The location of the SD card slot and the type of SD card that is accepted depends on the model of your 3DS. More information can be found on Nintendo’s official support page.
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The 3DS can read SD cards of any capacity (even those larger than 32GB), but the card must be formatted as FAT32 (not exFAT or NTFS). You can use one of the following tools to format your SD card, depending on your operating system: Windows, macOS, Linux.
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The 3DS can read SD cards of any capacity (even those larger than 32GB), but the card must be formatted as FAT32 (not exFAT or NTFS). You can use one of the following tools to format your SD card, depending on your operating system: Windows, macOS, Linux. SD cards larger than 128GB are not recommended due to known issues with custom themes and GBA/DS graphics.
To follow this guide, you’ll need an SD card with a capacity of at least 2GB.