BA2 (Fallout 4 / 76) file format

.ba2 · archive (game asset bundle) · introduced 2015 by Bethesda Softworks

What is a BA2 (Fallout 4 / 76) file?

BA2 is the successor to BSA, introduced with Fallout 4 in 2015. It separates general-purpose data, textures, and DDS data into distinct sub-formats with their own optimized layouts, dramatically speeding up streaming of high-resolution textures. Fallout 76 added LZ4 compression on top.

Most readers reach this page after double-clicking a .ba2 file and finding their operating system unsure what to do with it. The good news: BA2 (Fallout 4 / 76) is a well-understood format with mature tooling on every major platform. It is supported in one click by mainstream archivers on Windows, macOS, and Linux.

How to extract a BA2 (Fallout 4 / 76) file

Opening a .ba2 file is straightforward on every modern operating system. The exact steps depend on which platform you are on:

On Windows

Locate the .ba2 file in File Explorer.
Right-click the file. If you have 7-Zip installed, choose 7-Zip → Extract Here. On Windows 11 the built-in extractor handles ZIP, 7z, RAR and several other formats directly through Extract All…
If prompted, pick a destination folder and click Extract.
The extracted files appear in a folder next to the original archive.

On macOS

Find the .ba2 file in Finder.
Install The Unarchiver from the Mac App Store, or Keka for both creating and extracting.
Right-click the file → Open With → The Unarchiver (or just double-click after Unarchiver is set as the default).
The extracted folder appears next to the archive.

On Linux

Use your file manager: right-click the archive → Extract Here (file-roller on GNOME, Ark on KDE).

On the command line, run one of:

7z x archive.ba2    # works for almost any format

The files appear in the current directory.

How to create a BA2 (Fallout 4 / 76) file

To pack files into a .ba2 archive, you typically need an archiver that supports writing this format. Not every tool can create every format — for example, only WinRAR can create real RAR files. The sidebar lists the software known to read and write BA2 (Fallout 4 / 76).

On the command line, the canonical create command is:

# Use 7-Zip, PeaZip, or the format's reference tool to create .ba2 files.

If you regularly create archives at scale, a dedicated archive automation suite can wrap this command in scheduled jobs, integrity checks, and offsite replication.

Strengths

Fast texture streaming
LZ4 in newer revisions

Weaknesses and limitations

Bethesda-specific
Format revisions break older tools

Typical use cases

Fallout 4 and Fallout 76
Starfield modding

Technical details

BA2 (Fallout 4 / 76) uses the zlib + LZ4 (Fallout 76) algorithm and is identified on disk by the magic byte sequence 42 54 44 58. The standard MIME type is application/x-bethesda-ba2. The format is an open specification and is free for any use.

Frequently asked questions

Is BA2 (Fallout 4 / 76) safe to open?

Archive files are containers — they are only as safe as what they contain. A .ba2 from a trusted source is fine; one received from a stranger can hold malicious executables, scripts, or files engineered to exploit bugs in your archiver. Always keep your archiver updated, and never run unknown executables that come out of an archive. A safe workflow is to extract into a sandbox and scan the contents before opening anything.

What is the maximum file size?

Modern implementations support archives in the multi-terabyte range. The practical limit is your filesystem (FAT32 caps at 4 GB; ext4, NTFS, APFS, and exFAT all comfortably handle multi-TB files).

Can I password-protect a BA2 (Fallout 4 / 76)?

Some archivers can wrap BA2 (Fallout 4 / 76) files in an encrypted container, but the format itself does not always include built-in encryption. Check your archiver's documentation.

How does BA2 (Fallout 4 / 76) compare to other formats?

See our format comparison pages such as ZIP vs 7z, ZIP vs RAR, and tar.gz vs tar.xz for side-by-side feature tables.