Android Opaque Binary Blob File
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What is an OBB file?
An OBB file is an expansion file used by some Android apps distributed using the Google Play online store. It contains data that is not stored in the application's main package (.APK file), such as graphics, media files, and other large program assets. OBB files are often stored in a device's shared storage folder.
Since Google Play allows APK files to be only 100MB or smaller in file size, app developers must use expansion files to store additional app assets. Developers can create expansion files using any format they choose, such as .ZIP or .MP4, but they can also use the JOBB tool provided with the Android SDK to bundle and encrypt assets together within an OBB file.
Developers then upload these expansion files alongside their application's APK file using the Google Play Developer Console. Users who download the app receive both the app's APK file and its expansion files.
NOTE: Any additional asset provided beyond an app's APK file is called an APK Expansion File. Developers can include up to two APK Expansion Files within their Android apps.
How to open an OBB file
Typically, users should not open OBB files. OBB files store data using an encrypted format.