UPX

PX, which is an acronym for Ultimate Packer for eXecutables, is a command line tool that allows you to reduce the size of different executable file formats. UPX not only achieves a compression ratio which is superior to that of the Zip format, but also allows for a better decompression speed (10 MB per second on an ancient Pentium 133). Another interesting thing about UPX is the fact that it is portable and multi-platform, which allows you to execute it on practically any device or operating system. It supports the following executable file formats: atari/tos, djgpp2/coff, dos/com, dos/exe, dos/sys, linux386, rtm32/pe, tmt/adam, watcom/le and win32/pe.