xxdiff is a graphical file and directories comparator and merge tool.

Features

 * Comparing two files, three files, or two directories (shallow and
   recursive);
 * Horizontal diffs highlighting; Files can be merged interactively and
 * resulting output visualized and saved;
 * Has features to assist in performing merge reviews/policing; Can
 * unmerge CVS conflicts in automatically merged file and display
   them as two files, to help resolve conflicts;
 * Uses external diff program to compute differences: works with GNU
   diff, SGI diff and ClearCase's cleardiff, and any other diff whose
   output is similar to those;
 * Fully customizable with a resource file; Look-and-feel similar to
 * Rudy Wortel's/SGI xdiff, it is desktop agnostic (i.e. will work
   equally well with KDE or Gnome);
 * Features and output that ease integration with scripts.

xxdiff does not support comparing files encoded with Unicode. Also, it
does not support inline editing of the diffed files. If you need these
features, you could try emacs or Meld (although both of these lack some
of the most interesting features of xxdiff).