HKI is the "native" format of WinHKI, another of the many archiving programs which supports a number of popular archive formats as well as introducing a new one of its own. It is named after the initials of its author (Hanspeter Karl Imp).
The WinHKI program (for Windows, as its name implies) comes in both free and paid versions. The paid version will create HKI archives using any of three compression techniques optimized for different sorts of files, while the free one will only compress with one of these techniques (though it will decompress archives compressed with any of them).
The compression methods are:
- HKI1: best for MP3, CD images. Supported by free version.
- HKI2: best for programs and documents.
- HKI3: best for some other sorts of data; very fast.