Apps to 3-Way Merge

Git Extensions is a feature-rich, open-source graphical user interface (GUI) for Git on Windows. It provides developers with a more intuitive way to interact with the Git version control system, integrating deeply with the Windows environment for enhanced productivity.

TortoiseHg is a comprehensive graphical user interface (GUI) for the Mercurial distributed version control system. It provides a user-friendly way to manage your repositories, track changes, and collaborate with others, particularly well-integrated with the Windows File Explorer.

WinMerge is an open-source differencing and merging tool for Windows. It helps you compare, synchronize, and merge both files and folders, highlighting differences visually and providing robust tools for handling conflicts.