2.ai
XO2.ai is a free Ultimate Tic Tac Toe AI game that runs entirely in your browser. Start on any square, send your opponent to the matching local board. Or let the AI move first in the settings menu. Win three local boards in a row to win the game.
Each move is made inside one of nine small tic tac toe boards. The cell you choose determines which small board your opponent must play in next. If that destination board is already won or full, your opponent can choose any open board.
Strong play means thinking one move ahead: win local boards, avoid sending the AI to immediate threats, and use free-choice moves to control the larger 3x3 board.
The AI evaluates the 9x9 position with an alphazero neural network with an estimated elo of 2000 and searches hundreds to thousands of possible continuations before replying. Use fewer visits for faster casual games or increase visits for a tougher challenge.