The APK Downloader is an extension for Chrome and Firefox web browsers that enables the direct download of application APK files from Google Play and the Amazon Appstore directly to a computer. Android applications are bundled into single files called APK files. These files on the Google Play and Amazon Appstore websites are usually only available directly to Android devices.
Whenever an Android device installs an app from Google Play or the Amazon Appstore, it downloads the application in the form of an APK file first. It then unpacks the file and installs the app. Without an external tool, these APK files are inaccessible to users, as only the Android operating system ever deals directly with them.
Users often want to install apps onto Android devices that don't have access directly to the app stores where the apps are available. This access can be granted by using the APK Downloader extension to download the APK file to a computer and then transferring the file manually from the computer to the Android device through email, USB or a wireless transfer.
While the APK Downloader extension is easy to use, it is unclear whether or not it violates the Amazon Appstore or Google Play terms of service. The author of the APK Downloader extension notes this prominently on the APK Downloader web page and suggests that all potential users of the extension review the terms of service for Google Play and the Amazon Appstore before using it.