lbzip2, parallel bzip2 compression utility

Fork notice. This is a fork of kjn/lbzip2, created on 2026-08-17 from upstream commit 724352c, because upstream is unmaintained -- Homebrew disabled its lbzip2 formula on 2025-07-07 for that reason and removed it on 2026-07-08. Changes made in this fork are described in CHANGES.md and recorded in the git history. It remains free software under the GNU General Public License, version 3 or later; see COPYING.

Copyright (C) 2011, 2012, 2013, 2014, 2015 Mikolaj Izdebski
Copyright (C) 2008, 2009, 2010 Laszlo Ersek

This README file is part of lbzip2 version 2.6.5.

lbzip2 is a parallel, SMP-based, bzip2-compatible compression utility.

lbzip2 compresses and decompresses files using a variation of BWT compression stack. More information on this topic can be found in the ALGORITHM file.

How this fork differs from upstream

The compressed format is untouched: this produces and reads exactly the same bytes as upstream and as bzip2.

• Faster decompression — 7 to 10%. The inverse MTF transform uses a single vector shuffle (vqtbl1q_u8 on AArch64, pshufb on SSSE3) instead of a branch the predictor cannot learn. No compiler flags change, so a default build stays as portable as it was. (kjn/lbzip2#31)
• A default build is optimised again. A plain cmake .. selected no build type and therefore no optimisation at all, making the binary roughly twice as slow as the autotools build it replaced. (kjn/lbzip2#39)
• Builds and passes its tests on Windows, under the MSYS2 runtime — open upstream since 2016. Native Win32 is still unported. (kjn/lbzip2#16)
• Builds and passes its tests on macOS, which strict POSIX feature-test macros had broken outright.
• Tested on four platforms — glibc Linux, musl Linux, macOS on Apple Silicon, and Windows — on every push, all 1111 cases. Upstream CI covered Linux alone.
• make install installs something: the binary and all three manual pages, honouring --prefix and DESTDIR. It previously installed nothing.
• Installable with Homebrew from a tap, and reports its own version and project page correctly.

CHANGES.md describes each of these in detail.

Speed against the last official release

lbzip2 2.5 is the last release upstream made, in 2015, and is what most installed copies are. Against it, this version compresses about 8% faster and decompresses about 9% faster. Medians of nine alternating runs over 220 MB of mixed real data -- C source, manual pages, shared libraries -- single-threaded on an Apple M5 Max, both versions built from source at -O3:

	2.5	2.6.5
compress, -9 -n1	5.10s	4.68s	−8.2%
decompress, -t -n1	1.72s	1.57s	−9.0%

Single-threaded, because that isolates the code from the scheduler; across all eighteen cores the same corpus compresses in 0.35s against 0.32s and decompresses in 0.169s against 0.160s. Compressed size is unchanged -- 33,543,372 bytes from either version -- and each version reads the other's output back to the original bytes.

Installation

With Homebrew:

brew trust --formula caius72/lbzip2/lbzip2
brew install caius72/lbzip2/lbzip2

Homebrew refuses to load formulae from third-party taps until they are trusted. Installing by the fully qualified name above trusts this one implicitly, so the first command is only strictly needed if you tap first and then install lbzip2 by its short name; running it up front does no harm either way.

Homebrew core dropped its own lbzip2 formula: disabled on 2025-07-07 as unmaintained, removed on 2026-07-08. This tap is a replacement for it. If a copy from before the removal is still installed, brew uninstall lbzip2 first, since the two cannot occupy the name at once.

From source, with CMake 3.15 or newer and a C99 compiler:

cmake -S . -B build -DCMAKE_BUILD_TYPE=Release
cmake --build build
ctest --test-dir build      # optional, 1111 tests
cmake --install build       # honours --prefix and DESTDIR

Installing places lbzip2 in bin and the three manual pages in share/man. The lbunzip2 and lbzcat modes are selected by the name lbzip2 is invoked under, so create them as symlinks to the installed binary:

ln -s lbzip2 <prefix>/bin/lbunzip2
ln -s lbzip2 <prefix>/bin/lbzcat

lbzip2 is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

lbzip2 is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

A copy of the GNU General Public License is contained in the COPYING file.

The following is a list of subdirectories with explanation of their purpose:

build-aux - different auxiliary build scripts
man       - manual pages
src       - C source code of higher-level part of lbzip2
tests     - regression tests