Dialog in this game is stored in Message Studio Binary Text (MSBT) files. There are separate archive files that the MSBT files will be in depending on its type of dialog, and it is named based on its region and language. All dialog files are stored in the Message directory in the games romFS.
|Dialog||Text for menus in the game|
|LayoutMsg||Text for menus in the game|
|System||Text for menus in the game|
|Mail that can be sent by villagers or special NPC's|
|String||Names of villagers, NPC's, items, along with catchphrases|
|TalkFtr||Text for interacting with furniture|
|TalkObj||For things like the Nook Stop, Lloid, Snowman, the drop-off box, etc.|
|TalkSNpc||Text for special NPC's like Isabelle, Wilbur, Tom Nook, etc.|
|TalkSys||For text when the PC is talking to themselves, like catching critters.
Or menus the PC opens themselves, like the save dialog.
|Tutorials||Any text during the games tutorial.|
For dialog types that correlate to villagers (TalkNNpc and Mail), there will be 8 folders. Each folder represents a different personality type.
- B1_Bo: Lazy
- B2_Ha: Jock
- B3_Ko: Cranky
- B4_Zk: Smug
- G1_Fu: Normal
- G2_Ge: Peppy
- G3_Ot: Snooty
- G4_An: Sisterly
Special NPC's aren't grouped in with normal villagers though. For Mail, inside SNpc, there will be 22 folders. Each folder of course representing a different special NPC. The HHA, Nintendo, Catalog Shop, Milage Program, Dodo Airlines, Faraway museum, Snowman, and the ATM have separate folders named after them respectively.
- alw: Reese
- bey: C.J.
- boc: Daisy Mae
- bpt: Katrina
- chy: Flick
- fox: Redd
- gul: Gulliver
- gulB: Gullivarrr
- hgc: Label
- man: Wardell
- mnc: Niko
- otg: Lottie
- owl: Blathers
- pkn: Jack
- pyn: Zipper
- rco: Tom Nook
- slo: Leif
- spn: Harvey
- sza: Isabelle
- tap: Luna
- tkk: K.K.
- xct: Rover
Below is a list of all special NPC's. Most don't send mail, but still have abbreviated names to refer to them. There's 64 SNpcs like this. Expand the table below to see.
For TalkNNpc, there is more folders that are named based on what they are. For example, the React folder has dialog on when the villager is doing/experiencing an action, like sitting down or crafting a DIY. Or the Dream folder which has dialog when speaking to a villager in a dream. The rest of them are self-explanatory.
As you can see above, the way that they're named is very straight-forward.
They start with a dialog type, then the region and language. So, if you were looking for the LayoutMsg in German, it would be named LayoutMsg_EUde.sarc.zs
In Switch Toolbox, open the folder to the ACNH romFS folder. All text is stored in sarc.zs files, in the Message folder. Expand the folder, double click on the file to open it, and then you'll see the contents of it. In the Toolbox, you can edit MSBT files, but it's better to use Kuriimu.
With the MSBT file you're looking to edit, right click it then select Export Raw Data. You can save it to wherever you'd like. Now in Kuriimu, drag the file onto the window to open it. For more on what you can do with MSBT files, read MSBT Functions. Anyway, Make your changes, and save. Back in the toolbox, take find the MSBT you just extracted and delete it. Now, right click the folder it was in, select add file, and select the edited text file. As an example, you open the TalkFtr_USen.sarc.zs, and make changes to the FTR_TrashBox.msbt. Delete the original MSBT, right click the sarc, and click Add File.
To get your edits to show, right click the sarc.zs that you opened, and press Save. Make sure to save the file with ZSTD, and it's named the same. On your SD card go to
/atmosphere/contents/, and make the directory
01006F8002326000/romFs/Message. Copy the file in there, load up your game, and you'll see your changes.
If the game crashes instead, place this file in
/System/Resource/ in the romFs folder. If you do not have this directory, create it. It should work now. Under normal circumstances, with ACNH, loading a file that's much bigger or smaller than the original, the game crashes. This file disables the games RAM management, so it will load any mod no matter the size.