How do you play Reversi?

The game starts with four discs in the middle: White on d4 and e5, Black on d5 and e4, and Black moves first. On your turn you place one disc so that it traps at least one line of your opponent's discs between the new disc and another of yours, across a row, a column or a diagonal. Every trapped line flips to your colour, in all directions at once. If you have no such move you pass, and the game ends when neither side can move. The side with more discs wins; equal counts are a draw, and empty squares are not added to either score. Squares are named by a file letter a to h from left to right and a rank number 1 to 8 from top to bottom, so d3 is the fourth column, third row.

Can I play Reversi against the computer here?

Yes. Choose Computer, pick Black or White and a level. Easy looks one move ahead. Medium looks up to 3 single moves ahead within 2,000 positions, and Hard up to 8 within 200,000 positions; if the budget runs out first, it keeps the best move from the deepest search it finished. It scores a position by square values that prize corners and avoid the squares next to an open corner, by how many moves each side has, and by disc count once 12 or fewer squares are empty; a finished game counts as a win or a loss. It runs in a background worker, gives the same reply to the same position at the same level, and its move appears no sooner than 300 ms after yours. It is a heuristic, not a perfect player. If the worker cannot start, fails or has not answered within 4 seconds, the page plays a one-move lookahead instead and says so under the status line. A friend plays on this same device; there is no online play against another person.

What happens when a player has no legal move?

That player passes and the other side moves again. The page does this for you: the status line says who passed, and the move list records it as pass. When neither side has a legal move, for example because every square is full or one colour has no discs left, the game is over and the final disc count is shown. The Worked cases list has two games you can load: A forced pass, where Black has no move after eight moves, and Shortest finish, nine moves after which White has no disc left. An exhaustive check of all 390,216 eight-move games from the start confirms none of them has ended, so nine moves is the fewest a game can take.

Is Reversi the same as Othello?

This page uses the board, starting position and flipping rules of the modern game also sold as Othello: an 8 x 8 board, the four centre discs placed crosswise, Black moving first, passes when a side cannot move, and the end when neither can. It is not connected with that brand. Here the score is the plain disc count at the end, and empty squares are not awarded to the winner.

Can I take back a move or look back through the game?

Undo takes back one move between two players, along with any pass it forced. Against the computer it takes back your last move and the computer's reply; if the computer is still thinking, Undo cancels its search and takes back your move, and the cancelled search never changes the board. The move list below the game is a set of buttons: pick any move, or use Start, Back and Forward, to see the board after it. Replay only shows earlier positions and cannot play from them; Live position brings back the current board.

How do I save, export or import a game?

The game and your settings are saved in this browser after you make a move or change a setting, and come back when you return. Copy record puts the game on your clipboard as plain text, and Download record saves the same text as reversi-game.txt. The record names the coordinates and the start, lists the moves as numbered Black and White pairs with pass where a side could not move, and ends with the result. Import accepts that record, pasted or opened as a .txt file, or a bare list of moves such as d3 c5 f6 or d3c5f6, with passes written or left out. Every move is replayed and checked; if any move is illegal or unreadable, the error names it and your current game stays on the board. Against the computer, you take the side to move in the imported game.

Can I play with a keyboard or on a phone?

Yes. Tab to the board, move between squares with the arrow keys, use Home and End to jump to the ends of a rank, and press Enter or Space to place a disc. With hints on, every legal move is also a button under the board, and you can always type a square such as d3 and press Play. On narrow screens the board fills the width, with the rank numbers and file letters drawn inside the edge squares, so each square is 44 pixels on a 390-pixel-wide phone, and the other buttons and fields are at least 44 pixels tall. On narrower phones the squares are smaller than 44 pixels; there the legal-move buttons, shown while hints are on, and the Type a move field with its Play button are the 44-pixel alternatives to tapping a square. A text description under the board lists every disc and the last move.

Reversi

Play Reversi, the 8 x 8 disc-flipping game, on one device: pass it between two players, or take Black or White against the computer at Easy, Medium or Hard. With hints on, dots mark every legal move and each one is also a button under the board; a side with no move passes automatically and the pass is written into the move list; the game ends when neither side can move. Undo takes back your move and the computer's reply, the move list replays any earlier position, and the whole game copies or downloads as a plain-text record that this page imports again, as it does a pasted list of moves such as d3 c5 f6. The game is saved in this browser once you play or change a setting, and your moves are not sent anywhere.

Your game

Opponent

You play

Computer level

Medium looks up to 3 moves ahead within 2,000 positions.

Show legal moves

Loading the board and any saved game.

boardBlack to move

Arrow keys move between squares, Home and End jump along a rank, Enter or Space plays a disc.

Text equivalent: Starting position. Black discs (2): d5, e4. White discs (2): d4, e5. 60 empty squares.

Discs: Black 2 · White 2

To move: Black (you)

Legal moves: c4, d3, e6, f5

Moves: 0

Move list and replay

Pick any move to see the board after it. Replay only shows earlier positions; press Live position to play on.

Showing the live position after 0 moves.

No moves yet.

Import a game record

Paste a record copied or downloaded from this page, or a plain list of moves such as d3 c5 f6 or d3c5f6. Passes may be written as pass or left out. The moves are replayed from the standard start and checked one by one; your current game stays unless the whole record is valid.

Game record to import

Open a .txt file

The record format

Reversi game record, format 1
Coordinates: files a to h left to right, ranks 1 to 8 top to bottom
Start: White on d4 and e5, Black on d5 and e4, Black moves first
Moves: 1. d3 c3 2. b3 b2 ... (pass where a side cannot move)
Result: recomputed from the moves when imported

Worked cases

Each result below is worked out by the same rules the board uses. Loading an example replaces the current game.

Openingstandard start, Black to move
legal: c4, d3, e6, f5
FlipBlack plays d3
flips d4: Black 4, White 1
A forced passd3 c3 b3 b2 f5 a3 a1 c1: eight moves in, Black has no legal move
Black has no legal move and passes; White plays on with e3 or f6
Shortest finishd3 c3 b3 d2 e1 d6 d7 e3 f4: nine moves, the fewest any game can take
White has no discs left; neither side can move: Black 13, White 0

Common questions

How do you play Reversi?: The game starts with four discs in the middle: White on d4 and e5, Black on d5 and e4, and Black moves first. On your turn you place one disc so that it traps at least one line of your opponent's discs between the new disc and another of yours, across a row, a column or a diagonal. Every trapped line flips to your colour, in all directions at once. If you have no such move you pass, and the game ends when neither side can move. The side with more discs wins; equal counts are a draw, and empty squares are not added to either score. Squares are named by a file letter a to h from left to right and a rank number 1 to 8 from top to bottom, so d3 is the fourth column, third row.
Can I play Reversi against the computer here?: Yes. Choose Computer, pick Black or White and a level. Easy looks one move ahead. Medium looks up to 3 single moves ahead within 2,000 positions, and Hard up to 8 within 200,000 positions; if the budget runs out first, it keeps the best move from the deepest search it finished. It scores a position by square values that prize corners and avoid the squares next to an open corner, by how many moves each side has, and by disc count once 12 or fewer squares are empty; a finished game counts as a win or a loss. It runs in a background worker, gives the same reply to the same position at the same level, and its move appears no sooner than 300 ms after yours. It is a heuristic, not a perfect player. If the worker cannot start, fails or has not answered within 4 seconds, the page plays a one-move lookahead instead and says so under the status line. A friend plays on this same device; there is no online play against another person.
What happens when a player has no legal move?: That player passes and the other side moves again. The page does this for you: the status line says who passed, and the move list records it as pass. When neither side has a legal move, for example because every square is full or one colour has no discs left, the game is over and the final disc count is shown. The Worked cases list has two games you can load: A forced pass, where Black has no move after eight moves, and Shortest finish, nine moves after which White has no disc left. An exhaustive check of all 390,216 eight-move games from the start confirms none of them has ended, so nine moves is the fewest a game can take.
Is Reversi the same as Othello?: This page uses the board, starting position and flipping rules of the modern game also sold as Othello: an 8 x 8 board, the four centre discs placed crosswise, Black moving first, passes when a side cannot move, and the end when neither can. It is not connected with that brand. Here the score is the plain disc count at the end, and empty squares are not awarded to the winner.
Can I take back a move or look back through the game?: Undo takes back one move between two players, along with any pass it forced. Against the computer it takes back your last move and the computer's reply; if the computer is still thinking, Undo cancels its search and takes back your move, and the cancelled search never changes the board. The move list below the game is a set of buttons: pick any move, or use Start, Back and Forward, to see the board after it. Replay only shows earlier positions and cannot play from them; Live position brings back the current board.
How do I save, export or import a game?: The game and your settings are saved in this browser after you make a move or change a setting, and come back when you return. Copy record puts the game on your clipboard as plain text, and Download record saves the same text as reversi-game.txt. The record names the coordinates and the start, lists the moves as numbered Black and White pairs with pass where a side could not move, and ends with the result. Import accepts that record, pasted or opened as a .txt file, or a bare list of moves such as d3 c5 f6 or d3c5f6, with passes written or left out. Every move is replayed and checked; if any move is illegal or unreadable, the error names it and your current game stays on the board. Against the computer, you take the side to move in the imported game.
Can I play with a keyboard or on a phone?: Yes. Tab to the board, move between squares with the arrow keys, use Home and End to jump to the ends of a rank, and press Enter or Space to place a disc. With hints on, every legal move is also a button under the board, and you can always type a square such as d3 and press Play. On narrow screens the board fills the width, with the rank numbers and file letters drawn inside the edge squares, so each square is 44 pixels on a 390-pixel-wide phone, and the other buttons and fields are at least 44 pixels tall. On narrower phones the squares are smaller than 44 pixels; there the legal-move buttons, shown while hints are on, and the Type a move field with its Play button are the 44-pixel alternatives to tapping a square. A text description under the board lists every disc and the last move.

Standard Reversi rules on an 8 x 8 board: a disc must outflank at least one opposing disc in a straight line, every outflanked line flips, a side with no legal move passes, and the game ends when neither side can move, scored by disc count. The computer is a bounded heuristic that looks one move ahead on Easy and up to 3 or 8 single moves ahead on Medium and Hard, within a fixed number of positions, so it is not a perfect player and can be beaten.