UPX is a free, portable, extendable, high-performance executable packer for several executable formats.

Please also see the Wikipedia entry for some more background info.

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UPX achieves an excellent compression ratio and offers very fast decompression. Your executables suffer no memory overhead or other drawbacks for most of the formats supported, because of in-place decompression. UPX strengths in a nutshell:

You probably understand now why we call UPX the "Ultimate Packer for eXecutables".


UPX is Copyright © 1996-2016 by Markus F.X.J. Oberhumer, László Molnár & John F. Reiser.

The term UPX is a shorthand for the Ultimate Packer for eXecutables. All trademarks, brands, and names are the property of their respective owners.