An APK (Android Package) file is the installer format used for the Android operating system. When you "download an APK," you are manually retrieving the app's components to install them outside of the standard Google Play Store.
: This is a highly-rated open-source app that provides a detailed report on both installed apps and .apk files stored on your device. It decodes metadata like AndroidManifest.xml and lists all requested permissions. Download App apk
: For developers, this built-in tool in Android Studio allows you to view file sizes, navigate the ZIP hierarchy of the APK, and estimate download sizes. An APK (Android Package) file is the installer