The Nintendo DS is region free
in the sense that any console will run a Nintendo DS game purchased anywhere in the world; however, the Chinese version games can only be played on the Chinese iQue DS, whose larger firmware chip contains the required Chinese character glyph images. Although the Nintendo DS of other regions cannot play the Chinese games, the iQue DS can play games of other regions. Also, as with Game Boy games, some games that require both players to have a Nintendo DS game card for multiplayer play will not necessarily work together if the games are from different regions (e.g. a Japanese Nintendo DS game may not work with a North American Nintendo DS game, even though some titles, such as Mario Kart DS and Pokémon Diamond and Pearl versions are mutually compatible). With the addition of the Nintendo Wi-Fi Connection, certain games can be played over the Internet with users of a different region game.
Some Wi-Fi enabled games (e.g. Mario Kart DS) allow the selection of opponents by region. The options are "Regional" ("Continent" in Europe) and "Worldwide", as well as two non-location specific settings. This allows the player to limit competitors to only those opponents based in the same geographical area. This is based on the region code of the game in use. The Nintendo DSi, however, has a region lock for the DSiWare downloadable games, as well as DSi-specific cartridges. It still runs normal DS games of any region, however.