The .xz file format

The .xz file format is a container format for compressed streams. There are no archiving capabilities, that is, the .xz format can hold only a single file just like the .gz and .bz2 file formats used by gzip and bzip2, respectively.

Compared to a few other popular stream compression formats, the .xz format provides a couple of advanced features. At the same time, it has been kept simple enough to be usable in many embedded systems. Here is a summary of the features:

Once a new filter or integrity check has been added to the .xz file format specification, it won't be removed. This is to ensure that all .xz files, that use only the filters defined in the .xz file format specification, can always be decompressed in future.

New filters, integrity checks, or other additions to the .xz file format are unlikely to occur very often. Useless bloat can be avoided when new filters are added to the official list only when the new filters are clearly useful.

The official .xz file format specification

The latest version of the official .xz file format specification is available in plain text form at

Specific versions of the specification:


At least the following software support the .xz file format: