The Apache Commons Compress library defines an API for working with ar, cpio, Unix dump, tar, zip, gzip, XZ, Pack200 and bzip2 files.

The compress component is split into compressors and archivers. While compressors (un)compress streams that usually store a single entry, archivers deal with archives that contain structured content represented by ArchiveEntry instances which in turn usually correspond to single files or directories.

Currently the bzip2, Pack200, XZ and gzip formats are supported as compressors where gzip support is mostly provided by the java.util.zip package and Pack200 support by the java.util.jar package of the Java class library. XZ support is provided by the public domain XZ for Java library.

The ar, cpio, dump, tar and zip formats are supported as archivers where the zip implementation provides capabilities that go beyond the features found in java.util.zip. As of Commons Compress 1.3 support for the dump format is read-only.

The compress component provides abstract base classes for compressors and archivers together with factories that can be used to choose implementations by algorithm name. In the case of input streams the factories can also be used to guess the format and provide the matching implementation.