Reversi (Othello) is played on an 8×8 board by two players who take turns placing black and white discs. A move is legal only if it brackets at least one opponent disc in a straight line — horizontally, vertically, or diagonally. All bracketed discs are immediately flipped. Black moves first. If a player has no legal move, they pass. The game ends when neither player can move; the player with the most discs wins.
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:
| Column D | Column E |
|---|---|
| D4: White | E4: Black |
| D5: Black | E5: White |
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:
- The disc must be placed on an empty square
- The placed disc must bracket at least one opponent disc
- Bracketing occurs in a straight line (horizontal, vertical, or diagonal)
- 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
- All bracketed discs must be flipped — you cannot choose to flip only some
- Flipping happens in all applicable directions simultaneously — a single move can cause flips in 1-8 directions
- Only directly bracketed discs are flipped — the flipping does not chain (flipped discs do not cause additional flips)
- 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:
- The board is completely full (all 64 squares are occupied)
- One player has no discs remaining (all their discs have been flipped)
- No empty squares allow legal moves for either player
Determining the Winner
When the game ends:
- Count the number of black discs on the board
- Count the number of white discs on the board
- The player with more discs wins
- 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
| Misconception | Correct Rule |
|---|---|
| You can choose which discs to flip | You must flip ALL bracketed discs |
| Flipping can chain to create more flips | Flipping does not chain — only the placed disc triggers flips |
| You can skip your turn voluntarily | You can only pass when no legal move exists |
| The game only ends when the board is full | The game ends when neither player can move |
| Edge or corner squares have special rules | The same rules apply everywhere on the board |
Quick Reference Summary
- Black goes first
- Place a disc to bracket opponent discs in any straight line
- Flip all bracketed discs (mandatory, all directions)
- If no legal move exists, pass
- Game ends when neither player can move
- Most discs wins
For more guidance on strategy, see our Strategy Guide or learn about corner strategy.
Worked Examples: Legal and Illegal Moves
Understanding the rules in the abstract is easier with concrete examples. Below are common move scenarios and how to evaluate them.
Example 1: A Valid Move Flipping in One Direction
Starting position with Black to move. Black has a disc at e5, White has discs at d5 and c5, and Black has a disc at b5.
Black plays: f5
From f5, looking left along row 5: f5 → e5 (Black, stop — no opponent disc). Looking left from f5: f5 → e5 already occupied by Black. No white discs are bracketed in this direction. But if instead the line is: f5, then e5 (White), then d5 (White), then c5 (Black) — then playing at f5 would bracket e5 and d5, flipping both.
Key principle: All consecutive opponent discs between your new disc and an existing disc of yours are flipped. If there are no opponent discs in the line, or the line ends at an empty square or the board edge, no flip occurs in that direction.
Example 2: A Move Flipping in Multiple Directions
If placing a disc brackets opponent discs in more than one direction simultaneously, all bracketed discs flip. For example, placing at d3 might bracket a white disc at d4 (vertically) and bracket a white disc at e4 diagonally. Both the d4 and e4 discs flip in a single move.
The player cannot choose to flip only some; all brackets are triggered automatically and simultaneously.
Example 3: An Illegal Move
Scenario: Black attempts to place a disc on a square where no opponent discs are bracketed in any direction.
Result: The move is illegal and cannot be made. In physical play, the player must find a different square. In online play, the move is rejected automatically.
Common mistake: Placing a disc adjacent to an opponent disc without checking that a same-colour disc closes the bracket at the other end of the line. The bracket must be closed — an opponent disc in a line does not flip unless there is a friendly disc at the far end with no empty squares in between.
Example 4: Passing
Scenario: Black has checked all empty squares and none produces a legal bracket in any direction.
Result: Black must pass. White then takes their turn. If White also has no legal moves, the game ends immediately and discs are counted.
Common mistake: Voluntarily passing when a legal move exists. This is not permitted. If any legal move is available — even an undesirable one — it must be taken.
How the Game Typically Ends
In the vast majority of games, the board fills completely (all 64 squares occupied) and then the game ends. Both players count their discs and the higher count wins.
Less commonly, the game ends early because neither player has a legal move before the board is full. This can happen when one player’s discs have all been flipped (they have 0 discs remaining and therefore no disc to close a bracket) or when the remaining empty squares are all in positions that neither player can legally use.
Disc count with empty squares: If the game ends before the board is full, only the discs on the board count. Empty squares do not count for either player (in standard rules — some tournament systems add empty squares to the winner’s total, so check the specific event’s rules).
Frequently Confused Rules
“I thought the flipped discs could flip more discs”
This is one of the most common misconceptions, especially among players who know other flip-based games. Flipping does not chain in Reversi. Only the disc you place causes flips; the newly flipped discs do not trigger their own flanking checks.
“Can I place my disc on top of an existing disc?”
No. Discs can only be placed on empty squares. You cannot replace or capture an existing disc directly — you can only flip it by bracketing it through a legal move from an empty square.
“What if the board runs out of discs?”
A standard game with 64 discs will never run out if the board starts with 4 discs placed. At most, 60 additional discs are needed (one per empty square), and the full set of 64 provides exactly that. However, if using a non-standard set or if pieces have gone missing, substitute any token of the correct colour.
“Does the corner have special rules?”
No. The corner is simply a square like any other in terms of how flanking and flipping work. It is strategically powerful because it sits at the intersection of a row, column, and diagonal, and has no squares beyond it in three of the four directions — but no special rule exists for it. The same move mechanics apply.
Rules Differences: Tournament vs Casual Play
Standard Reversi rules are the same in casual and competitive play. However, competitive tournaments add procedural rules:
Time controls: Players use chess-style clocks. Typical tournament time controls give each player 25–30 minutes for all their moves. Running out of time forfeits the game.
Move recording: Players write down each move as they make it. The completed score sheet is submitted to the tournament director. See the notation guide for how to record moves.
Clock conduct: The player must place their disc before pressing the clock. Pressing the clock before completing the move is a procedural error.
Illegal move handling: If a player makes an illegal move in a tournament game, the move must be retracted and a legal move made. In some tournaments, illegal moves incur time penalties.
Pass verification: In tournament play, a player claiming they must pass must demonstrate to both players’ satisfaction that no legal move is available. The opponent may verify. If a legal move is found, it must be taken.
Draw procedures: In knockout rounds, draws may require a replay or tiebreaker by a different method depending on the tournament’s rules.
Learning to Play
With the rules fully understood, the natural next step is developing strategy. Reversi’s rules are simple but the strategy is deep — the game is famous for its steep learning curve from beginner to competent player.
Start with the beginner tips guide for practical advice that applies immediately to your first games. Then work through the complete strategy guide as you gain experience. For learning through play, Reversi Pro offers adjustable AI that gives beginners winnable opposition while gradually increasing difficulty.