OpeningTree is described as 'Consolidated view of all your chess games from chess.com, lichess, grandmaster games or custom pgn. Prepare against your opponents by analyzing at their games and see which openings work for you' and is an game in the games category. There are more than 10 games similar to OpeningTree for a variety of platforms, including Windows, Linux, iPhone, iPad and Mac apps. The best OpeningTree alternative is Lichess, which is both free and Open Source. Other OpeningTree like games are Chess.com, KNights, WintrChess and ChessMD.