Reversi Rules - How to Play
Reversi is an 8×8 game of placement and reversal. Every legal disc must trap at least one opposing disc and turn the whole trapped line to your color.
The board and opening position
Reversi uses an 8×8 board with 64 squares. The game begins with four discs in the center: White on d4 and e5, Black on e4 and d5. Black moves first. Squares outside that opening are empty, and a disc stays on its square once placed; only its color can change through a flip.
Players alternate colors for as long as legal moves exist. The board labels columns a through h and rows 1 through 8, with a1 at the top left in this implementation. Coordinates help describe a move, but legality always depends on the discs surrounding the empty square, not on a chosen opening book or a special named square.
What makes a move legal
You may place a disc only on an empty square that brackets one or more opposing discs. Starting from your new disc, look in any horizontal, vertical, or diagonal direction. There must be a continuous run of opponent discs followed by one of your own discs, with no empty square between them. Every opposing disc in that completed line flips to your color.
A move may flip in several directions at once. For example, a disc can complete a horizontal line and a diagonal line simultaneously, flipping both runs. A nearby opponent disc alone is not enough: without one of your discs beyond it in the same straight direction, that line does not make the placement legal. You cannot voluntarily place a disc that flips nothing.
Flipping the bracketed discs
After you place a legal disc, flip every trapped opposing disc in every qualifying direction. A line stops at the first disc of your own color, so only the contiguous opposing discs between that endpoint and your new disc change color. Empty squares stop a line, and discs beyond your own endpoint are unaffected. The placed disc and all flips belong to your color immediately before the next player considers a move.
This means the visible score can change sharply. A move that flips six discs adds one new disc and converts six more, changing the difference by thirteen relative to the opponent’s count. That swing is normal, but it does not alter the turn order: after a legal move, the other color is considered next unless that color has no legal square.
Passing when no move exists
If the player whose turn it is has no legal move anywhere on the board, that player must pass. Passing is automatic here; you do not choose it to preserve a favorable position. If the opponent has a legal move, the same player who just moved takes another turn after the pass. A pass therefore does not mean the game has ended, and it is worth checking the full board before assuming a turn is over.
Only the absence of every possible bracketed placement causes a pass. Having a move that flips few discs still requires a move. The game does not use a voluntary-pass rule, a draw offer, or a separate repetition rule. Continue applying the normal placement and flip test after each pass.
The end and scoring
The game ends when neither Black nor White has a legal move. This often happens when the board is full, but it can happen with empty squares remaining if no empty square brackets a line for either side. Count the discs on the finished board. The player with more black or white discs, according to their color, wins. Equal counts produce a draw.
There is no territory score, bonus for corners, or compensation for moving second in this version. Corners matter strategically because they are hard to flip, not because they score extra points. The final result is simply the number of discs of each color after the last required pass or last legal placement.
Reversi rules FAQ
- Can I place a disc next to an opponent without flipping it?
- No. Every placement must bracket and flip at least one opposing disc in a straight line.
- Can one move flip discs in more than one direction?
- Yes. Flip every continuous bracketed line created horizontally, vertically, and diagonally by the same placement.
- May I pass when I have a legal move?
- No. A pass happens only when there are no legal moves for the player to move.
- Does a full board always end the game?
- Yes, because no empty square remains. The game can also end earlier when both players lack a legal move.
- How is a tied game decided?
- If Black and White have the same final number of discs, the game is a draw.
Practice the rules on the board
Use the legal-move highlights to trace each bracket before you play, then compare the board after every flip.