What is the NDS file format?
The .nds extension (short for Nintendo Dual Screen) is used by Nintendo DS game ROM image files. A single .nds file stores the ROM flash data image obtained from an original Nintendo DS game cartridge - a raw binary dump of the cartridge's flash memory. The file header encodes a 12-byte game title at offset 0x00, a 4-byte game code at 0x0C, and the Nintendo logo bitmap the hardware uses to verify the boot process.
.nds files allow users to play Nintendo DS games on a computer or mobile device using an emulator. They are also used for storing homebrew games, which can be played on real hardware via flashcarts. Companion .sav files hold save data; IPS patches are commonly applied for fan translations. The format debuted with the Nintendo DS in 2004, succeeding Game Boy Advance cartridges.
Security & safety
RISK: MEDIUMThe ROM data itself is inert game code that only runs in an emulator, but two real concerns apply. Legal: downloading ROMs of games you don't own is copyright infringement in most countries - the lawful path is dumping your own cartridges or playing homebrew/freeware. Source safety: 'ROM sites' are notorious for fake download buttons, ads and bundled malware; download only the EMULATOR from its official site (melonDS, DeSmuME, OpenEmu) and avoid sketchy portals. Flashcarts that load .nds on real hardware are legal to own but commonly used for piracy.
Format details
in a nutshellPrograms that open NDS files
Windows3 apps
DeSmuME
Open-source File > Open ROM and select the .nds. Long-standing, broadly compatible DS emulator. 
MelonDS
Open-source File > Open ROM and pick the .nds. Best accuracy/speed; supports local wireless & Wi-Fi emulation.
RetroArch
Open-source Load the .nds with a DS core (melonDS or DeSmuME). Adds gamepad/shader support. 
macOS3 apps
OpenEmu
Open-source Drag the .nds into the OpenEmu library; it uses a DS core automatically. Native Mac front-end. 
Linux2 apps
Android3 apps
melonDS (Android)
Open-source Install the melonDS Android build, point it at the .nds and play with on-screen touch controls.
DraStic DS Emulator
Paid Fast, low-end-friendly DS emulator; load the .nds. Officially discontinued but community 'revived' builds exist. Technical details
deep spec| File type | Raw binary Nintendo DS cartridge ROM dump |
| Header size | 512 bytes at file offset 0x000 |
| Game title field | 12-byte ASCII string at file offset 0x000 (null-padded to fill all 12 bytes) |
| Game code field | 4-byte ASCII identifier at offset 0x00C; encodes game ID, platform code (D for DS), and region |
| Processor sections | Separate ARM9 (main CPU) and ARM7 (sub-CPU) executable code regions, each with its own entry point |
| Embedded file system | Nitro File System (NitroFS) for game asset storage; NARC archives commonly used within |
| Boot validation | Nintendo logo bitmap and CRC stored in header; DS hardware verifies CRC before allowing boot |
| ROM capacity range | 8 MB (64 Mbit) to 512 MB (4 Gbit) depending on cartridge mask ROM size |
| MIME type | application/octet-stream |
| Byte order | Little-endian throughout |
| Save data | External .sav or .srm file holds save state; type (EEPROM, Flash, or FRAM) varies by game |
| DSi and 3DS compatibility | .nds ROMs run in NDS backward-compatibility mode on DSi, DSi XL, and Nintendo 3DS family hardware |
| Flashcart loading | Loadable on original DS hardware via flashcart devices such as R4, Acekard 2i, and DSTT |
| Patch support | IPS and xdelta patches applied directly to the ROM binary for fan translations and ROM hacks |
| Released | 2004 (Nintendo DS launch) |
| Specification | problemkaputt.de |
NDS conversions
Community Q&A
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