From KDE UserBase Wiki
      A tool to check, edit and merge differences between 2 or 3 files


    • compares and merges two or three text input files or directories,
    • shows the differences line by line and character by character(!),
    • provides an automatic merge-facility,
    • has an editor for comfortable solving of merge-conflicts,
    • provides networktransparency via KIO,
    • has options to highlight or hide changes in white-space or comments,
    • supports Unicode, UTF-8 and other file encodings,
    • prints differences,
    • supports version control keyword and history merging.

    The KDiff3 Handbook gives a detailed description of activities, in html form.