Xdelta is a utility which is used to generate a file of differences between two binary files. This effectively means only modifications made between the two binary files are saved; the resulting file is easily shared to another user, who can use it to generate a modified file from the original file. This is especially useful if the original file contains copyrighted material (e.g. game executable, rom) or the original file's filesize is huge. While the examples in this article use regular Windows executables (.exe), Xdelta can be used with any kind of binary file.
xdelta -d -s old_file delta_file decoded_new_file
xdelta3.exe -e -s old_file new_file delta_file