Open XAPK File

OBB File

OBB is short for Opaque Binary Blob and it is a file format used by Android platform to store additional apps resources and code which do not feed in the primary installation APK file. OBB file size can vary from several megabytes to multiple hundreds of megabytes. It can store graphics, sound, level information, and pretty much any other kind of resource.

Android environment supports two types of OBB types:

• Main OBB file. Supposed to be installed only once and rarely updated. Contains resources which rarely change, and which do not need to be updated with every new version of the app.
• Patch OBB file. Contain resources and another app information which can be patched frequently. Patch OBB file can change with every app update if necessary.

OBB file naming

OBB file name standard is shown below:

[main|patch]...obb

First part of the name contains type of the OBB file: main or patch. After that app expansion version and package name follow. Expansion version should match the first version of the APK file which OBB file is associated with. It means that OBB file can work with later versions of the APK file which follow the first associated version. OBB file must have .obb file extension.

OBB file storage location

After Google Play downloads OBB files they will be stored in the following location on the device:

/Android/obb/

No more than two OBB files (main and patch) can be stored in the same folder. This is either controlled by Google Play or if the app installing OBB file on its own it should also make sure that this condition is met.

OBB file download

In most cases Google Play store is responsible for downloading and saving OBB files to the device. It is possible that OBB files may be deleted by user or Google Play store is unable to download them. In such cases app has to have code which can redownload OBB files to the user device.