1. an efficient live-compressor for executables UPX is an advanced executable file compressor. UPX will typically reduce the file size of programs and DLLs by around 50%-70%, thus reducing disk space, network load times, download times etc. The current version can compress executables for DOS, Linux/ELF (i386 only!) and some other files for different OS. NOTE: This package is based on the UCL library, which is licensed under GPL. From Debian 3.0r0 APT