Omok, the Other Game on a Go Board
Omok (오목, "five eyes") is named for exactly what it takes to win: five of your own stones in a row, horizontally, vertically, or diagonally. As far as rules go, it's about as simple as board games get. What's less obvious is that Omok didn't start as its own invention. It grew out of a side game played on a spare Go board with Go stones, something people played while waiting for a Go match, or that children learned before picking up Go itself.
Origins: From China to Japan
Games built around "connect five in a row" go back far enough that no single origin point is settled history. Records point to a similar game called Wuziqi (五子棋) in China. As the game traveled to Japan alongside Go, it took the name "Gomoku Narabe" (五目並べ, "lining up five"), and that Japanese name is exactly where the English word Gomoku comes from.
In Korea the game settled under its own Hanja name, Omok (五目). Because all it needs is a Go board, it naturally spread through the same rooms and Go clubs where Go itself was played.
Why the First Player Wins: the Birth of Renju
Omok's simplicity comes with a catch: played with no restrictions at all, the first player (Black) has a decisive advantage. It's been shown that with precise enough play, Black can force a win regardless of how well White defends, which threatens to turn unrestricted Omok into a game where moving first simply means winning.
To fix that imbalance, Japan developed the Renju (連珠) ruleset. The name "Renju" was coined in 1899 by the Japanese journalist Ruikō Kuroiwa. [Source: Wikipedia] Renju places a few restrictions on Black only.
- No double-three (33): Black may not play a move that creates two open threes (three in a row, open on both ends) at once.
- No double-four (44): Black may not play a move that creates two fours at once, either.
- Overline doesn't count: If Black lines up six or more in a row, it does not count as a win. Only exactly five does.
White has none of these restrictions, and six-or-more in a row still counts as a win for White. Handicapping only the first player like this is what turns Omok into a genuinely balanced contest, and it's why Renju became the official ruleset for international competition. The Renju International Federation (RIF), founded in 1988, has held a World Championship every two years since 1989. [Source: Wikipedia]
What Ruleset Does Omokboard Use?
Renju's forbidden moves are great for competition, but confusing for a beginner ("why can't I play there?"). That's why Omokboard, like most casual Omok games, uses free-style rules: either side can play anywhere, and five in a row wins outright, no exceptions.
Worth keeping in mind, though: free-style makes the first-move edge real. If you're Black, claim the center early and build open threes aggressively; if you're White, your job is blocking the opponent's open threes and fours the moment they appear. For concrete attack-and-defense patterns, see the Omok strategy guide.
Omok in Korea: a National Pastime
Because it needs nothing more than a Go board (or a grid drawn on paper), Omok has long been a low-effort way to pass time in Korea: during a school break, at an internet café, anywhere. The rules take under a minute to explain, yet the game rewards reading your opponent's next move well ahead of time, which is exactly why it's stayed popular across every age group.
Play Omok Online
Omokboard lets you play Omok with no install and no sign-up. Practice solo against three AI difficulty levels, play 2-player on one screen, or create a room code to play in real time with a friend anywhere. See the online play guide for how room codes work.
FAQ
- Are Omok and Gomoku the same game? Yes, it's the same game under different names. Gomoku is the English form of the Japanese name; Omok is the Korean Hanja name.
- What's the difference between Renju and Omok? Renju is the competitive ruleset that bans double-threes, double-fours, and overlines for Black to prevent a forced first-move win. Ordinary (free-style) Omok has none of those restrictions.
- Does Omokboard use Renju rules? No. Omokboard uses free-style rules so beginners can play without hitting confusing forbidden-move restrictions.
- Is going first really an advantage? Yes, in free-style rules Black (first player) has the edge. In 2-player mode on Omokboard, it's worth alternating who goes first each game.