Downloading NSP updates for games you do not legally own constitutes copyright infringement and is illegal in most jurisdictions. However, extracting your own game updates from your own Switch console for backup purposes falls under the umbrella of preservation. Tools like nxdumptool allow users to create their own NSP backups of their legally owned games and updates.
(for legally owned copies):
An "NSP update" is essentially a patch file. It does not contain the full game; rather, it contains modified files intended to overwrite or supplement the base game data. These updates serve several purposes: mario kart 8 nsp update
It is highly recommended to remove any existing update data for the game via the official System Settings -> Data Management menu before installing a new update NSP to prevent version conflicts. Downloading NSP updates for games you do not
Always support developers by purchasing your games and DLC officially. (for legally owned copies): An "NSP update" is