Lichess

Lichess is a free, open-source online chess server for playing and studying chess. It offers game analysis powered by the Stockfish engine, puzzles, tournaments, and learning resources. Users can create lobby games, participate in arena or Swiss tournaments, and engage in simultaneous exhibitions. The platform includes various puzzle types like Puzzle Themes, Puzzle Streak, and Puzzle Storm. Learning resources cover chess basics, practice modules, coordinate training, and studies. Lichess also provides features for watching broadcasts, Lichess TV, and current games.