Play Gomoku Online — Renju Rules, Forbidden-Move Referee
Five in a row on a 15×15 board, with full tournament Renju balance: double-three, double-four and overline detection for Black, VCF tactics, smart AI and a global Elo ladder.
✨ Why play here
⚖️ Real tournament balance
Black's double-threes, double-fours and overlines are detected live — the referee rules exactly as a Renju arbiter would.
🧮 Threat-aware AI
The engine reads open threes, broken fours and full VCF chains, so wins feel earned rather than gifted.
🏆 Ranked and casual play
Jump into rated ladder games or friendly rooms; every game is replayable stone by stone.
📱 Precise on touch
A magnified placement cursor and confirm-tap option eliminate misplaced stones on phones.
📖 How to play (and why Black is handicapped)
Players alternate placing stones on a 15×15 grid of intersections. The first to make an unbroken line of exactly five — horizontally, vertically or diagonally — wins.
Under free rules the first player wins with perfect play, so tournament Renju restores balance by forbidding Black from playing:
- Double-three (三三) — one stone creating two open threes at once;
- Double-four (四四) — one stone creating two fours at once;
- Overline (长连) — a line of six or more stones.
White has no restrictions — and at higher levels White's sharpest weapon is steering Black into positions where every winning reply is forbidden.
The vocabulary of threats
An open three must be answered or it becomes an open four, which is unstoppable. A four demands an immediate block. Stack these ideas and you get the VCF — an unbroken sequence of fours that ends in a double threat. Most decisive games at every level are settled by someone spotting, or missing, a VCF three moves earlier.
❓ Frequently Asked Questions
What is the difference between Gomoku and Renju?
Free-style Gomoku is simply five in a row on any move. Renju is the tournament version: because the first player wins with perfect play under free rules, Black (who moves first) is banned from making a double-three, a double-four, or an overline of six or more stones. This site implements full Renju forbidden-move refereeing.
What happens if Black plays a forbidden move?
The referee engine flags it and Black loses immediately — exactly as in tournament Renju. White has no forbidden moves and can even win by deliberately forcing Black into a position where every strong reply is forbidden.
What is a VCF?
VCF — Victory by Continuous Fours — is a forced win where the attacker plays an unbroken chain of four-in-a-row threats. Each four must be answered, and the chain ends in an unstoppable double threat. Reading VCF sequences is the core calculation skill of competitive Gomoku.
Can I play against the AI or only against people?
Both. The AI understands forbidden moves and VCF threats and comes in several strengths, and live PvP with Elo ladder ranking is always available. Both are free.