PyChess

PyChess is a free, open-source chess server built for playing chess variants from around the world. Maintained by developer gbtami and powered by Fairy-Stockfish (a Stockfish fork that supports dozens of variant rulesets), PyChess lets you play against other people or the engine across more than 30 different games, all from your browser.

The variant library is impressively deep. You can play Southeast Asian classics like Makruk, Sittuyin, and Ouk Chaktrang. East Asian games like Shogi, Xiangqi, and Janggi are fully supported with proper piece sets and boards. Western variants include Crazyhouse, Atomic, King of the Hill, Duck Chess, and several Capablanca-style extended board games. More modern creations like Orda Chess, Synochess, Shinobi, and Empire round out the collection. Each variant has its own learn page explaining rules and strategy.

Beyond just playing, PyChess offers tournaments, puzzles, game analysis with Fairy-Stockfish, a board editor, and a TV feature for watching live games. The interface is heavily inspired by Lichess, with clean design and customizable board and piece themes. Authentication works through Lichess, Google, or Discord accounts. The entire project is open source under the AGPL-3.0 license, with 53 contributors on GitHub and an active Discord community.

PyChess is completely free with no ads or premium tiers. If you are interested in chess variants beyond standard chess, it is one of the best places to play online.