An NSP (Nintendo Submission Package) is a file format used for official digital software on the Nintendo Switch. : It mirrors official Nintendo eShop game packages.
Dr Kawashima's Brain Training Switch NSP: New Mental Challenges & How to Train
A “new NSP” claiming to be newer than 1.2.0 is —no further updates exist. Downloading such files risks installing unverified code.
Dr. Kawashima's Brain Training for Nintendo Switch: Is the NSP Worth It?
