Android application package

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APK
Filename extension.apk, .xapk, .apks, .apkm
Internet media type
application/vnd.android.package-archive
Type of formatPackage format
Container forAndroid: Mobile apps
Windows 11: Desktop apps for WSA
Extended fromJAR

Android Package (APK)[1] is the Android application 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. It can be written in either Java or Kotlin.

APK files can be generated and signed from Android App Bundles.[2]

Overview[edit]

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 a tool such as Android Studio[3] or Visual 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.[4][5][6]

Most Android implementations allow 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 during the development of apps, to install apps not found on the store, or to install an older version of an existing app.[7]

Use on other operating systems[edit]

At the Windows 11 announcement event in June 2021, Microsoft showcased the new Windows Subsystem for Android (WSA) that will enable support for the Android Open Source Project (AOSP) and will allow users to run Android apps on their Windows desktop. Microsoft confirmed users will be able to sideload Android apps onto Windows and that it would be possible to install APK files downloaded from third-party sources.[8]

Package contents[edit]

An APK file is an archive that usually contains the following files and directories:

  • META-INF directory:
    • 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:
    • armeabi-v7a: compiled code for all ARMv7 and above based processors only
    • arm64-v8a: compiled code for all ARMv8 arm64 and above based processors only[9]
    • x86: compiled code for x86 processors only
    • x86_64: compiled code for x86-64 processors only
    • mips and armeabi are Deprecated since NDK r17[10][11]
  • res: the directory containing resources not compiled into resources.arsc (see below).
  • assets: a directory containing applications assets, which can be retrieved by AssetManager.
  • 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.

See also[edit]

References[edit]

  1. ^ "Application Fundamentals". Android Developers. Retrieved 2018-12-03.
  2. ^ Peters, Jay (2021-06-30). "Google is moving away from APKs on the Play Store". The Verge. Retrieved 2021-08-15.
  3. ^ "Application Studio". Android Developers.
  4. ^ "Inside the Android Application Framework" (video). Google Sites. 2008.
  5. ^ Hatem Ben Yacoub (20 April 2018). "Tips: How to install apk files on Android Emulator". Open Ha Magazine. Archived from the original on 2012-05-26. Retrieved 2021-07-17.
  6. ^ "The Structure of Android Package (APK) Files". OPhone SDN. OPhone Software Developer Network. 17 November 2010. Archived from the original on 8 February 2011.
  7. ^ "Unknown Sources: Everything you need to know!". Android Central. 27 July 2018.
  8. ^ Parmar, Mayank (2021-06-27). "Microsoft confirms Android apps will run on all Windows 11 PCs". Windows Latest. Retrieved 2021-06-28.
  9. ^ "ABI Management | Android Developers". developer.android.com. Retrieved 16 June 2018.
  10. ^ "Android ABIs | Android NDK". Android Developers. Retrieved 2020-08-14. Note: Historically the NDK supported ARMv5 (armeabi), and 32-bit and 64-bit MIPS, but support for these ABIs was removed in NDK r17.
  11. ^ 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.