mainversionpackageobb

Mainversionpackageobb is an informal term used to describe the naming pattern for Android APK Expansion Files in the OBB format. Android apps that exceed the 100 MB APK limit can include large assets in separate OBB files downloaded after installation. The main OBB contains the primary expansion data, while a patch OBB can contain incremental updates. The term combines the components: main (type), versionCode (version), package (application package name), and obb (file extension).

Naming convention: The main expansion file is named main.[versionCode].[packageName].obb. An optional patch file is patch.[versionCode].[packageName].obb. VersionCode is the APK version code assigned by the Play Console; packageName is the app’s package name, such as com.example.app. The files are stored on the device in the Android/obb/ directory under the corresponding package folder. The main and patch distinctions indicate how the data should be applied by the app, with the main file loaded first and the patch applied on top if present.

Usage and access: During app install or first run, Google Play downloads the expansion files to the device. Apps use the APK Expansion Library to verify, download (if needed), and access the content without needing to unzip the entire archive. Access is performed through the app’s code, which opens assets within the OBB as if they were part of the app’s external storage.

Evolution and alternatives: The concept remains relevant for legacy apps. Google now promotes Play Asset Delivery as a more flexible system for delivering large assets. It supports on-demand delivery, reduced initial download sizes, and more granular updates, but the OBB expansion approach remains documented and supported for apps that rely on it.