Secret code

"I see, I see. A flying saucer has arrived for you. Here you go. Thank you much."

- Tom Nook

Secret codes, also known as passwords or simply codes, are passwords used in, and  to give and receive in-game items. The way codes work in each game varies.

Formatting and input
In, codes consist of 22 characters in two rows of 11. In, codes consist of 28 characters displayed as two rows of 14 characters each. In, codes consist of 32 hiragana characters again displayed as two rows of 16. Valid code characters include all uppercase and lowercase letters of the English alphabet, the numbers 0, 2, 3, 4, 5, 6, 7, 8, 9, the ampersand (&), the at sign (@), the pound (#), and the percent sign (%). The number  and capital   are interchangeable, as are the number   and capital  ; however,   is never generated in a secret code. When generated by Tom Nook, a capital  can be distinguished from a lowercase   by the serif drawn at both the top and bottom of its stem.

Passwords can either be input by sending them in a letter to a villager (in, and ) or telling them to Tom Nook (in  and  only). A password letter must be formatted in three lines: in Japanese games, the first line is the word あいことば (meaning secret password) and the second and third lines are 11 characters each; in, the first line must be the special key symbol, and the second and third lines are 14 characters each. The player will receive their item in a letter from a different character depending on the type of password two days later. While these are unlimited, Tom Nook will only distribute three items via password per game load. To redeem more items, the player must save and quit and then reload the game.

Types of codes
There are several types of secret codes the games can read. , and  each makes use of a variety of code types, each of which serves a different purpose and has a different origin. All code types follow the same description as outlined in the introduction and thus appear very similar to the untrained eye. They are listed below using the games' internal names and colloquial names.

Famicom codes
Famicom/"NES codes": These codes were used to distribute NES games on Nintendo's website. They are generated using input of the player's name and town name, and are sent by mail to random villagers. Official Famicom codes vary per game:


 * For, Famicom codes that were available to generate on Nintendo's website could be created for , , , (distributed in limited-time intervals throughout 2002) and  (discontinued sometime between 2015 and 2020). Famicom codes in  technically allow for any Famicom game, including the "Forbidden Four" (, ,  and )– the only way to obtain The Legend of Zelda without external modification in any game.


 * For, NES games for which codes could be generated on the website included , , , , and . were exclusively released on the official Animal Crossing website using NES codes and can only be obtained through this manner; universal codes cannot be generated for these titles. As the game's official site is no longer online, these five games are now solely available via third-party code generators capable of creating this specialized code type. Additionally, the "Forbidden Four" are no longer valid items for which a code can be created.


 * In, the only NES games not normally obtainable in-game (excluding the "Forbidden Four", which were removed) are and . The former had codes distributed for members of Panasonic hi-ho's "Doubutsu no Mori Photo Club" (どうぶつの森 写真くらぶ), while the latter does not seem to have been distributed.

NPC codes
NPC/Popular/"Character codes": These codes were generated upon voting for a character in Nintendo's Doubutsu no Mori+ Character Popularity Poll. Upon voting, the player would be able to generate a code based on their player and town names, which when mailed would receive a letter and gift from the character voted for (the letter also varies depending on whether it was sent to the character voted for). Translated versions of these letters appear in (even for new characters Franklin and Farley), although no similar poll seems to have been held for the game. However, these letters can be seen in-game if a third-party code is generated for them.

Card E codes
Card E/"e-Reader card codes": These codes are by far the most common type of code, due to working for any town and player. They are primarily seen written on the back of most and  e-Reader cards; they can also be seen by getting a certain score in minigames on the e-Reader. In, each character card will also show one of two codes when scanned on the GBA; these were replaced with messages from the character on the cards. Additionally, Nintendo's online code for the in  is this type of code. The way these codes work differs in each version:


 * In, Card E codes have a chance of no present at all (though a letter response is guaranteed), except if they are for a special character, in which case it is guaranteed. Most codes on the back of e-Reader cards only will give a random Famicom game with a 12.5% (1/8) chance, while the two GBA codes are always a particular item, usually from the villager's house, with one code having a 50% chance and one having a 25% chance. They must be sent by mail.


 * In, Card E codes are guaranteed a present, a particular item different from the one received when scanning the card at the eTM. If the letter is sent to the character on the card, there is either a 20%, 40%, 60%, or 80% chance of a common NES game and an inverted chance of the particular item. If the letter is sent to any other villager, the particular item is guaranteed. They can be sent by mail or redeemed with Tom Nook.


 * In, due to prioritization and accessibility of scanning e-Reader cards for gifts, using a code from in a letter will only give one of three items obtainable only in this way: the , the , or.

Magazine codes
Magazine/"contest" codes: These codes were usually included in magazines such as Nintendo Power and sometimes the Nintendo website, and as such work for any town and player. They are redeemed by mailing or, in only, telling them to Tom Nook. These codes include a "hit rate" value that could be 0%, 30%, 60%, 80%, or 100%. However, if the player loses they can simply try again. In practice, all official codes shared in magazines and websites had a 100% guaranteed hit rate. Due to this and their availability to any player, these and externally-generated Card E and Card E Mini codes (see below) are sometimes called "universal codes".

User codes
User/"Player-to-player" codes: Introduced in, these codes can be generated specifically for another player by telling Tom Nook their player and town name, and are redeemed with him as well. They intend to mimic the experience of a personalized delivery service. Nook will only generate passwords for items that are orderable from the catalog (plus Mushrooms and Candy).

Prior to the discovery of "universal" codes which work for any player regardless of name/town combination, fans created a group named Project Hyrule, whose sole goal was to amass a list of player-to-player codes for every item in the game. To take advantage of such a list, each member used the credentials Link in Hyrule when creating their town. After the advent and proliferation of code generators the group eventually became redundant, however their dedicated cryptologists did manage to generate many universal codes, which when redeemed at Nook's provide the player with a gift from "Project Hyrule."

Card E Mini codes
Card E Mini: Another code type introduced in, these cards were intended to be generated by winning e-Reader minigames. They are given to Tom Nook. They are another type of "universal" code that will work for any player, and are frequently used by unofficial password generators due to having the least restrictions on what items can be generated. If their hit rate index value is not set to 'one', the code will error with an 'incorrect password' error (see Code messages).

New NPC codes
New NPC: These codes were created using Flash plugins on the website which were available until 2020. They required sending an item with a user code to one of the new villagers using their names and Nintendo (にんてんどう) village; upon inputting this code with the player's name and town name into the plugin, a code would be generated for them from the villager. Villagers who could have codes created included: Moe, Gen, Curt, Carrot, Bella and Blaire in Series 1; Hopkins, Kid Cat, Frett, Sylvana, Peggy and Bree in Series 2; and Broccolo, Poko, Roscoe, Lolly, Megumi and Vivian in Series 3.

Object codes
Monument: Codes for generated based on player and town names on Nintendo's now-defunct Object Delivery Service website, which, when given to Nook, allow for certain Objects in the player's town. The price for the object is embedded in the password as a 6-character string. This limits the price of objects to between 0 and 999,999 Bells. The password also contains the acre which the object is attempting to be placed in. If the specified acre has no signboards, Tom Nook will tell the player it is impossible to build the object there, and to generate a new password.

Mario Theme codes
Some contest codes were used by Nintendo to distribute the Mario Theme, with codes for individual pieces listed in various issues of Nintendo Power magazine and on the official website. The Nintendo Bench code was distributed through Tips & Tricks magazine.

Cross-compatibility
The secret codes used in Animal Crossing are not compatible with any Japanese titles, nor can English code generators create codes that will work for Japanese games. Japanese universal codes do exist, however, and Japanese code generators have also been developed independently of their English counterparts.

Code messages
Different code types will result in different messages from Nook. These messages can be used to determine a code's type as well as to diagnose potential issues when a code is not working.

Wrong password: This message is received after entering an incorrect password.
 * "Now that's odd... I think there's something the matter with your password. Do you want to tell it to me again?"

Someone else's password: This message is received after entering a player-to-player, NPC, or NES code which was not sent to the player's specific character and/or town name.
 * "Oh?! What's this? You can't use that password, [player name]! Don't try to trick me by using someone else's password! Do you have a password of your own that you'd like to try?"

Send to animal: This message is received after telling Nook a villager code. This code type can only be redeemed by sending a letter to a villager in town. When mailing a villager code, make sure the key symbol appears by itself on the first line, the first line of code is placed on the second line, and second line of code sits on the third line of the letter. The villager will respond in a few days. If there is not a present attached to the letter then the code was typed incorrectly or is invalid.
 * "Eh? I'm sorry, but that password isn't valid here. Try sending it to one of the animals living in [player's town]."

NES game: This message is received when entering a Famicom/NES code. These codes had a few ways to be generated officially depending on the game and region.
 * "Ah, yes. You entered your name in a contest to win an NES game, eh? I see, I see. Well, here is your [item]. Thank you much."

Character popularity contest: This message is received after entering a character popularity contest code. These codes were only used in.
 * "I see, I see. You're looking for your prize for participating in the contest, aren't you? Don't worry! I won't make you tell me who you voted for! Thanks for participating. Here is your [item]. Thank you much!"

Contest winner: This message is received after 'winning' a contest code. Note that if the player attempts to reenter the code they may eventually 'win' the item.
 * "I see, I see. [A/An/This/Some] [item] has arrived for you from [contest name]. Please take your present. Thank you much."

Contest loser: This message is received after entering a losing contest code. Note that if the player attempts to reenter the code they may eventually 'win' the item.
 * "I see, I see... ...Now, this IS regrettable! Based on the notification I've received directly from [name]... it seems you are NOT a winner. But thank you much for trying!"

e-Card minigame winner: This message was intended to be used by e-Card minigames when a player won. It seems to have gone unused.
 * "I see, I see. This [item] is the prize for winning [minigame name]. Congratulations! Thank you much."