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What is an APK? A Comprehensive Guide to Android App Files

If you’re a regular reader of sites, like Trusted Reviews, or like to tinker with your smartphone, you may have come across the term APK. But what does it mean and why is it important?

In a nutshell, Android apps are often distributed as a package file type known as an APK (short for Android Application Package).

An APK is essentially the app itself, packaged together with all of its assets and code. They are used as a means to streamline getting an app onto your phone or tablet.

Rather than having to sideload the app from some random website, Google allows developers to upload their APKs directly to their developer console. That way, you can download and install it directly on your phone or tablet instead of having to go through that process every time you want to update it.

Still got questions? Keep reading to learn more.

The APK File

APK is a file type, like an MSI for Windows or an DMG for Mac, that contains the code and resources for Android apps. It’s often referred to as an app, but it’s actually more like a container for an app. That’s because it contains all of the resources, permissions, and code needed to install and run an app.

As such, it’s helpful to think of it like a zipped folder that you can extract and view the contents of. When you download an Android app from the Google Play Store, you’re actually downloading an APK file. Once you’ve installed the app, you can view the contents of the APK file by opening it in a file manager app or by decompiling the app using an APK analyzer.

What’s Inside an APK?

An APK is a compressed folder that contains the app’s code, assets, etc. In the folder, you’ll find one or more files along with other folders. Let’s look at a few of those files:

  • APK file: This is the actual APK file you’ve downloaded from the Play Store. It’s an executable file that contains the app’s code. The app’s name is also included in the file’s name.
  • AndroidManifest.xml: This is where you’ll find details about the app, including its name, version number, dependencies, functionality, etc. The manifest is critical to installing and running the app. If this file is missing or corrupt, the app won’t install or run properly.
  • assets: This folder contains all of the assets used by the app, including images, videos, fonts, and other files.
  • lib: This folder contains the app’s code, which is written in Java. You may also see folders named after Java packages like com, java, etc.
  • res: This folder contains the app’s resources. These include design assets like icons, graphics, and other visual elements.

APK Limitations

There are a few limitations of APK files that you need to be aware of before installing apps from outside the Play Store. APKs are signed using a private key. If they’re not signed with a certificate, they can’t be installed on devices that aren’t owned by the developer.

You also can’t install an APK on a device running a different Android version to the one it’s intended for. This means that if you want to install an app on a device running Android 4.0, the app’s APK must have been built for Android 4.0.

Apps installed via an APK won’t receive automatic upgrades like those installed from the Play Store. You’ll have to manually update the app to make sure that it stays secure and functional.

Unless you’re a professional looking to install proprietary software, or a developer testing a new app, we recommend most users avoid installing apps from outside the Play, or another big name, app store.

Many from less scrupulous sources can contain malware. In some instances, since the software may not be optimised to run on the exact version of Android you’re using they can also cause performance issues.

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