KDiff3

KDiff3 is a diff and merge program that compares or merges two or three text input files or directories, shows the differences line by line and character by character (!), provides an automatic merge-facility and an integrated editor for comfortable solving of merge-conflicts, supports Unicode, UTF-8 and other codecs, autodetection via byte-order-mark "BOM", supports KIO on KDE (allows accessing ftp, sftp, fish, smb etc.), printing of differences, manual alignment of lines, automatic merging of version control history ($Log$), and has an intuitive graphical user interface.