Official Othello rules

If you need an authority to point at, point at the World Othello Federation. This page summarises what they publish, explains the parts that only matter in tournaments, and links straight to the source so you can check it yourself.

Where the official rules live

The World Othello Federation is the international body for the game. It runs the World Othello Championship and publishes the playing rules on its site, in English and Dutch, with translations into several other languages.

• Official rules for the game Othello, the playing rules in English.
• World Othello Championship rules, the tournament regulations, published as a PDF.
• worldothello.org, the federation itself.

The playing rules, in brief

These are the rules as the federation states them, summarised. The wording is ours; the substance is theirs.

1. Black always moves first. No toss, no choice. More on this.
2. A move must outflank and flip at least one opposing disc. Outflanking means placing a disc so that a row of your opponent's discs is bordered at each end by a disc of your colour.
3. A single move can outflank in several directions at once. Rows run across, down and diagonally, and every direction that closes flips.
4. You may not skip over your own disc to outflank an opposing one. The run has to be unbroken.
5. Discs are only outflanked as a direct result of a move. A disc that flips does not go on to trap more discs behind it.
6. All outflanked discs must be flipped, even when flipping fewer would suit you better.
7. A placed disc never moves again. It stays on its square for the rest of the game and only changes face.
8. If you cannot outflank, your turn is forfeited and your opponent moves again. If a move is available to you, you may not forfeit your turn. The passing rule.
9. If you run out of discs while you still have a legal move, your opponent must give you discs to use.
10. When neither player can move, the game is over. Count the discs; the majority wins. The federation notes directly that a game can end before all 64 squares are filled.

Those are the same rules the board on this site plays by, and the same ones set out in full on the rules page.

The starting position

Black places two black discs and White places two white discs on the four centre squares, arranged so the colours sit diagonally opposite. Black then has four legal opening moves: d3, c4, f5, e6.

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What tournaments add

The playing rules do not change in a tournament. What gets added is procedure, taken here from the World Othello Championship regulations.

Clocks

Each player has a fixed amount of time for all of their moves in a game. At the World Othello Championship that is 30 minutes per player in the early rounds, 35 in the semi-finals and 40 in the final. Running out of time loses the game whatever the board looks like, and a game lost that way is recorded as a 64-0 defeat.

Scoring and empty squares

The winner is the player with more discs when neither side can move. The recorded score counts the discs of each colour and gives any empty squares to the winner, so the two numbers always add up to 64.

Here is a real game that stopped with 1 square still empty. On the board it is White 39 to Black 24. Recorded for a tournament it becomes White 40 to Black 24.

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A draw is always recorded as 32-32, whatever the board looked like. Resigning, or being unable to finish a game for any reason, is recorded as 64-0 in the opponent's favour. Scoring worked through.

Illegal moves

When a mistake is spotted, an official stops the clock, corrects the position and restarts play. Only the most recent move can be challenged. Once a player has answered it, they have accepted the position and it stands.

Recording the game

A table judge keeps a transcript where one is assigned. Where none is, both players are responsible for keeping one. If a dispute comes up and only one player has a transcript that matches the board, that transcript settles it. Record keeping must never get in the way of the players' concentration. How the notation works.

What the official rules do not cover

• Variants. Anti-Othello, larger boards and the free-placement opening are outside the official rules. Variants.
• Old Reversi. The Victorian game had its own conventions, including letting players choose the opening layout. History.
• Strategy. Nothing in the rules says anything about corners, mobility or parity. Strategy.

A note on the name

Othello is a registered trademark of MegaHouse Corporation and Othello, Co. This site is not affiliated with or endorsed by the trademark holders. "Reversi" is the public-domain name for the same game.

In practice this means that the rules are free to describe and play, while the name Othello belongs to somebody. The game is identical under either name. The two names compared.

Play by these rules

The board on this site follows the federation's playing rules exactly, including the pass and the game ending when neither player can move. Every diagram on this page was generated by that same code rather than drawn by hand, so what you see here is what the board will do. Play a game and check.

Related: the complete rules, scoring and a printable rules sheet.