Byo-yomi

Byo-yomi is the overtime phase of a Go game. After using the main time, a player must continue making moves under a specified countdown or period-based time limit. It allows the game to continue while preventing indefinite play.

Depending on the ruleset, a player may receive one or more fixed periods, or a fixed number of seconds in which to play a set number of moves. The applicable period or countdown may reset after the required moves are completed. Some systems instead use a continuous Canadian-style overtime countdown. Exceeding the applicable limit loses the game on time.

Byo-yomi specifically means overtime after the main time; it does not refer to the entire game clock or to fast time controls such as a rapid game.