All about OBB Files

The OBB file type is primarily associated with Android Studio.

OBB	File extension: OBB
	File type:	encrypted data archive

What is an OBB file?

OBB files mostly belong to Android Studio by Google. OBB files are expansion files used by android applications to store additional data that that would exceed the size limit of the main APK file.

• Naming: The name "Opaque Binary Blob" is used in computer science to refer to a sizeable piece of data, which looks like binary garbage to entities that do not know that the blob carries, but makes sense to entities that have proper access permissions.
• Usage: Play Store has a requirement that the compressed APK file that a user downloads must not exceed 100MB (Megabytes). While this is enough for most applications, some use high-fidelity graphics, media files, and other assets which far exceed the size limit. For this reason, Google has allowed android developers to attach two large expansion files to their applications. These expansion files can be any format (like ZIP, PDF, MP4, etc..), but are most often OBB files created using the JOBB development tool.
• Structure: OBB files are are an encapsulated and encrypted set of resource files and subsequent patches for that set. These resource files can be anything the developer deems necessary for their application, like graphics, media, textures, etc. These expansion files have a limit of maximum 2 per APK file, and a maximum size of 2GB.

How to open an OBB file

You need a suitable software like Android Studio from Google to open an OBB file. Without proper software you will receive a Windows message "How do you want to open this file?" or "Windows cannot open this file" or a similar Mac/iPhone/Android alert. If you cannot open your OBB file correctly, try to right-click or long-press the file. Then click "Open with" and choose an application. You can also display a OBB file directly in the browser:. Just drag the file onto this browser window and drop it.

Online OBB Text Viewer

Choose your .obb file to analyze

or drag and drop it here

Online File Viewer

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OBB file format:

Every file has a defined file format, i.e. how the data is arranged in the file. The initial characters of a file are called signature, sometimes also referred to as "magic bytes". The signature can be used to infer the file format. However, different programs can use the same file extension, and file extensions can be assigned incorrectly. If there are problems opening a file, you must first determine the file format used. Below is our analysis of the OBB files:

OBB is a very widely used file extension. The file type predominantly uses a uniform format. The two most popular formats are as follows:

• 70% of all OBB files internally use the ZIP format, multiple files are compressed and combined into one OBB file. Most often they are 4 to 190 compressed files. Tip: If you rename the file ending to .zip and then double-click it, you see the included files and images. The average file size is 600 MB with most files being between 100 MB and 1 GB in size. The keywords assets and Data are typical for these files. These files are often associated with tencent, pubg, freefireth, krmobile, rockstargames, imobile, android and patch.
• 3% of all OBB files use the same file format, which can be identified by the letters "1bsr" at the beginning. If you open these files in a text editor, you will see only illegible characters. Most of these files are 630 MB to 710 MB in size. The keywords 1bsr are typical for these files. The following filename is common: main.337.com.ea.game.pvz2_ecl.obb or main.524.com.ea.game.pvz2_row.obb. Such OBB files store data about game.

All other OBB files (27%) have different formats, often e.g. UnityFS, GZIP, SQL, fat, CPK, KPX, OBB, fmf, NCTT, AndroidOBB and WBND. Sometimes used for konami, pesam, shooter, firsttouchgames, activision or callofduty. If you want to find out what your OBB file contains, drag and drop it onto this page.