Nintendo will end its Nintendo Wi-Fi Connection service for Wii and Nintendo DS owners on May 20, according to a post on Nintendo's website. This means Wii and DS owners will no longer be able to use online play, matchmaking, or leaderboards across any of the two platforms' titles.
"As of May 20, 2014, certain online functionality offered through Nintendo Wi-Fi Connection will no longer be accessible," states the announcement, which also features the full list of games affected. "The discontinued services include online play, matchmaking and leaderboards for many Wii, Nintendo DS and Nintendo DSi games."
While there weren't too many Wii and DS titles that utilized online play, arguably the biggest ones did. That includes Mario Kart DS and Mario Kart Wii, Super Smash Bros. Brawl, and a whole lot of Pokemon games. Playing these games on your Wii U and 3DS using their backwards compatibility features won't work, either.
The discontinuation of the Nintendo Wi-Fi Connection service will not affect the Wii Shop Channel and Nintendo DSi Shop, both of which will continue to offer games and services. The Internet Channel, video-on-demand services, and DS/DSi Browsers will continue to function past the May 20 cutoff date, as well.