Xz

xz is a lossless data compression program and file format which incorporates the LZMA/LZMA2 compression algorithms.

These are the same compression formats used by the 7-Zip program and its command-line version p7zip. However, .xz has a different file format, which is not compatible with the .7z format used by 7-Zip; notably, .7z lacks support for Unix-like file system metadata.

xz compresses/decompresses single files as input, and does not bundle multiple files into a single archive. It is therefore common to compress a file that is itself an archive, such as those created by the tar or cpio Unix programs.

Although the original 7-Zip program, which implements LZMA2 compression, is able to produce small files at the cost of speed, it also created its own unique archive format which was made primarily for Windows and did not support Unix functionality.

An implementation of the xz file format is freely available online as XZ Utils. It is licensed under the terms of the GNU LGPL and GNU GPL, with the bulk of the software (e.g., liblzma) in the public domain. Starting from 5.2.0, the command-line program xz supports multi-threaded operations which were only available in a fork called pxz previously. Version 1.22 of GNU tar supports using this software to handle xz files transparently. FreeBSD tar has supported xz transparently since r191190 (released on April 17, 2009).

7-Zip has supported xz since 2009's version 9.04 beta (stable since 2010's 9.20) and WinRAR since version 5.