Android application package
Android Package (APK) is the package file format used by the Android operating system, and a number of other Android-based operating systems for distribution and installation of mobile apps, mobile games and middleware.
|Internet media type|
|Type of format||Package format|
|Container for||Mobile apps|
APK is analogous to other software packages such as APPX in Microsoft Windows or a Debian package in Debian-based operating systems. To make an APK file, a program for Android is first compiled using Android Studio, and then all of its parts are packaged into one container file. An APK file contains all of a program's code (such as .dex files), resources, assets, certificates, and manifest file. As is the case with many file formats, APK files can have any name needed, but it may be required that the file name ends in the file extension for being recognized as such.
The Android system allows users to manually install APK files only after they turn on an "Unknown Sources" setting that allows installation from sources other than trusted ones like Google Play. One may do so for many reasons, such as to install apps not found on the store, or to install an older version. Although one can downgrade an app this way by uninstalling the new version first, doing it via Android Debug Bridge is better as it allows for keeping data.
An APK file is an archive that usually contains the following files and directories:
MANIFEST.MF: the Manifest file
- The certificate of the application.
CERT.SF: The list of resources and a SHA-1 digest of the corresponding lines in the MANIFEST.MF file; for example:
Signature-Version: 1.0 Created-By: 1.0 (Android) SHA1-Digest-Manifest: wxqnEAI0UA5nO5QJ8CGMwjkGGWE= ... Name: res/layout/exchange_component_back_bottom.xml SHA1-Digest: eACjMjESj7Zkf0cBFTZ0nqWrt7w= Name: res/drawable-hdpi/icon.png SHA1-Digest: DGEqylP8W0n0iV/ZzBx3MW0WGCA=
lib: the directory containing the compiled code that is platform dependent; the directory is split into more directories within it:
res: the directory containing resources not compiled into resources.arsc (see below).
assets: a directory containing applications assets, which can be retrieved by
AndroidManifest.xml: An additional Android manifest file, describing the name, version, access rights, referenced library files for the application. This file may be in Android binary XML that can be converted into human-readable plaintext XML with tools such as AXMLPrinter2, apktool, or Androguard.
classes.dex: The classes compiled in the dex file format understandable by the Dalvik virtual machine and by the Android Runtime.
resources.arsc: a file containing precompiled resources, such as binary XML for example.
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Note: Historically the NDK supported ARMv5 (armeabi), and 32-bit and 64-bit MIPS, but support for these ABIs was removed in NDK r17.
- Dan, Albert (Sep 5, 2018). "Changelog r17". GitHub. Retrieved 2020-08-14.
Support for ARMv5 (armeabi), MIPS, and MIPS64 has been removed. Attempting to build any of these ABIs will result in an error.