Source review: October 11, 2026. Follow the linked DSi Guide and DS-Homebrew documentation for your exact setup. Their supported installers and procedures can change.
Back up before formatting
SD formatting erases the selected device. Copy the whole card to a dated folder on another drive and verify that photographs, saves and configuration files can be read. Identify the card by its capacity and device name before opening a formatter. Do not select an internal computer drive just because it appears first in a list. Keep the original backup untouched while preparing a replacement card; it is both a recovery copy and a reference for the former directory layout.
Follow the project's platform-specific method
The DSi Guide provides separate Windows, Linux and macOS instructions. It distinguishes the filesystem and allocation settings needed by homebrew from a generic operating-system format. At the reviewed version, its Windows procedure uses sdFormatWindows and specifies FAT32 with forced 32 KiB clusters for cards of 64 GB or more. Use the complete instructions for your operating system, including any second formatting step, rather than combining individual commands from different platforms. The console's stock SD support and a particular homebrew's larger-card support are different claims.
Validate the storage before adding software
Run a full write-and-read test using the tool recommended for your computer in the DSi Guide. A card that lists folders successfully can still have defective or falsely advertised capacity. Record the tested capacity and result, and replace unreliable media before storing the only NAND backup on it. If a test fails, repeat with a known-good reader to distinguish a reader fault from a card problem. Repeatedly rewriting a failing card will not make a useful long-term backup.
Check names and extraction depth
The SD root is the top level visible when the card is opened. Copy the contents specified by the project's package rather than placing the entire extracted archive inside an extra directory. On Windows, display filename extensions so boot.nds is not actually boot.nds.nds. TWiLight Menu++'s DSi package uses its own root files and the _nds directory; a flashcard package is not automatically the correct package for the console's SD slot. Preserve unrelated photos and saves when refreshing application files.
Diagnose symptoms at the SD layer
If the console reaches Unlaunch but does not list SD applications, inspect formatting, card detection and the directory layout before considering internal storage recovery. Compare a clean card containing one documented test program with the old card. If the new card works, add saved configuration gradually until the problem returns. A missing menu file and a damaged NAND require very different actions. Keep screenshots of the visible error and a small directory listing for a support report, then retain the working card image and tested formatter settings as the new baseline.
Sources and project documentation
- DSi Guide: SD card preparation and validation
- DS-Homebrew: installing TWiLight Menu++ on DSi
- DSi Guide: Unlaunch SD-format symptoms
Continue with NAND and save preservation.