Dzip is a compressed archive utility, and its native .dz file format. It was developed by Stefan Schwoon and Nolan Pflug. It uses zlib compression.
It was originally promoted as being useful for compressing demo files for the video game Quake, but it can be used for general purposes.
There is a GUI version for Windows, and a command-line version that is cross-platform and open source.
Files start with ASCII "