This paper defines as downloadable content that:

To utilize a Mario Kart 8 Deluxe DLC NSP file, players rely on specific software environments:

A heavy-weight favorite from the GameCube era. Wiggler: The iconic angry caterpillar from Mario Kart 7. Kamek: The magical Magikoopa making his console debut.

Downloading NSP files from third-party websites violates Nintendo’s Terms of Service and copyright laws. Legally, users must dump their own purchased DLC from their personal Switch console.

Because the Booster Course Pass was a purely digital release, its files exist natively as NSPs. Why Modders Look for DLC NSPs

The Mario Kart 8 Deluxe Booster Course Pass DLC is a must-have for fans of the series. With 48 new tracks, 8 new characters, and ongoing updates, there's plenty of new content to enjoy. And with exclusive courses like Toad's Treasure Trove, Yoshi's Island, and DK's Jungle Adventure, you'll have access to unique racing experiences that can't be found anywhere else.