Do You Need a Nintendo 3DS to Play 3DS Games? Yes.

Yes. Nintendo 3DS cartridges only work on 3DS-family hardware: 3DS, 3DS XL, 2DS, New 3DS, New 2DS XL, New 3DS XL. They will not run on DS, DSi, Wii U, Switch, or any non-Nintendo device.

Why Not Other Systems?

• Different architecture: 3DS uses ARM11 + custom GPU (PICA200). DS uses ARM9/ARM7. Incompatible instruction sets.
• Encryption: 3DS carts use AES encryption with per-console keys. No software emulator on DS/DSi can decrypt them.
• Physical shape: 3DS cartridges have a notch preventing insertion into DS slots.

What About Emulation?

• Citra (PC/Android): Excellent compatibility, upscaling, multiplayer. Requires decent hardware (OpenGL 3.3+, 4GB+ RAM).
• Legal requirement: You must dump games from your own cartridges using a hacked 3DS (GodMode9). Downloading ROMs is piracy.
• Performance: Most titles run full speed on modern mid-range PCs/phones.

If you want to play 3DS games, buy a 2DS (cheap, durable) or use Citra with legally dumped games. There's no shortcut.