Rules
When does a Reversi game end?
The short answer
The game ends the moment neither player has a legal move. Most games reach that point when the board is full after 60 moves. Some stop earlier, either because both players are stuck with squares still empty, or because one colour has been flipped off the board entirely.
There is only one ending condition, and everything else is a consequence of it. Neither player has a legal move, so play stops and you count the discs. Three different-looking finishes come out of that single rule.
Ending 1: the board fills up
Four discs are on the board at the start, leaving 60 empty squares. A game that uses every one of them runs to exactly 60 moves, 30 each. This is by far the most common ending.
Black 34, White 30, adding to 64. Nobody has a move because there are no empty squares left to play on.
Ending 2: both players are stuck
A board with empty squares on it can still be finished. If every remaining empty square would flip nothing for either colour, neither player can move and the game is over. It usually happens when the last few gaps are tucked away in a region that neither colour can reach.
Here the game ran to 59 moves and stopped with 1 square empty. White wins 39 to 24. In tournament play the empty square is added to the winner's total, so the recorded score becomes 40 to 24. How scoring handles this.
Ending 3: a wipeout
Every legal move needs one of your own discs to close the line. Flip your opponent's last disc and they have nothing to close with, so they can never move again and the game ends on the spot.
This can happen absurdly early. The shortest possible game of Othello is 9 moves long, and the one below is an example of it.
Black 13, White 0, 51 squares empty, and Black wins. Awarding every empty square to the winner makes it 64 to 0, which is the largest score the game allows.
What does not end the game
- One player passing. A pass just hands the turn back. The game continues as long as the other player has a move. The passing rule.
- Running out of discs in the box. On a physical set the opponent lends you discs. Nothing about the game stops.
- A big lead. There is no mercy rule and no early finish for a lopsided position. A 50 to 4 lead has been overturned before.
- Time. A clock running out ends a tournament game, but that is a tournament rule rather than a rule of Othello.
Counting the last few moves
Once fewer than about a dozen squares are empty, the ending can be worked out exactly rather than guessed. Who is forced to move last into each empty region is called parity, and it often decides the whole game. Parity and endgame strategy cover it.
Play one out
Take a game to the finish on the board on this site and see which of the three endings you get. Set the computer to Hard and it will solve the last dozen squares exactly, which is a good way to watch how much a finish can swing.
Related: scoring, the complete rules and how many discs a game uses.
Frequently asked questions
When does an Othello game end?
The moment neither player has a legal move. Usually that is when all 64 squares are full after 60 moves, but a game can also stop with squares still empty, or as soon as one colour is wiped off the board.
How many moves are in a full game of Othello?
Sixty. Four discs are already on the board at the start, so 60 empty squares remain, and a game that fills the board uses all of them. Passes do not count as moves.
Does the board have to be full for the game to end?
No. If neither player can flip anything, the game is over whatever the board looks like. Empty squares at the end are awarded to the winner in tournament play. Scoring.
What happens if a player loses all their discs?
The game ends immediately. With no discs on the board there is nothing to close a line with, so that player can never move again. This is called a wipeout and is scored 64 to 0 in tournaments.
Can the game end while both players still have moves?
No. As long as either player has one legal square, play continues. Resigning ends a tournament game with a 64-0 score against the player who resigned, but that is a tournament convention rather than a rule of the game.