[[caption-width-right:350:Meet Nikki: Your helpful resident Mii of SwapNote]]

Swapnote, or ''Itsuno ma ni Koukan Nikki'' in Japan (''Nintendo Letterbox'' in the EU, ''Nintendo Mailbox'' in some other areas) was a free messaging app on the Nintendo3DS released in late December of 2011. Unlike other messaging apps that let you give small blurbs of text, you essentially send scribbled notepad messages which are "redrawn" to the recipients, and even have the ability to draw [[ThreeDMovie in 3D]] along with attaching 3D pictures or sound bites. These messages can be sent to friends online via [=SpotPass=] or [[SocializationBonus person-to-person]] [=StreetPass=].

Aside from the ability to scribble notes, it is possible to make {{Yonkoma}}, {{RPG}}s, and if skillful enough, small animations. It is even possible to set up [[AlternateRealityGame Alternate Reality Games]] given the ability to pass messages from person-to-person. You can also unlock various Stationery and features to use that can be purchased with the Nintendo3DS's in-system currency Play Coins.

Perhaps most interesting of all is the popularity it has garnered not just from its messaging functions but from Swapnote's [[ExpositionFairy guide]] in the form of a Mii called Nikki (in the bottom left side of the pic to the right). Already various [[FanArt fanart]] of [[{{Meganekko}} her]] [[EnsembleDarkhorse have]] [[RuleThirtyFour popped-up]] since the app debuted. At New Year's Day at 2012, Nintendo themselves sent out a new stationery (that can be acquired by simply having a friend send a message with the new stationary to you), along with a QR Code of Nikki's own official Mii usable in Mii Maker.

To protect minors, Nintendo discontinued the application's [=SpotPass=] features on November 1, 2013, due to users sending each other offensive material.

Has nothing to do with ''Manga/DeathNote''.

!! ''Swapnote'' provides examples of:
* {{Adorkable}}: Nikki. C'mon, look at her.
* DoubleUnlock: Once you unlock the ability to attach recordings to your notes, you still need to pay 10 Play Coins to actually use it.
* ExpositionFairy: Nikki.
* MeaningfulName: ''Nikki'' is Japanese for journal/diary.   ''Koukan nikki'' is a form of exchange jounal among close friends.
* {{Meganekko}}: Nikki.
* RolePlayingGame: [[http://www.youtube.com/watch?&v=YrDFhhh-MuQ This video]] provides an example of how to create a simple [[TabletopGames tabletop RPG]] within Swapnote.
* SpiritualSuccessor: To the DS's Pictochat.
* [[StopHelpingMe Stop Helping]] [[JustForPun Mii]]: Nikki can sometimes be this. Luckily you can skip though her messages stating you have unlocked things like attachments and 3D drawing. Which leads to...
* UnlockableContent: The ability to send pictures and sound attachments along with 3D writting are unlocked as you save/send more messages. Additional Stationery can be purchased via Play Coins.
* {{Yonkoma}}: You are given up to four pages for each message you send.
* VariableMix: The background music changes when reading, writing, or browsing your notes.
* VideogameCrueltyPotential: You can send anything to anyone in your friends list. Even [[RuleThirtyFour that.]] (Which ultimately contributed to it going offline.)