The current transposition feature on ultimate-guitar.com only produces sharp (#) chords, with no means to change them into flat (b) chords. It leads to chord names like ‘D#’ or ‘A#’ which are quite unusual and disturbing to many musicians, who would prefer ‘Eb’ and ‘Bb’ in these cases.
This extension addresses that need by providing a button that changes every sharp chord into the enharmonic flat chord.