UPX.EXE is a portable extensible and high-performance compression program for several different executable formats. It achieves an excellent compression ratio and offers * very * fast decompression. Your executables do not suffer from any memory overhead or other disadvantages for most supported formats due to local decompression.

Although you are free to use UPX for both non-commercial and commercial executables we would appreciate it if you could list UPX and yourself in the documentation including a link to the UPX home page.

(Excerpt from the manual).

 

More detailed information is available at https://upx.github.io/