Android Package (APK) is a package file intended for the Android operating system. It is an acronym for the English word Android Application Pack.

It can be compared to proprietary Windows software installation files such as .exe or .msi. It turns out that the APK has a format similar to compression that is made by ZIP, and inside it are all the files needed for the installation of apps and games. To create an APK file steam guard, the entire source code of the application is compiled and then packaged into a single file, using tools such as the aapt program, dx.bat (found in the Android SDK), javac, used in compiling the java classes present in source code, and other specific programs. The APK is a ZIP compression format based on the JAR format.

The APK can either be officially obtained from the Google Play virtual store or downloaded from third-party sites, or even after developing the application in an Integrated Development Environment (IDE) such as Android Studio or the Android Development Kit (SDK) via Command Line. If the APK is downloaded on third-party sites, the installation is done simply by clicking on the downloaded .apk file on the Android smartphone. Already for the developers the installation is done automatically in the Android emulator. If the developer wants to test the application on the smartphone, use the debugging program adb (Android Debugger). They are also found installed natively in the system, are popularly called «Native Apps» such as: clock, calendar, phone, contacts, etc.