Custom Switch Game Cart with microSD

[MateyMaterson]

Hello, I was wondering if someone created a custom switch cart that could take a microSD card similar to the R4 cards from the NDS days. I wanted a fast save file transfer method between my 3DS and switch.

 

[Nephiel]

Switch saves are always stored on the console memory, not on the carts. What exactly do you want to transfer between 3DS and Switch?

Closest thing to the R4 of old for Switch is the MIG, but that only works with complete game dumps, and there is a very high risk of ban unless the dumps are unique. IMO it's better to mod the Switch so it can run homebrew.

 

[MateyMaterson]

Switch saves are always stored on the console memory, not on the carts. What exactly do you want to transfer between 3DS and Switch?

Closest thing to the R4 of old for Switch is the MIG, but that only works with complete game dumps, and there is a very high risk of ban unless the dumps are unique. IMO it's better to mod the Switch so it can run homebrew.

Sorry, I should have specified that I have a modded switch and am speaking about a new way to transfer save data in and out of the switch. The save data that I want to move around currently is a .sav for GBA games. So pretty much I just need to be able to manipulate files in and out of an external SD card.

 

[Moseii]

cant u just use FTP? pretty sure it less tedious than doing it manually and it wont take long to transfer because its just save files, no?

 

[impeeza]

Hello, I was wondering if someone created a custom switch cart that could take a microSD card similar to the R4 cards from the NDS days. I wanted a fast save file transfer method between my 3DS and switch.
View attachment 554423

Will not be possible.

you can no run unsigned code from a switch cartdrige.

The saves are stored encrypted on the System NAND or User partition not at the cartdrige.


use JKSV which can backup any save to a cloud or webdav server.

 

[MateyMaterson]

cant u just use FTP? pretty sure it less tedious than doing it manually and it wont take long to transfer because its just save files, no?

Wouldnt this require wifi and a laptop? The end goal here is to transfer .sav files between a 3DS and a switch, so I am trying to find a solution that only needs those 2 devices. I happen to run into this problem frequently when I'm road tripping with my family. So I'd prefer a solution with no wifi or laptop required.

Post automatically merged: Feb 3, 2026

Will not be possible.

you can no run unsigned code from a switch cartdrige.

The saves are stored encrypted on the System NAND or User partition not at the cartdrige.


use JKSV which can backup any save to a cloud or webdav server.

Sorry, in another reply i specified that i am trying to transfer .sav files, not nintendo switch game save files, between a 3DS and a switch.

 

[impeeza]

Wouldnt this require wifi and a laptop? The end goal here is to transfer .sav files between a 3DS and a switch, so I am trying to find a solution that only needs those 2 devices. I happen to run into this problem frequently when I'm road tripping with my family. So I'd prefer a solution with no wifi or laptop required.

Post automatically merged: Feb 3, 2026

Sorry, in another reply i specified that i am trying to transfer .sav files, not nintendo switch game save files, between a 3DS and a switch.

your sav file from 3ds will not work on switch, unless your are running a emulator.

on a emulator like NSO the cartdrige have nothing to do,

by the way JKSV works on 3ds too.

 

[MateyMaterson]

your sav file from 3ds will not work on switch, unless your are running a emulator.

on a emulator like NSO the cartdrige have nothing to do,

by the way JKSV works on 3ds too.

Yes, I am running emulators on both. Isn't JKSV for 3DS games? I am referring to GBA games that use the .sav file type. I am running emulators on both the 3DS and the switch and need to transfer the save files back and forth.

 

[impeeza]

You are facing a X-Y paradigm you are trying to do something but you thing you need to do x and ask how to do x but you really need Y.

 

[MateyMaterson]

You are facing a X-Y paradigm you are trying to do something but you thing you need to do x and ask how to do x but you really need Y.

Yes, i wasn't being very clear in my original post sorry about that. But in my replies i think ive cleared it up? I am trying to play some GBA/GBC games, on emulators, on both the 3DS and the switch, while maintaining the same save file between the 2 devices. Please let me know if I am still not explaining myself properly

 

[Nephiel]

You could run homebrew FTP servers on either console, but then you'd also need a FTP client, and a WiFi to connect both devices to.

A smartphone with WiFi hotspot should work, and could also run some FTP client app to manage the files. It might not even need cellphone service to do it.

 

[kidkat210]

Yes, I am running emulators on both. Isn't JKSV for 3DS games? I am referring to GBA games that use the .sav file type. I am running emulators on both the 3DS and the switch and need to transfer the save files back and forth.

The dev of jksv ported it to switch as well. But moot point, you need a middle man of some sort no matter what. My 3ds homebrew knowledge is very rusty but if I remember correctly, the 3ds has an ftp client. So theoretically, you should be able to ftp the files between the 2 but that will require wifi of some form.