Wikipedia
WinMerge
WinMerge is a free software tool for data comparison and merging of text-like files. It is useful for determining what has changed between versions, and then merging changes between versions.
The project is currently in background development of version 3.x, with no known date for release. No commits have been made to the 3.0 codebase since 2011.
In 2011 a fork of the 2.x codebase titled "WinMerge 2011" was created. This new branch has continued to see active feature and bug fix development. It has also removed ATL/ MFC dependencies so that WinMerge can be built using the free Visual C++ Express editions.
WinMerge runs on Microsoft Windows.