Homebrew: Spotify 3ds

While a formal, official Spotify app never reached the Nintendo 3DS

Integration with third-party services

The Holy Grail: ThirdTube (The Closest We Have)

1. Download: Obtain the latest release of Splatube (typically a .3dsx file) from a reliable source like GitHub or the Universal-Updater store.
2. Transfer: Place the Splatube.3dsx file into the /3ds/ folder on your SD card.
3. Launch: Open the Homebrew Launcher on your 3DS and select Splatube.

For those who don't want to use the specific Spotify homebrew, the community has developed several high-quality music players that mimic the experience: spotify 3ds homebrew