Skip to content

How to use Ys VIII IT3 mods on the Switch

Jump to bottom
eArmada8 edited this page May 8, 2026 · 2 revisions

How to use Ys VIII IT3 mods on the Switch

The information in this guide is provided courtesy of Cutepatatas. Thank you very much for doing the research and sharing the information!

You will need a modded switch and the Ys VIII game. This guide assumes you are using Atmosphere as your custom firmware.

NOTE: This toolset (Ys8_IT3) is written to work with PC IT3 model assets. I do not believe that Switch IT3 model assets can be modified with the Ys VIII IT3 toolset, but many PC IT3 models can be used unmodified on the Switch.

Obtaining and unpacking data.dat

  1. First, Use DBI or nxdumptool to dump the game data. Locate data.dat in the game dump and copy it to an empty project folder.

  2. Rename data.dat to data.dat.original. We will not be modifying this file directly - we will instead be creating a new data.dat to used with LayeredFS.

  3. Download QuickBMS by Luigi Auriemma, as well as the Fafullfs BMS script for Nippon Ichi Software. Extract QuickBMS into the project folder, along with fafullfs.bms.

OPTIONAL: The following steps explains how to extract all the files from data.dat but you do not need to extract these files when inserting mods made for PC. Instead, create an empty folder called data, and create the folders inside that folder for the mods. For example, to mod /chr/pc/c005_p.it3, create the folders /chr/pc inside data and place your modded c005_p.it3 inside data/chr/pc.

  1. Extract data.dat.original into a folder called data by using QuickBMS (4GB+ version) from the command line with the following command:

quickbms_4gb_files.exe fafullfs.bms data.dat.original data

  1. Inside the newly created data folder, you will see all the extracted files. Character models are inside folders in the data/chr folder - for example player characters are in data/chr/pc and NPCs are in /data/chr/npc.

Inserting mods and repacking data.dat

  1. QuickBMS is also a bit quirky in the way it inserts files. It will not rebuild data.dat from scratch - instead it will only replace the files you want it to replace and leave the other files alone. So you actually want your /data folder to be mostly empty; remove all the files you don't want replaced from data. If you did not extract the files, that is fine.

  2. Replace the .it3 files you want to replace. Delete any unmodified files. Be sure you are replacing existing files, not adding new ones. It is important that you get the file paths correct. If you are unsure of your file paths, then extract the original data.dat as per the above instructions to inspect the correct file paths!

Hint: Uploading data.dat to the Switch takes a very long time (90 minutes or more), so be sure to use it3 mods that are known to work to first verify data.dat is being rebuilt correctly before inserting new experimental mods!

  1. First time only Make a copy of data.dat.original as data.dat:

copy /Y data.dat.original data.dat

This can take a while if you do not have an SSD - be sure to wait until you see 1 file(s) copied. and you are returned to the command point.

  1. Insert the files from data/ into your data.dat with the following command:

quickbms_4gb_files.exe -w -r -r fafullfs.bms data.dat data

NOTE: The data/ folder should contain only the modded files, not the originals. When using the -w -r -r mode (REIMPORT2) QuickBMS will append the modded files to the end of data.dat and point the entry in the table of contents to the end. This means that data.dat will grow a little in size each time you run this command.

  1. Transfer data.dat to your Switch. It belongs in sd:/atmosphere/contents/01007F200B0C0000/romfs/data.dat Drag-and-drop copy will fail if your SD card is in FAT32 format however, so use FTP to DBI. DBI has an FTP server, connect to it with FTP software such as FileZilla and transfer the file this way; DBI will automatically split the file into chunks in a way that is invisible to the Switch hardware.

  2. Close and reopen the game to test your new data.dat. If the game crashes immediately on loading, then data.dat is corrupt. If it crashes when loading the modded character, then the modded .it3 file is the issue.

Clone this wiki locally