WCopyfind is an open source windows-based program that compares documents and reports similarities in their words and phrases. It is free and available to anyone. It is licensed under the Gnu Public License, which basically means that you can do whatever you like with it except to try to sell it to someone else.
Unlike most modern software packages, WCopyfind is a single executable file. You don’t install it, you just run it. Simply click on the link to download the executable file. If you’re running a 64-bit version of Windows, you can select the 64-bit executable, which runs about 10-20% faster than the 32-bit version. Place that file in a convenient location and double-click on it to execute it. It stores its setting settings in the windows registry, but otherwise it doesn’t have any lasting effect on your computer.
WCopyfind is pretty simple to use, but some of the settings need explanations.
As open source software, you’re welcome to tinker with WCopyfind to add features or make it behave differently.
I have been asked many times to explain how these comparison programs work and how they manage to complete their work so quickly. At long last, I have written an explanation of those programs. For more information, you’ll simply have to read the source code, which is now much clearer than it used to be.