The Unarchiver

The Unarchiver is a proprietary freeware data decompression utility, which supports more formats than Archive Utility (formerly known as BOMArchiveHelper), the built-in archive unpacker program in macOS. It can also handle filenames in various character encodings, created using operating system versions that use those character encodings. The latest version requires Mac OS X Lion or higher. The Unarchiver does not compress files.

Prior to the purchase by MacPaw in 2017, The Unarchiver was previously free software licensed under the LGPL, up to version 3.11.1 (released 2016). The Unarchiver version 3.11.1 provided a free-software implementation of extraction of RAR versions up to RAR5.

The corresponding command line utilities  and   are free software licensed under the LGPL  run on Microsoft Windows, Linux, and macOS.

A main feature of the Unarchiver is its ability to handle many old or obscure formats like StuffIt as well as AmigaOS disk images and LZH / LZX archives, and so on. This is credited in its source code to the use of libxad, an Amiga file format library. Ågren also worked to reverse engineer the StuffIt and StuffIt X formats, and his code was one of the most complete open source implementations of these proprietary formats.