For the Nintendo Switch, these files are digital "rips" of physical cartridges or eShop downloads. They typically come in two primary formats: These are direct dumps from physical game cartridges.
Nintendo maintains that downloading or distributing pirate copies of its games is illegal. They argue that even "abandonware" (games no longer sold) is protected by copyright. Nintendo Switch ROMs
The short answer is . In most jurisdictions, downloading ROMs from the internet is considered copyright infringement, even if you already own a physical copy of the game. For the Nintendo Switch, these files are digital