This is the approved revision of this page, as well as being the most recent.
The process to format an SD card to FAT32 is different for each operating system.
Optionally, if you have a 3DS with custom firmware, you can instead use GodMode9:
If you already understand how to use the tools in the above guides, here are direct links to their pages:
- Windows: SD Association Formatter + guiformat
- Mac: Disk Utility
- Linux: GParted + dosfstools