List of Android app stores
The functionality of mobile devices running the Android operating system, the most used mobile operating system globally, can be extended using "apps" – specialized software designed to offer users the means to use their devices for certain additional purposes. Such apps are compiled in the Android-native APK file format which allows easy redistribution of apps to end-users. Most apps are distributed through Google's Play Store but many alternative software repositories, or app stores, exist. Alternative app stores use the "Unknown Sources" option of Android devices to install APK files directly via the Android  Package Manager. Google Play Store. The Google Play Store (originally the Android Market), operated and developed by Google, serves as the official app store for the Android, allowing users to download apps developed with the Android software development kit (SDK) and published through Google. The store offers both free and paid apps. Apps exploiting hardware capabilities of a device can be targeted to users of devices with specific hardware components, such as a motion sensor (for motion-dependent games) or a front-facing camera (for online video calling). The Google Play store had over 50 billion app downloads in 2013  and has reached over 2.96 million apps published in 2020. Although bundled with most Android devices, the Play Store is only available on devices that are certified within the "Android Compatibility Program". As a result, manufacturers of so-called "custom ROMs", i.e.. modified versions of Android, are not allowed to bundle Google apps, including the Play Store, with their software. Compatibility can be restored by installing the Google apps from another source, such as OpenGApps, or using alternative app stores. Manufacturer app stores. In addition to some manufacturers not creating certified compatible versions of Android, some manufacturers have decided to  bundle their own app stores, either in addition to the Play Store or as a replacement. Such app stores include: Third-party app stores. App stores that do not rely on pre-installation by the manufacturer are an alternate option for finding Android applications. Apps offered through third-party app stores or websites, created by parties not affiliated with the device or operating system (OS), are also third-party apps. Such stores include: This form of app store is often used by web developers to distribute apps that are not allowed in the Google Play Store; this may be due  to an app allowing users wider access to the app-system, or offering apps for "niche users" who choose to use only free and open-source software (F-Droid) or prefer to play indie games (Itch.io). Moreover, there are alternative stores that serve to distribute "hacked" versions of paid apps, for no cost. Proxy App Store. There are also proxy app stores that act as a client for Google Play store, such as Aurora Store. Which is a fork of Yalp Store.