Reversi Rules, Explained

Reversi has one core rule: trap your opponent's discs in a straight line between two of yours and they flip to your colour. This guide walks through the setup, a legal move, passing, the end of the game and scoring, with diagrams.

Last updated: 2026-10-09

The board and the starting position

Reversi is played on an 8×8 board of 64 squares. Four discs start in the centre, same colours on a diagonal: white on d4 and e5, black on e4 and d5. Black moves first, then the players alternate.

The yellow dots are Black's four legal first moves: d3, c4, f5 and e6. The board is symmetric, so all four are the same move rotated or mirrored. There is no "best" first move.

Placing a disc and flipping

A move must go on an empty square and must outflank at least one opposing disc: starting from the new disc, in any straight line (horizontal, vertical or diagonal), there is an unbroken run of one or more opposing discs followed by one of your own. Every outflanked disc flips.

• One move can flip discs in several directions at once.
• Only the lines through the disc you just placed count. Discs that flip do not chain and flip further discs.
• An empty square anywhere in the line breaks it. Nothing beyond the gap flips.
• If you have a legal move you must play one. You cannot choose to pass.

Below, Black plays f5. The white disc on e5 sits between f5 and the black disc on d5, so it flips.

No legal move: you pass

If it is your turn and you have no legal move, you pass and your opponent plays again. In ReversiAI the pass is automatic and announced on screen.

A player can be forced to pass several times in a row. This is common near the end of the game, and strong players aim for it deliberately: leave the opponent with nothing to play and you get two moves in a row.

When the game ends and who wins

The game ends when any of these happens:

1. All 64 squares are filled.
2. Neither player has a legal move, even if empty squares remain.
3. One player has no discs left (the other player wins immediately).

The player with more discs on the board wins; equal counts are a draw. ReversiAI compares the discs actually on the board. Some tournament rules award the remaining empty squares to the winner, which changes the margin but never the result.

Four things beginners get wrong

• Thinking you can pass. If any legal move exists you have to play one, however bad. That is exactly how strong players force you into bad moves.
• Expecting chain flips. Only discs on lines through the disc you just placed flip. Newly flipped discs never flip others.
• Counting discs in the middle of the game. The side with fewer discs is often winning. See the strategy guide.
• Waiting for a full board. The game ends as soon as neither side can move.