This paid service lets Nintendo Switch owners enjoy online multiplayer gaming as well as a dedicated smartphone app that connects to your Nintendo Switch system and helps you connect with friends for online play sessions.
Enjoy online services for free until the paid service’s official launch in 2018.
Pricing
Classic Game Selection
Subscribers will get to download a compilation of classic titles with added online play, such as Super Mario Bros. 3, Balloon Fight and Dr. Mario.
After the free-trial period, most games will require a paid online service subscription from Nintendo in order to play online.
This service is only for Nintendo Switch. It does not affect online play or features for the Wii U or Nintendo 3DS family of systems.
More: http://www.nintendo.com/switch/online-service/