android system machine on the user's PC. BlueStacks, Droid4X, and Genymotion are the best emulators.