Can You Install Apps on Nintendo DSi? Understanding the Limitations

No. The DSi runs a closed proprietary OS. There is no App Store for third-party applications (unlike smartphones).

What You Can Run

• DSiWare: Official Nintendo downloadable games/apps (Shop closed 2017; purchased titles redownloadable).
• DS Cartridges: Retail games.
• Homebrew (via Exploit): Memory Pit (DSi Camera exploit) or Flipnote Studio Lenny exploit allows running .nds homebrew from SD card. Emulators (NES, GB, GBA), media players, DSLinux. Requires technical steps; bricks possible if wrong.

Limitations

Low RAM (16MB), ARM9/ARM7 CPUs, no GPU—can't run modern apps (YouTube, Discord, browsers).

For apps, use a smartphone. For DSi, enjoy the games and Flipnote Studio.