NSP stands for . It is the official format used by Nintendo to distribute digital games, updates, and DLC via the eShop. When you buy Super Smash Bros Ultimate digitally, your Switch downloads a series of encrypted NSP files.
: If you legitimately bought the game via eShop and your download shows strange .part files (possible download manager glitch). Super Smash Bros Ultimate -NSP--Jogo Base-.part...
(Reddit, Discord, Twitter, Facebook group, forum), and confirm the post is not asking for or sharing pirated content, I can write a clean, safe, and useful version for you. NSP stands for