StreetPass is a software program that comes, pre-installed, with a Nintendo 3DS or 3DSXL. When StreetPass is on your 3DS will search for other 3DSs, wirelessly, that have StreetPass turned on. The 3DS will search for other players when it is in sleep mode, and when playing some 3DS games (this depends on the game and if it is using a wireless connection). When the system finds another 3DS, it will swap information, like your Mii and recently played games. Once the information has been swapped, the 3DS will notify you with a green light above the button pad. Various games may use this information that has been swapped.
The function was born out of a similar idea found in some DS titles such as Dragon Quest IX known as Tag Mode. However, this Tag Mode was software specific and had no internal back end in the DS itself beyond its ability to allow wireless broadcasting and reception while in sleep mode. With StreetPass, the user can save data to the SD card, allowing the game's StreetPass functions to operate even when the game card isn't inserted.
Examples of Use
Dead or Alive: Dimensions
Players that exchange Dead or Alive: Dimensions StreetPass data will be given the opportunity to fight a CPU-controlled version of the opponent's most-used character. The skill of the opponent is based on the letter-grade skill ranking that the opponent has earned through battling other players.
Super Street FIghter IV: 3D Edition
In Super Street Fighter IV, players are able to collect figures of the various fighters, each with their own stats, and assemble a team of five fighters to serve as a StreetPass team. When another player with SSFIV StreetPass data is encountered, the player will then be able to pit their team against the opponent's in an automated battle that pairs each of the player's figures against the opponent's figures in a series of five one-on-one matches.
Samurai Warriors: Chronicles
As in Super Street Fighter IV, the player creates a team of five officers in Samurai Warriors: Chronicles to do battle with an opposing team. However, rather than be paired off in a series of one-on-one fights, the officers fight together as a group. Officers fall into different categories with skills ranging from being able to heal and support party members to attacking multiple enemies at once. Battle effectiveness depends on the officers used in the party, as well as which battle formation is selected.