Back to Super Dodo Terminal for the full SDT overview.
New here? Work through Getting Started first — especially recommended file organization (separate folders per console). That habit makes this tool much safer and easier.
) to access this tool.
What It Does
Island Migrator merges a treasure island onto a base save that already works on your Switch.
After Nintendo’s recent updates, saves from another console (or injected layouts) can cause online errors such as 2219-4201 and 2219-4301 when opening gates, flying, or going online. This tool addresses that: it copies layout, villagers, items, terrain, buildings, designs, and related data from your treasure save, while keeping the console ownership behavior of your base save so online play stays stable.
Base save
The Switch is “allowed” to use this save online.
Treasure save
The island you want to look and play like.
Output
A new JKSV-style folder you copy to your SD card and inject.
💡 Tip — The window has two tabs: Migrate (day-to-day use) and Technical Details (same deep dive as in the app). On Migrate, the yellow summary box lists everything that will be included and updates when you change checkboxes.
Recommended file organization
The Island Migrator requires clean, consistent file organization.
If you mix up saves between consoles, you will continue getting online errors.
1.
Name each console
Use something simple like 1, 2, 3. Masking tape on the back works perfectly.
Use something simple like 1, 2, 3. Masking tape on the back works perfectly.
2.
Create a folder for each console
Example: Console 1, Console 2, Console 3
Optional: use these icons to visually separate them.
Example: Console 1, Console 2, Console 3
Optional: use these icons to visually separate them.
3. Store saves inside each console folder
Use clear names like:
Use clear names like:
5 - Base SaveGarden5Clothes5Materials5
Always keep a working base save for every console
A base save is any save that can successfully open the airport gates without an error code.
A base save is any save that can successfully open the airport gates without an error code.
- Even a ready-to-use Treasure Island can be used as a base
- Make a copy and rename it to "# - Base"
- This gives you a safe starting point for migrations
With this setup, you're always 2–3 steps away from fixing most online errors.
Safety First
Keep backups of all original save folders until you’ve loaded the new island in-game and confirmed gates and online behavior. Do not delete your originals until you’re sure the migrated save is good.
Each Switch needs its own base save — they are not interchangeable. Label consoles and folders so you never mix them up.
One-Time Setup: Base Save (Per Console)
Do this once per Switch you want to migrate onto. If you already have a save on that console that opens the airport and flies without errors, use a JKSV dump of that as your base and skip to Using the Tool.
1.
Every console needs its own base save — one that fully loads, can open the airport gates, and can fly out without error codes. If it works online on that console, it’s a valid base.
2.
If your current save only throws errors, dump it with JKSV and set it aside; you can migrate that layout onto a fresh base later with this tool.
3.
To create a fresh base: delete ACNH save data in System Settings, start a new island, use the Map Editor if you want to speed up day one (give yourself branches & fruit), sleep in the tent, save and exit, then time travel one day forward in System Settings.
💡 Tip — Instant Text in SDT can speed up NPC dialogue while you set this up.
4.
Confirm the airport works (open gates / fly). Then use JKSV to export a new dump. That folder is the base save for that console only. Repeat for each Switch. Store bases in clearly named folders.
Using the Tool
Work on the Migrate tab.
1.
Read the red backup banner and the short pink info note at the top of the window — they match the important warnings above.
2.
Open Setup Guide (read this first if it's your first time) in the app for the full in-window walkthrough.
3.
Under Save Folders:
Base (fresh working save): Browse and select the JKSV folder for the destination Switch (must contain
main.dat and Villager0\personal.dat).
Treasure island save: Browse and select the layout you want to copy (must contain
main.dat; Villager0\personal.dat should be present for full player data — if personal files are missing, the tool logs a warning and skips player import).
4.
Output folder name: type a name (usually the island name). This becomes the JKSV folder name on your SD card.
5.
Optional Unlocks: choose what to apply on top of the merge. When you pick the treasure folder, the app detects what’s already fully unlocked and shows a green style on those rows; you can still toggle boxes manually.
- Full Critterpedia
- All 40 pocket slots
- Sable friendship (max) — custom fabric at the sewing machine only works if Able Sisters is built on the island.
- All 200 custom design slots
- All DIY recipes
- Island Designer (all permits)
6.
Review the yellow What gets transferred summary in the app.
7.
Click Merge & Save. Choose the parent folder for the new folder (the app creates
...\YourOutputName\ inside it). If that folder already exists, you’ll be asked to overwrite.8.
When migration finishes, a message shows a short log and the output path.
After Merge
1.
Connect the destination Switch to your PC.
2.
Copy the output folder into the correct JKSV location on the SD card.
3.
Use JKSV to inject that save on the target console.
4.
Load ACNH and confirm airport / gates / flying and any optional unlocks you checked.
Sanity check — on first load, the game should not say the save isn’t connected to existing users. If you see that, the base save wasn’t set up, dumped, or selected correctly for that console.
What's Next
- Super Dodo Terminal — Main window, profiles, gates, map tools
- Profiles & Switch IPs — Label Switches to match your save folders
- Getting Started — JKSV, organization, first island
- SDT General Settings — App-wide options
Technical details (click to expand)
For forks, troubleshooting, or curiosity — this mirrors the Technical Details tab in SDT.
Dependencies
Merge logic uses NHSE (NHSE.Core, etc.) from the app folder. If migration fails with a missing-DLL style error, ensure NHSE.Core.dll (and related NHSE assemblies your build ships with) sit next to the running app, or run from the correct bin output after a successful build.
What stays from the base
The base directory is copied to the output first, then selected regions from the treasure main.dat / personal.dat overwrite the merged data. Murmur3 hashes are recomputed for touched regions and the save is re-encrypted (AES-CTR with a fresh seed) automatically.
Identity handling
After copying identity-related blocks from the treasure personal.dat, the tool search-and-replaces the base save’s town and player identity bytes throughout main.dat and personal.dat with the treasure island’s identity (same general approach as NHSE’s ChangeIdentity()).
Regions copied from treasure main.dat (always)
- Villagers (10 NPCs), custom designs (normal + PRO + flag + tailor), field items, terrain, buildings, acres, design map, villager houses, island event flags
Regions copied from treasure Villager0\personal.dat (when present)
- LookPack (appearance / outfit), GSavePlayerId, player event flags
Other files
landname.dat— copied in full from the treasure folder.
Optional unlocks (summary)
- Critterpedia — ItemCollectBit region in
personal.dat - 40 pockets — event flags + pocket/bag counts in
personal.dat - Sable — EventFlagPlayer entries
- 200 design slots — event flags + pattern edit bytes in
main.dat - All DIY recipes — recipe bit block in
personal.dat - Island Designer — EventFlagLand + EventFlagPlayer combinations
Exact offsets and IDs match Island Migrator → Technical Details in the app and Core/SaveMerger.cs in the Super Dodo Terminal source.
