Legally, the most accepted way to use a ROM for personal emulation is to "dump" or "rip" it yourself from your own physical cartridge. Legitimate Alternatives and Game Overview
Users often find themselves in a cat-and-mouse game with Nintendo’s anti-piracy measures. Systems found running unauthorized software are frequently banned from online services, stripping the console of its multiplayer functionality and eShop access. Thus, the "free" game often comes at the cost of a gimped console and security risks. new super mario bros u deluxe download rom