Short answer: Yes, it was completely free—no subscription required—but the service was officially discontinued in 2014.
When Nintendo launched the Nintendo Wi-Fi Connection (WFC) alongside the Nintendo DS in 2005, it broke new ground. Unlike Xbox Live or PlayStation Network at the time, WFC required no paid membership, no friend codes for every single game (though some titles used them), and no complex setup. You simply connected your DS to a Wi-Fi network, inserted a compatible game, and jumped online. Titles like Mario Kart DS, Pokémon Diamond/Pearl/Platinum/HeartGold/SoulSilver/Black/White, Animal Crossing: Wild World, and Metroid Prime Hunters thrived on this infrastructure.
On May 20, 2014, Nintendo permanently shut down the WFC servers for all DS and Wii games. This wasn't a temporary outage—it was the end of official online play for an entire generation of handheld and console titles. Since then, popping in a DS cart and selecting "Nintendo WFC" leads only to error codes.
The community refused to let online DS gaming die. The most prominent replacement is Wiimmfi, a fan-run server network that restores online functionality for dozens of games, including:
164.132.44.106, secondary: 1.1.1.1)Other projects like AltWFC and custom DNS services cover additional titles not supported by Wiimmfi.
If you have two DS systems within ~30 feet, local multiplayer works natively—no internet, no mods, no servers required. This is how the DS was originally designed to connect, and it remains fully functional today.
Bottom line: Official online is gone. Wiimmfi is free, community-run, and requires modding. Local wireless works out of the box.