https://www.cnet.com/news/nintendo-switch-online-is-officially-live-what-you-need-to-know/

Playing Nintendo Switch games online is no longer free. The company officially launched its Nintendo Switch Online service -- complete with retro games and updates to the Nintendo Switch smartphone app.

The paid online service costs $3.99 a month, $7.99 for a three-month period or $19.99 a year -- and is now required for Switch owners who want to play multiplayer games over the internet. In other words, the service is effectively putting parts of major titles like Splatoon 2 and Mario Kart 8 behind a paywall.