XZ Utils is free general-purpose data compression software with high compression ratio. XZ Utils were written for POSIX-like systems (GNU/Linux, *BSDs, etc.), but also work on some not-so-POSIX systems like Windows. XZ Utils are the successor to LZMA Utils.
The core of the XZ Utils compression code is based on LZMA SDK, but it has been modified quite a lot to be suitable for XZ Utils. The primary compression algorithm is currently LZMA2, which is used inside the .xz container format. With typical files, XZ Utils create 30 % smaller output than gzip and 15 % smaller output than bzip2.
XZ Utils consist of several components:
* liblzma is a compression library with API similar to that of zlib.
* xz is a command line tool with syntax similar to that of gzip.
* xzdec is a decompression-only tool smaller than the full-featured xz tool.
* A set of shell scripts (xzgrep, xzdiff, etc.) have been adapted from gzip to ease viewing, grepping, and comparing compressed files.
* Emulation of command line tools of LZMA Utils eases transition from LZMA Utils to XZ Utils.
While liblzma has a zlib-like API, liblzma doesn't include any file I/O functions. A separate I/O library is planned, which would abstract handling of .gz, .bz2, and .xz files with an easy to use API.
The most interesting parts of XZ Utils (e.g. liblzma) are in the public domain. You can whatever you want with the public domain parts.
Some parts of XZ Utils (e.g. build system and some utilities) are under different free software licenses such as GNU LGPL version 2.1, GNU GPL version 2, or GNU GPL version 3.