Gomoku threats and forks

Version 1.0 · Updated 31 July 2026. A threat is valuable because it limits the opponent's legal useful replies.

Open three

Three connected stones with useful empty space at both ends can grow into an open four. Example on row 8: F8, G8, H8 with E8 and I8 empty.

Open four

Four connected stones with two empty endpoints has two immediate winning points. In Freestyle, stones at F8–I8 threaten E8 and J8.

Closed four

A closed four has only one winning endpoint because the other end is blocked by the edge or an opposing stone. It still requires an immediate defence.

Double threat

A fork creates two independent winning routes with one move. Blocking one route leaves the other. Fivefold Gomoku's hint first marks the opponent's strongest danger, then the candidate response.