Online - fairy-stockfish/Fairy-Stockfish GitHub Wiki
Fairy-Stockfish can be used on various websites online, either as the official playing and analysis engine of the site, or as a bot interacting with it. If you want to experiment with custom variants, Fairyground might be a good place to start.
Fairyground
Fairyground (Fairy-Stockfish playground) serves as a playground to try out Fairy-Stockfish online with custom variants, enabling game play and interactive analysis.
Lichess
Lichess uses Fairy-Stockfish for play against the computer in variants and for server-side analysis. When it is online you can also play against the official Fairy-Stockfish bot on lichess https://lichess.org/@/Fairy-Stockfish, which uses the latest NNUE networks for variants. You can also set up your own lichess bot with Fairy-Stockfish if you like.
Pychess
On Pychess you can play various chess variants against Fairy-Stockfish, e.g., Xiangqi, Shogi, Makruk, Janggi, and more. Pychess Alt supports additional variants such as torpedo chess as well.
Lishogi
Lishogi uses Fairy-Stockfish for play against the computer from custom positions and for local analysis. Besides that, there is also an official Fairy-Stockfish bot on lishogi https://lishogi.org/@/Fairy-Stockfish, which uses NNUE evaluation.
Playstrategy
Playstrategy uses Fairy-Stockfish for game play and server-side analysis in various games.
Xichess
Xichess is a Xiangqi website using Fairy-Stockfish for game play and analysis.
FICS
To play bughouse against Fairy-Stockfish on FICS, you need to set up Fairy-Stockfish with XBoard/Winboard zippy mode.