UPX is described as '(Ultimate Packer for eXecutables) 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' and is an app in the File Management category. There are more than 10 alternatives to UPX for a variety of platforms, including Windows, Linux, Online / Web-based, Android and iPhone. The best alternative is FileOptimizer, which is both free and Open Source. Other great apps like UPX are ExEinfo PE (Free), Appetize.io (Freemium), VMProtect (Paid) and FUPX (Free).
VMProtect Ultimate - All-In-One Solution For Software Licensing And Protection. VMProtect protects code by executing it on a virtual machine with non-standard architecture that makes it extremely difficult to analyze and crack the software.
ASPack makes Windows programs and libraries smaller up to 70% (the compression ratio is higher than the ZIP standard by 10-20%), and decrease load times across networks, and download times from the internet.