The Nintendo Wi-Fi Connection (commonly referred to as the Nintendo WFC, Wi-Fi, or simply WFC) is Nintendo's online service for the Wii and Nintendo DS. The service is so named because it originated on the DS, and the only way for the DS to connect to the internet was via Wi-Fi The Nintendo WFC allows players of games supported by the service to compete against each other online or access other features such as leaderboards or downloadable content. Mario Kart DS, along with Tony Hawk's American Sk8land, were the first games to support the Nintendo WFC. Mario Kart Wii also supports online play via the service. However, Nintendo announced in February 2014 that the Nintendo WFC servers would be shutting down on May 20, 2014. As such, it is no longer possible to play Mario Kart DS or Mario Kart Wii online without hacking the systems, meaning on such games, when connecting to Wi-Fi, the game tells you it no longer works..
Mario Kart DS
Since Mario Kart DS was the first game to use Nintendo WFC, the online mode is somewhat primitive. There is only one mode (battles are not supported), only 4 players can race at a time, there is no communication between players, and some tracks cannot be played online without the use of hacking tools. The player can choose to find a match with only opponents in their region or with anyone from around the globe. There is also a "Rivals" mode which attempts to match players up based on their skill levels (determined via GP rank and win/loss ratio). Prior to the race, all racers will choose a track; the track that will be played is chosen randomly from the votes, unless the same track is picked by more than one player. Players who have mutually registered each other as friends can also play with together online.
Players can draw their own custom emblems, which are displayed to opponents both during the race and on the matchmaking screen. Matches consist of four races, and performance is tracked by way of wins and losses. A win is recorded at the end of the match for every opponent that finished behind the player, and a loss is recorded for every opponent that finished in front of the player. For example, if the player finished second out of four racers, they would receive two wins and one loss. Racers who disconnect in the middle of a match are penalized by receiving one to three losses, one for each opponent in the match. This is done to discourage losers from powering off their consoles right before losing, to avoid giving a win to the winner.
Mario Kart Wii
As the Nintendo WFC had been out for quite some time by the release of Mario Kart Wii, Nintendo had plenty of time to make improvements to the service. The online multiplayer in Mario Kart Wii is much expanded and features a variety of improvements and features.
The maximum number of players in a race has been increased to 12, the same number as offline mode. All tracks are available online, and matches consisted of only one race instead of four to reduce the time commitment needed to start playing online. 12-player team battle mode is also available online. Two people on the same Wii console can play splitscreen online; the second person will be displayed as a Guest. Although there is no "Rivals" mode, Region, Worldwide, and Friend matchmaking modes still exist. The matchmaking system will try to group together players of near skill based on their VR (Versus Rating) rank, though it does not always work flawlessly, which can lead to a matches with one very skilled player in the same race as eleven new or unskilled players. Players select the track they wish to play on before the race, and the game will select randomly from all votes. Even if multiple players select the same track, it is possible for tracks selected by only one player to be picked.
Hacking is also something of a problem in Mario Kart Wii, since there is no anti-cheating system built into the game and Nintendo has no way of regulating online matches or banning hackers. There is still no way of communicating with other players, except during matches between registered friends.
Since emblems are no longer available, players are now represented by their Miis, which are displayed next to the names of racers and also in greater detail while matchmaking. Performance is tracked this time via the VR (versus rank) system. Each player has a VR rank score from 1-9999 that indicates how well they perform. The amount of VR gained or lost at the end of a race depends on the position a player finishes in and the VR rank of players who finished above or below them. For example, a player with 5000 VR who finishes in front of a 7000 VR ranked player will gain much more VR than if they had only beat a 4000 VR ranked player. Losing works in the same way; if a player with 9000 VR somehow finishes in last place behind many lower ranked players, they will lose a very large chunk of VR. Racers who disconnect will lose VR the same as if they had finished last place. Each racer also has their own rating for Battle Mode, which is called BR (Battle Rating) instead.
Leaderboards and Tournaments
In addition to racing, Mario Kart Wii also takes advantage of the Nintendo WFC to allow players to post their best time trial records and ghosts to the online leaderboards. Players can compare their own times to the best in their region or the world, with a distribution graph showing how their times compare to other players. The ghost of the world champion can be downloaded and raced, or the player can choose to download a "rival" ghost who is slightly faster than them. Mario Kart Wii also includes a separate channel, the Mario Kart Channel, which the user can install to their Wii's Home Menu, allowing them to view times and leaderboards without having to start the actual game.
Tournaments are challenges arranged by Nintendo that involve completing an objective in the least amount of time. This includes the usual complete three laps (usually on modified versions of usual tracks, and even sometimes on battle stages), as well as different events such as collect all of the coins as fast as possible. Nintendo changes the tournament once a month.
Friend codes are 12-digit long numbers that are Nintendo's system of allowing friends to play together, while avoiding the chaotic (and often not family friendly) "open" multiplayer of other systems such as Xbox Live or Playstation Network. In most Nintendo WFC games, there is no way to communicate with a player you meet through random matchmaking whatsoever; this is to avoid potentially offensive comments and situations. In addition, there is no guaranteed way to play with another player that you meet in random matchmaking. After you leave the match, you will probably never encounter them again.
Players who are registered as friends can play with each other by selecting the Friends option from the Nintendo WFC menu and can have limited communication. For two players to be recognized as friends and therefore be able to play with each other, both must add each other's 12-digit friend code into their friends lists. At the Mario Kart Wii main menu, your friend code is displayed under your name on your License. Note that each license has a different friend code.
Nintendo's online and friend code system has been frequently criticized as being too restricted and cumbersome, with critics saying it tries to hard to avoid potentially unfriendly situations at the very large expense of reduced interaction between players.