A friend code is a code that is unique to every player and is generated when the player plays Super Smash Bros. Brawl for the first time over Nintendo Wi-Fi Connection. Another friend code is generated when the player first opens the Friend List application while connected to the Internet on the Nintendo 3DS. The same also applies to the Nintendo Switch. In Brawl, Super Smash Bros. for Nintendo 3DS, and Super Smash Bros. Ultimate. player must register each other's friend codes in order to play With Friends, or to join a friend's Battle Arena in Ultimate.
Friend codes are not used by the Wii U; instead, players are identified by their Nintendo Network username, and can send friend requests to other players via the Friend List or Miiverse. Super Smash Bros. for Wii U also allows players to send friend requests after playing an online match.
Friends must give these codes to each other before they can play together online. The format is three sets of four-digit numbers, such as 0000-0000-0000. In Brawl, players can check their own friend code and add others on the friend roster; a maximum of 64 friends can be registered. Super Smash Bros. for Nintendo 3DS and Ultimate do not include such functionality in-game, as the 3DS uses a single friend code for the system instead of having separate codes for each game like the Wii and DS. Players cannot view each other's online status until they have both registered each other's codes.
After registering a code, the player can play with the other player in a few different modes, including a regular Versus match (with custom taunts usable), a Multi-Man mode match with the other player as a teammate, or Home-Run Contest.
Friend codes are normally no longer usable in Brawl due to the shutdown of the Nintendo Wi-Fi Connection in 2014. However, it is still possible for Brawl to be played online via hacks and private servers, or via the emulator Dolphin.