In which Just Dance game was the 'World Dance Floor' online mode introduced?

The Just Dance game that introduced the World Dance Floor online mode was Just Dance 2014.

The mode enabled players to compete online against other players simultaneously on the same song. Participants could join large multiplayer sessions, compare their performance, and see results after each track.

Just Dance 2014 described World Dance Floor as a major new feature and a significant departure from earlier entries. It also expanded the series’ online functionality beyond basic single-player and local multiplayer experiences.

Just Dance 4 and Just Dance 3 preceded the mode’s introduction. Later games, including Just Dance 2015, retained or expanded the feature rather than originating it. The correct canonical answer is therefore Just Dance 2014.