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


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 and other distribution and storage costs.

Programs and libraries compressed by UPX are completely self-contained and run exactly as before, with no runtime or memory penalty for most of the supported formats.

UPX supports a number of different executable formats, including Windows programs and DLLs, macOS apps and Linux executables.

UPX is free software distributed under the term of the GNU General Public License. Full source code is available.

UPX may be distributed and used freely, even with commercial applications.


UPX strengths in a nutshell:

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


UPX is Copyright © 2024 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.