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apk (file format)

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This article is about the Android package format. For the Alpine Linux package format, see Alpine Linux.
APK
Filename extension.apk, .apks, .aab, .xapk, .apkm
Internet media type
application/vnd.android.package-archive
Type of formatPackage format
Container for
Extended fromJAR

The Android Package with the file extension apk[1] is the 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

APK is analogous to other software packages such as APPX in Microsoft Windows, .app on HAP for HarmonyOS 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

Blackberry Limited supported Android 4.1 Jelly Bean apps and up through Android Runtime to now discontinued Blackberry 10 through the January 2014 10.2.1 firmware update.[8] On June 18, 2014, BlackBerry announced an official relationship with Amazon.com, which resulted in the 10.3 update bundling the Amazon Appstore.

At 2015 Build, Microsoft had also announced an Android runtime environment for Windows 10 Mobile known as "Astoria", which would allow Android apps to run in an emulated environment with minimal changes, and have access to Microsoft platform APIs such as Bing Maps and Xbox Live as nearly drop-in replacements for equivalent Google Mobile Services. Google Mobile Services and certain core APIs would not be available, and apps with "deep integration into background tasks" were said to poorly support the environment.[9][10]

On February 25, 2016, after already having delayed it in November 2015,[11][12] Microsoft announced that "Astoria" would be shelved, arguing that it was redundant to the native Windows Bridge toolkit since iOS is already a primary target for mobile app development. The company also encouraged use of products from Xamarin (which they had acquired the previous day) for multi-platform app development using C# programming language instead.[13][14] Portions of Astoria were used as a basis for the Windows Subsystem for Linux (WSL) platform on the PC version of Windows 10.[15]

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.[16]

Users were not able to use WSA when the OS launched, but it is currently[when?] being tested with Windows Insiders in the United States, for a global release sometime in 2022. [citation needed]

Huawei released its proprietary operating system HarmonyOS on August 9, 2019, for smart TVs first and later launched for phones and tablets on June 2, 2021, with HarmonyOS 2.0. HarmonyOS under the Linux module of the multi-kernel designed system is compatible with legacy Android apps under the Ark Compiler under the new IoT smart oriented operating system for phones and tablets. It is claimed by the company to improve Android system operation fluency by 24%, response speed by 44%, and the smoothness of the third-party application up to 60%. Furthermore, the Android system optimized with Ark compiler is close to Apple's iOS terminology. However, an open source HarmonyOS module built for embedded smart devices, OpenHarmony is not compatible with Android apps.[17]

JingOS developers released JingOS that claims to be “the world’s first iPadOS-style Linux distro”. The tablet-friendly Linux distro was launched in March 2021. It can run both Linux apps and Android apps. It is adapted to run naturally with touch screen, stylus, keyboard, and trackpad natively making it a ‘convergent’ Linux OS.[18]

WayDroid is a containerized approach rewritten from Anbox container to get an Android environment running in a Linux system with the added advantage of full hardware access. The container lets you run Android apps on Linux-based phones such as Ubuntu Touch, PostmarketOS via a Linux terminal, however not all Linux-based operating systems are supported. The open source software container basically puts a complete Android operating system into a container that can run on Linux devices, allowing users to install APK files and run Android apps from a Linux host environment.[citation needed]

On September 13, 2021, Huawei launched their own App Engine solution in their 1+8N ecosystem that enables Android apps and games from Huawei's AppGallery to be run on Huawei PCs and laptops. With this plugin, you can download and play apps and games directly on your Huawei pc device. You can access these apps via Huawei AppGallery smartphone apps on a large screen. Huawei App Engine supports Multi-window mode, you can run multiple Android apps at once on the same screen. The surprising element of this news includes the support of running and installing APK files directly from the file explorer.[19]

Google plans to introduce its own way to run Android apps on Windows in 2022.[20]

Package contents

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[21]
    • x86: compiled code for x86 processors only
    • x86_64: compiled code for x86-64 processors only
    • mips and armeabi, deprecated since NDK r17[22][23]
  • 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 M, or Androguard.
  • classes.dex: The classes compiled in the dex file format executed by Android Runtime (or by Dalvik virtual machine used in Android 4.4 KitKat).
  • resources.arsc: a file containing precompiled resources, such as binary XML for example.

See also

References

  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 2012-05-21. 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. ^ Michael, Kozlowski. "BlackBerry 10.2.1 Update Allows you to Install APK Files on your Phone". GoodEReader. GoodEReader. Retrieved January 29, 2014.
  9. ^ "How will Android support work in Windows 10 for Phones?". TechRadar Pro. Archived from the original on May 19, 2015. Retrieved May 22, 2015.
  10. ^ "Microsoft brings Android, iOS apps to Windows 10". Ars Technica. April 29, 2015. Retrieved April 30, 2015.
  11. ^ "Microsoft might not bring Android apps to Windows after all". The Verge. Vox Media. November 16, 2015. Retrieved November 16, 2015.
  12. ^ Collins, Katie (November 16, 2015). "Microsoft presses pause on tool for porting Android apps to Windows 10". CNET. CBS Interactive.
  13. ^ "Microsoft confirms: Android-on-Windows Astoria tech is gone". Ars Technica. Conde Nast. February 25, 2016. Retrieved February 25, 2016.
  14. ^ "An Update on the Developer Opportunity and Windows 10". Building Apps for Windows blog. Microsoft. February 25, 2016. Retrieved February 25, 2016.
  15. ^ Bright, Peter (April 6, 2016). "Why Microsoft needed to make Windows run Linux software". Ars Technica. Condé Nast.
  16. ^ Parmar, Mayank (2021-06-27). "Microsoft confirms Android apps will run on all Windows 11 PCs". Windows Latest. Retrieved 2021-06-28.
  17. ^ Amy, Sarkar. "ARK Compiler: Huawei's self-developed Android application compiler – Explained". HC Newsroom. HC Newsroom. Retrieved April 28, 2019.
  18. ^ Sneddon, Joey. "First Look: Meet the New Linux Distro Inspired by the iPad". omg!ubuntu!. omg!ubuntu!. Retrieved 1 February 2021.
  19. ^ Li, Deng. "Huawei Mobile App Engine launched, run Android apps and games on PC". HC Newsroom. HC Newsroom. Retrieved September 13, 2021.
  20. ^ Warren, Tom (2021-12-09). "Google is bringing Android games to Windows in 2022". The Verge. Retrieved 2021-12-13.
  21. ^ "ABI Management | Android Developers". developer.android.com. Retrieved 16 June 2018.
  22. ^ "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.
  23. ^ 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.
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