The passing rule

Passing is the rule new players most often get wrong, usually because they assume it works like passing in a card game. It does not. In Reversi a pass is something the board does to you, not something you decide.

The rule

1. On your turn, look for a square that would flip at least one disc.
2. If one exists, you must play a move. Any of them, but one of them.
3. If none exists, you pass. Your opponent moves again.
4. Nothing else changes. No penalty, no lost disc, and you take your next turn as normal as soon as you have a legal square.

What a forced pass looks like

Here is a position ten moves into a real game. Black is ahead 10 discs to 4, and has 0 legal moves anywhere on the board. Every empty square either flips nothing or is not touching a white disc at all. So Black passes, and White plays again with 2 options: c3 and d6.

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Look at the shape rather than the count. Black's discs sit in a tight block in the middle, hemmed in by white discs on the outside. Everything Black owns is surrounded by other black discs, and that is exactly the position from which you cannot move. Having lots of discs and no room is one of the worst places to be in this game. Mobility is the idea behind that.

How early can it happen?

Very early. The soonest a pass is possible is after 8 moves, which we found by playing out every legal game from the start and checking. In the position below, Black has 0 legal moves and White plays again with 2: e3 and f6.

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In practice most games have one or two passes somewhere in the middle, and some have none at all. Games with lots of passes usually mean one player has taken a strong grip on the shape of the board.

Moving twice, or more

When your opponent passes, you move again. If they still have nothing after that, you move a third time. There is no limit, and it is not cheating. A run of three or four moves in a row late in the game usually means the opponent is about to lose badly.

If you are playing the computer here and it seems to have moved twice, that is what happened: your turn was skipped because you had no legal square. The board tells you when it happens rather than leaving you to guess.

Writing a pass down

Standard Othello notation does not have a symbol for a pass. A game is a run of square names, and the same player simply appears twice in a row. Any correct replay will work out that a pass happened, because the rules make it the only possibility. How notation works.

Passing as a weapon

Forcing your opponent to pass is one of the strongest things you can do, because you get a free move. Two free moves in a row late in the game can win you a corner and the discs anchored to it.

The way to make it happen is to keep your own discs few and spread out, and to leave your opponent with a solid block. That is the opposite of what feels right, and it is most of what separates a beginner from a decent player. The strategy guide and how to win both start here.

Watch it happen

Play a game on the board on this site and keep an eye on how many legal squares you have compared with your opponent. When that number drops to one or two, a pass is usually a move or two away. The computer opponent at Intermediate and above will actively try to take your moves away, which makes the effect easy to see.

Related: legal moves, when a game ends and the complete rules.