bzip3 file format

.bz3 · compression (single file) · introduced 2022 by Kamila Szewczyk

What is a bzip3 file?

bzip3 is a modern reincarnation of bzip2, released in 2022 by Kamila Szewczyk. It uses the Burrows-Wheeler transform like its namesake but pairs it with arithmetic coding and modern SIMD-friendly code, achieving substantially better compression than bzip2 at roughly the same speed. Adoption is still niche but growing in the Linux package world.

Most readers reach this page after double-clicking a .bz3 file and finding their operating system unsure what to do with it. The good news: bzip3 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 bzip3 file

Opening a .bz3 file is straightforward on every modern operating system. The exact steps depend on which platform you are on:

On Windows

Locate the .bz3 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 .bz3 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.bz3    # works for almost any format

The files appear in the current directory.

How to create a bzip3 file

To pack files into a .bz3 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 bzip3.

On the command line, the canonical create command is:

# Use 7-Zip, PeaZip, or the format's reference tool to create .bz3 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

Better ratio than bzip2
Open source
Block-based for parallelism

Weaknesses and limitations

Very new — limited tool support
Memory hungry

Typical use cases

Source archives where bzip2 was traditional
High-ratio scientific data dumps

Technical details

bzip3 uses the Burrows-Wheeler + run-length + arithmetic coding algorithm and is identified on disk by the magic byte sequence 42 5A 33 76. The standard MIME type is application/x-bzip3. The format is an open specification and is free for any use.

Frequently asked questions

Is bzip3 safe to open?

Archive files are containers — they are only as safe as what they contain. A .bz3 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 bzip3?

Some archivers can wrap bzip3 files in an encrypted container, but the format itself does not always include built-in encryption. Check your archiver's documentation.

How does bzip3 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.