Nine boards, one game
Win three small boards in a line to win the game. The catch: the cell you play decides which board your opponent must play in next.
Ultimate Tic-Tac-Toe adds one rule to a game everyone considers solved: the cell you take sends your opponent to the matching board. It spread over the internet from 2013 and has no single inventor.
The board is a three-by-three grid of small tic-tac-toe boards — nine boards, eighty-one cells. X moves first. Winning a small board with three in a line claims it, and claiming three small boards in a line wins the whole game. That much is just tic-tac-toe twice over. The rule that makes it a game is the sending rule below, and it is the only one worth memorising.
The cell you play in decides the board your opponent must play in next. Take the top-right cell of any board, and your opponent must play somewhere in the top-right board. Take the centre cell, and they are sent to the centre board. So you are never simply choosing the best square in front of you. Every move is two decisions at once: what it does for you here, and where it puts your opponent. Beginners lose because they only make the first decision. On Cognivo, hovering a cell outlines the board it would send your opponent to, so you can see the second decision before you commit to it.
If you are sent to a board that is already finished — won by either side, or drawn — you are not stuck. You may play in any unfinished board instead. That is a free choice, and it is the most valuable thing you can be handed in this game. Which means the reverse is the thing to avoid: sending your opponent to a finished board hands them the run of the whole position. Late in a game, when several boards are decided, half the skill is counting which cells still send somewhere and which have quietly become free passes.
Three claimed boards in a line — across, down, or diagonally — wins immediately. A small board with every cell filled and no three in a line is drawn, and a drawn board counts for neither side; it is simply out of play and sends anyone pointed at it somewhere else. The whole game is drawn when every board is decided and no side holds three in a line. Cognivo shows the running count of boards held by each side beside the board, because the score of a position this cluttered is genuinely hard to read at a glance.
The commonest beginner mistake is treating each small board as its own game and playing it out to win. It costs games, because a small board is not the prize — it is one of nine cells in the only board that matters. So losing a small board on purpose is a normal move here. If giving up the bottom-left board keeps your opponent out of the centre for three turns, the trade is usually good. Ask what a move does to the big board first, and what it does to the small one second.
The centre board sits in four of the eight winning lines — more than any other — so it is the most valuable board to hold, exactly as the centre square is in ordinary tic-tac-toe. The centre cell of each board is valuable for a different and more interesting reason: playing it sends your opponent to the centre board. That makes centre cells the standard way to fight for the centre without playing there yourself, and it is why strong games so often circle the middle for the first dozen moves.
The move that actually decides most games is the one creating two threats your opponent cannot answer together. It happens on both levels. On a small board it is ordinary tic-tac-toe: a fork with two ways to make three. On the big board it is the same shape one level up — reaching a position where you threaten to claim either of two boards that each complete a line. Because claiming a board takes several moves rather than one, a big-board double threat is something you build over many turns, and it is usually invisible to an opponent who is watching only the board in front of them.
Learn Ultimate Tic-Tac-Toe: the full lesson, with moves to try on the board →