DSi Game File Extension / Format

DSi games don’t have a public file extension. They’re stored in a proprietary Nintendo format:

• Inside a “title” folder (contains game data, ticket, banner).
• Which contains a “rom” or “content” folder with the actual game binary.
• Often distributed as a .zip or .cia (CTR Importable Archive) for homebrew/emulation.

On a hacked DSi/3DS, you’ll see .cia files for installation. Retail cartridges use a proprietary ROM format with no standard PC extension.