KDiff3 is a file and folder diff and merge tool which

  * compares and merges two or three text input files or folders,
  * 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 network transparency via KIO,
  * option for 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.

KDiff3 is a KDE Application
KDiff3 requires KDE Frameworks packages provided by Slackware

NOTE: The historical Qt4-only build has not been ported to Qt5.