 A main feature of the Unarchiver is its ability to handle many old, obscure formats like StuffIt as well as AmigaOS disk images in LZH, LZX, 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.