Official Reversi (Othello) Rules: Complete Reference Guide

Official Rules of Reversi (Othello)

This guide serves as a complete reference for the official rules of Reversi, also known as Othello. Whether you need to settle a dispute, prepare for tournament play, or simply understand every detail of the game, this guide has you covered.

Equipment

• Board: An 8×8 grid (64 squares), traditionally colored green
• Discs: 64 identical discs, each with a dark (black) side and a light (white) side
• Players: Two — one designated Black, the other White

Starting Position

The game starts with four discs placed in the center four squares of the board:

This creates a diagonal pattern with alternating colors. The arrangement is fixed — the starting position is always the same.

Black moves first in the standard (Othello) rules.

Legal Moves

A legal move must satisfy ALL of the following conditions:

1. The disc must be placed on an empty square
2. The placed disc must bracket at least one opponent disc
3. Bracketing occurs in a straight line (horizontal, vertical, or diagonal)
4. The line must contain one or more consecutive opponent discs between the newly placed disc and an existing disc of the player’s own color

Bracketing Explained

When you place a disc, imagine lines extending in all eight directions from that square:

• Up, Down, Left, Right
• Upper-left, Upper-right, Lower-left, Lower-right

In each direction, if the line passes through one or more consecutive opponent discs and then reaches one of your own discs (with no empty squares in between), those opponent discs are bracketed and must be flipped.

Flipping Rules

1. All bracketed discs must be flipped — you cannot choose to flip only some
2. Flipping happens in all applicable directions simultaneously — a single move can cause flips in 1-8 directions
3. Only directly bracketed discs are flipped — the flipping does not chain (flipped discs do not cause additional flips)
4. Flipping is mandatory — if your move brackets discs, they must all be flipped

Maximum Flips

The theoretical maximum number of discs that can be flipped in a single move is 18. This is extremely rare but possible in specific board configurations.

Passing

• If you have no legal moves available, you must pass your turn
• Your opponent then takes their turn
• If your opponent also has no legal moves, the game ends
• You cannot voluntarily pass when you have a legal move available
• Passing is automatic in online play and forced in tournament play

Game End Conditions

The game ends when neither player can make a legal move. This most commonly occurs when:

1. The board is completely full (all 64 squares are occupied)
2. One player has no discs remaining (all their discs have been flipped)
3. No empty squares allow legal moves for either player

Determining the Winner

When the game ends:

1. Count the number of black discs on the board
2. Count the number of white discs on the board
3. The player with more discs wins
4. If both players have exactly 32 discs, the game is a draw

Tournament Scoring

In competitive play, the margin of victory often matters:

• Score format: Winner’s count – Loser’s count (e.g., 40–24)
• Empty squares: In some tournament systems, remaining empty squares are added to the winner’s count
• A perfect game (64–0) means one player captured every square

Special Rule Clarifications

Multiple Direction Flips

A single move can flip discs in multiple directions. You must identify and flip ALL bracketed discs in every direction from your placed disc.

Example: If placing a disc at position C3 brackets white discs along the row (C4, C5) AND along a diagonal (D4, E5), all of those discs are flipped in that single move.

Edge and Corner Moves

The same bracketing rules apply at edges and corners. There are no special rules for these positions — they simply have fewer possible directions for bracketing.

No Chain Reactions

Flipping is a single action. When discs are flipped, they do not cause additional flips. Only the original placement triggers the flipping process.

Disc Supply

In the physical game, if all 64 discs are in use before the board is full, players use a substitute (such as a coin or piece of paper) to represent additional discs. In online play, this is handled automatically.

Tournament-Specific Rules

Competitive Reversi (Othello) tournaments follow additional rules:

• Time control: Each player has a set amount of time for all their moves (typically 25-30 minutes per player)
• Recording: Players may be required to record their moves
• Black assignment: Tournament pairings determine who plays Black (first mover) and White
• Draw handling: In elimination rounds, draws may require tiebreaker games
• Clock procedure: A player must make their move before pressing the clock
• Spectators: No assistance from spectators is permitted

Common Misunderstandings

Quick Reference Summary

1. Black goes first
2. Place a disc to bracket opponent discs in any straight line
3. Flip all bracketed discs (mandatory, all directions)
4. If no legal move exists, pass
5. Game ends when neither player can move
6. Most discs wins

For more guidance on strategy, see our Strategy Guide or learn about corner strategy.