2000-06-08 last update, 1996-09-23 first day, Robert Jasiek

Super Ko

A board play may not recreate a position.


After the primitive ko rule super ko is the simplest of all rule sets, that restrict moves to ensure a finite go game end. Super ko is only one rule, which prohibits repetition of whole board position. Strictly speaking, super ko is no ko rule because no ko is defined, but a restriction rule. The above rule is the standard variant of super ko, called positional super ko. Other variants of a restriction rule exist. They are said to belong to the repetition class of ko rule sets. Examples are available.

Major Variants

primitive ko: A move may not recreate a position.

positional super ko: A board play may not recreate a position.

situational super ko: A board play may not recreate a position previously left by the player.

natural situational super ko: A player may not use a board play to recreate a position if he has used one to create it.

fixed ko: A board play may not recreate a pair of positions.


The primitive ko rule is only of game theoretical interest: The first player without a legal move loses. Hereby the only available move type is board play; primitive rules do not use pass plays.

A move is either a pass play or a board play. A pass play gives the other player the right to move. A position is a whole board together with its configuration of stones. Recreation refers to any prior position during a game and can never occur, because each of the rules prohibits it. A player leaves a position by finishing the performance of one of his moves. I.e. super ko refers to positions after completion of moves.

The actual difference of positional super ko and situational super ko as to occuring positions is rather small. Very few distinguishing examples are known. With its longer text situational super ko allows slightly more variation. With positional respectively situational super ko repetition analysis refers to a position respectively a position together with the right to move.

The natural situational super ko rule treats causes and consequences as to prohibition the same way: Both can only arise due to board plays. Thus natural situational super ko is conceptionally clearer than situational super ko that also allows pass plays to cause situational prohibitions. In practice, natural situational super ko and situational super ko have almost always the same outcome, although natural situational super ko sometimes allows unfamiliar move sequences.

Fixed ko is a multiple repetition rule: the position before and the position after a board play are considered together and in order for prohibition. So not recreation of just one position is prohibited but recycling. As a practical result, no ko fight at all occurs. Any ko is a so called disturbing ko. Hence strategy and tactics, incl. life and death, are severely altered. The rule is of great theoretical importance, however, it could also be misused for simplified go.


Positional Super Ko

Situational Super Ko

Natural Situational Super Ko



A super ko rule is neither used to justify any special position nor to maintain exceptionally void games. Traditionalists may regard this as a disadvantage. However, the only logical flaw is the possibility of move-sequences of exponential length depending on the number of board points. This is generally known as the problem for players to recognize repetition with many kos on the board. The Basic Ko Rules are a possible alternative by allowing linear length in all practical cases.


To Ikeda Toshio for promoting the simplest useful ko rule. To Matti Siivola for proposing the terms "positional" and "situational". To all having provided historical information. To all promoting super ko.