Would it be possible to build a .nds game as a cia?

Unfortunately, NDS games are designed to only launch from the cartridge slot. It is therefore impossible to make them into an installable CIA file.
However, workarounds exist. The best, most stable one is to buy a flashcart for $8-20. Flashcarts can pretend to be a cartridge and natively run your dumped games. If you do not want to use money, the next best option is an app called TWiLightMenu. Although slower and not as stable, this app will let you run NDS games for free on your 3DS. The above link (NDS Forwarder CIAs for your HOME Menu) is quite old, and I recommend you use TWiLightMenu instead.

Since DSiWare never launches from cartridge, does that mean there's another .nds subformat for that? Might be worth looking into as an intermediate step towards CIAs.

Since DSiWare never launches from cartridge, does that mean there's another .nds subformat for that? Might be worth looking into as an intermediate step towards CIAs.

DSiWare is distributed by Nintendo as CIAs on the 3DS and as .app files on the DSi. The 3DS .cia file contains the .app. A .app file is exactly the same format as a .nds file, except renamed.
The reason that DSiWare .apps are installable and regular .nds games are not is that .nds games are hardcoded to read from the cartridge slot, whereas DSiWare apps are designed to be run from the console.

It is possible to convert a DSiWare .app to a 3DS-installable .cia using simple tools. It is not possible to do that with a regular .nds game; however, it is possible to run them using the methods I listed above. In particular, TWiLightMenu will re-route all (or many) of the calls done by the game from the cartridge slot to the SD card.

Since DSiWare never launches from cartridge, does that mean there's another .nds subformat for that? Might be worth looking into as an intermediate step towards CIAs.

DSiWare is distributed by Nintendo as CIAs on the 3DS and as .app files on the DSi. The 3DS .cia file contains the .app. A .app file is exactly the same format as a .nds file, except renamed.
The reason that DSiWare .apps are installable and regular .nds games are not is that .nds games are hardcoded to read from the cartridge slot, whereas DSiWare apps are designed to be run from the console.

It is possible to convert a DSiWare .app to a 3DS-installable .cia using simple tools. It is not possible to do that with a regular .nds game; however, it is possible to run them using the methods I listed above. In particular, TWiLightMenu will re-route all (or many) of the calls done by the game from the cartridge slot to the SD card.

Makes sense, thanks. So that basically means converting .nds into .app requires generating a patch that hardcodes what TWiLightMenu does in memory...

Makes sense, thanks. So that basically means converting .nds into .app requires generating a patch that hardcodes what TWiLightMenu does in memory...

Exactly! And at that point, it is easier to use TWiLightMenu for all games, rather than to develop a patch for each separate game.

Great guide - thank you - any way to dump installed games from an SD card to .cia format on a computer using a command line tool or something like that? I have a 64GB SD card pre-installed with a bajillion games but it is so full that dumping the .cia files with Godmode9 sounds like a chore...

Makes sense, thanks. So that basically means converting .nds into .app requires generating a patch that hardcodes what TWiLightMenu does in memory...

Exactly! And at that point, it is easier to use TWiLightMenu for all games, rather than to develop a patch for each separate game.

What I was thinking is, since TWiLightMenu is capable of doing that in memory, it might be possible to create that patch using a generic script that performs the same changes but hardcoded. I'm not very familiar with the .xdelta format's structure or how exactly TWiLightMenu works internally though, so I have no idea how easy or hard something like that would be to auto-generate.

hello, Ive recently tried a method of building a cia from 3ds but, when i loaded the game, all my saves were gone. This game is Legend Of Zelda Majoras Mask.

hello, Ive recently tried a method of building a cia from 3ds but, when     
i loaded the game, all my saves were gone. This game is Legend Of 
Zelda Majoras Mask.

Try using Checkpoint to dump your saves.

hello, Ive recently tried a method of building a cia from 3ds but, when i loaded the game, all my saves were gone. This game is Legend Of Zelda Majoras Mask.

Save files need to be dumped separately. This is also true for extdata. As @Hypnotron mentioned, Checkpoint is a tool that helps with both.

Does anyone know what's the difference between Build CIA (standard) and Build CIA (legit) (in Dumping a system title as a .cia file)?

A legit cia refers to a cia that has a "universal" signature. That means it can be played even on a stock system. Unfortunately, building a legit .cia only works for titles that have been universally signed by Nintendo, i.e. games that came pre-installed on the system when you bought it.
A standard cia is just a normal installable game or application.
It is usually recommended to simply build a standard cia, as legit cias only work for a small number of apps and there isn't a point in installing them, as you need CFW to do that in the first place.

Source? 🙂

Does anyone know what's the difference between Build CIA (standard) and Build CIA (legit) (in Dumping a system title as a .cia file)?

A legit cia refers to a cia that has a "universal" signature. That means it can be played even on a stock system. Unfortunately, building a legit .cia only works for titles that have been universally signed by Nintendo, i.e. games that came pre-installed on the system when you bought it.
A standard cia is just a normal installable game or application.
It is usually recommended to simply build a standard cia, as legit cias only work for a small number of apps and there isn't a point in installing them, as you need CFW to do that in the first place.

Source? 🙂

Sorry, don't have a source, just plenty of experience in the field. I'm quite certain this is correct, but do correct me if im wrong 😛

Question. I have the latest Luma CFW on 11.15
I am trying to randomize Pokémon y from my physical cart using PK3ds. Which of these do I need to follow to use PK3ds? Is it “extracting romfs from a 3ds game cart”?

Question. I have the latest Luma CFW on 11.15 I am trying to randomize Pokémon y from my physical cart using PK3ds. Which of these do I need to follow to use PK3ds? Is it “extracting romfs from a 3ds game cart”?

Yes, exactly. You will need both RomFS and ExeFS for pk3DS, it seems :)

Hi. I'd like to upscale Pokémon Omega Ruby and Alpha Sapphire's textures. I'd prefer to dump all of their textures at once, rather than playing the game through the Citra emulator and dumping textures manually.

Is extracting the RomFS using a physical Nintendo 3DS the only way to dump all of the textures at once? Would I be able to modify the dumped texture files after or would a post process be required?

@lucasbrown

Hi. I'd like to upscale Pokémon Omega Ruby and Alpha Sapphire's textures. I'd prefer to dump all of their textures at once, rather than playing the game through the Citra emulator and dumping textures manually.

Is extracting the RomFS using a physical Nintendo 3DS the only way to dump all of the textures at once? Would I be able to modify the dumped texture files after or would a post process be required?

You don't have to extract them on the 3DS. If you have the .3ds or .cia file on your PC, try using NINFS :)
You will, however, need the arm9 bootrom and seeddb from your 3DS - check the NINFS' README.md file for instructions on that.
If you don't want to use NINFS, then you can simply follow one of the sections above, selecting all of the RomFS files you need and dumping them at once.

I don't know what format Pokémon textures and models are stored in. The specifics will be different for every game. Try extracting them first and, if they are encoded in some way, look online for tools developed for your specific games.

@PixelSergey

You don't have to extract them on the 3DS. If you have the .3ds or .cia file on your PC, try using NINFS :)
You will, however, need the arm9 bootrom and seeddb from your 3DS - check the NINFS' README.md file for instructions on that.
If you don't want to use NINFS, then you can simply follow one of the sections above, selecting all of the RomFS files you need and dumping them at once.

Excellent, thank you!

I don't know what format Pokémon textures and models are stored in. The specifics will be different for every game. Try extracting them first and, if they are encoded in some way, look online for tools developed for your specific games.

Understood. Thanks again.

@SleepyFishYT

how to convert cxi to zip ?

A .cxi file essentially contains the executable portion of a .3ds file. You can't convert it directly to a .zip.
The instructions under Extracting RomFS from a .cia/.3ds/.nds file should apply to a .cxi file as well. That should let you extract all the files.

Can't see search titles option, I can only see title manager

Can't see search titles option, I can only see title manager

I am not sure what causes this, but your godmode9 might be too old/outdated. Try updating it and following the instructions again carefully.

Hmm, I can understand that I can use GodMode9 on my 3DS to dump DSiWare titles as either a .app or a .nds format, but how do I backup DSiWare save files? These are important, too. I want to keep on playing them with the save in Twilight Menu rather than just starting over.

Hmm, I can understand that I can use GodMode9 on my 3DS to dump DSiWare titles as either a .app or a .nds format, but how do I backup DSiWare save files? These are important, too. I want to keep on playing them with the save in Twilight Menu rather than just starting over.

A save manager like Checkpoint should be able to do this

What do I do after I dumped files from an cxi file.
I simply want to install the game, so I guess I have to create a cia file now.
Can anyone tell me how?

Edit: Nevermind. I found, that you can simply build a cia from the cxi.

@MakashiDev I have the same problem as this guy, and I just updated Godmode9.

@MakashiDev @Pikrioling Taking a wild guess here, maybe it's been renamed to "Search for files" in recent versions?

@ehx-v1 actually, you press Open Title Manager, then select the title you want to do stuff with by pressing A, select Open Title Folder, selcet the .tmd file and then press TMD File Options.... There press Mount CXI/NDS to drive, enter path go to the file/folder you want to copy, press A (or R + A if you're copying a folder) and select Copy to 0:/gm9/out. The Romfs should be there after it's done.

@Pikrioling Ah, so that means "Open Title Manager" is the new "Search titles".

I am not sure what causes this, but your godmode9 might be too old/outdated. Try updating it and following the instructions again carefully.

I am encountering the same issue as the person above, and I double checked and my Godmode is up to date. Perhaps there's been a mistake by whoever writes the guide.

@AlcalineAlice It seems that Godmode9 did some restructuring and the guide is slightly out of date now. Check the discussion right above your comment.

Is there a way that I can extract the ROMs from the CIA files of my legal virtual console GB/GBC games?