Smash World (スマプラス, Smash Plus) is a supplementary service and social app for Super Smash Bros. Ultimate. It became active on April 17th, 2019, as a free service and accessible through the Nintendo Switch Online app on smartphones and tablets.
The service allows players to view, post, and download videos made with the Video Editor or stages made with the Stage Builder in Ultimate within the service for use in the game itself. It also allows players to voice chat with others in battle arenas, check in-game notifications and create nameable spirit teams from those already in the player's possession.