Gomoku vs Renju: Rules, Differences & Which to Play

1. Introduction — Two Related But Different Games

If you have ever searched for "five in a row" online, you have almost certainly encountered two names: Gomoku and Renju. At first glance they look identical — two players, a grid board, black and white stones, and a race to connect five in an unbroken line. But look closer and you will discover that Renju is an entirely different competitive experience, shaped by a set of forbidden move rules that fundamentally change the strategy for the first player.

Understanding the distinction between Gomoku and Renju matters whether you are a casual player looking for a new challenge or a competitive player choosing which tournament circuit to enter. In this article we break down every meaningful difference — from board rules and opening protocols to strategic complexity and tournament ecosystems — so you can make an informed choice about which variant deserves your time.

If you are completely new to five-in-a-row games, we recommend reading our complete Gomoku rules guide first. If you already know the basics and want to sharpen your play, our Gomoku strategy guide covers essential patterns and tactics that apply to both Gomoku and Renju.

2. What Is Standard Gomoku?

Gomoku — known as 五目並べ (Gomoku Narabe) in Japanese, 오목 (Omok) in Korean, and 五子棋 (Wuziqi) in Chinese — is the most widely played five-in-a-row board game in the world. The rules are elegantly simple:

• Board: A 15×15 grid of intersecting lines (sometimes 19×19 in casual play or Go-board settings).
• Stones: Two players take turns — Black moves first, then White.
• Placement: On each turn, a player places one stone on any empty intersection.
• Winning: The first player to form an unbroken row of exactly five (or more) of their own stones — horizontally, vertically, or diagonally — wins immediately.
• Draw: If every intersection is filled with no winner, the game is a draw (extremely rare in practice).

Standard Gomoku — sometimes called freestyle Gomoku — imposes no restrictions on what moves either player can make. Both Black and White may freely create double threes, double fours, or lines longer than five. This simplicity makes Gomoku exceptionally easy to learn and is the primary reason for its global popularity.

However, this simplicity comes with a competitive problem. Mathematical analysis and computer solving have proven that under freestyle rules, Black can always force a win with perfect play on a 15×15 board. The first-move advantage is simply too large when no restrictions exist. This is the problem that Renju was designed to solve.

3. What Is Renju?

Renju (連珠, literally "connected pearls") is the professional, competition-grade variant of five-in-a-row. It was formally codified in Japan in 1899 when the Tokyo Renju Club (東京連珠社) established the first standardized rules. The name itself was chosen to distinguish the serious competitive game from the casual pastime of Gomoku Narabe.

Renju shares the same fundamental goal as Gomoku — be the first to connect five stones in a row on a 15×15 board. But it introduces a critical asymmetry: Black, the first player, is restricted by forbidden moves, while White plays without any restrictions at all.

The three categories of forbidden moves for Black are:

1. Double Three (三三禁手): Black may not place a stone that simultaneously creates two or more open threes.
2. Double Four (四四禁手): Black may not place a stone that simultaneously creates two or more fours (open or closed).
3. Overline (長連禁手): Black may not create a row of six or more stones. Only exactly five wins for Black.

If Black places a stone that creates a forbidden pattern, Black loses the game immediately — even if the same move would also complete five in a row. This rule creates a fascinating strategic tension: Black must attack aggressively to leverage the first-move advantage, but must do so without stumbling into a forbidden pattern. White, meanwhile, can deliberately try to force Black into positions where every natural attacking move is forbidden.

Renju's governance body is the Renju International Federation (RIF), founded in 1988, which organizes World Championship tournaments and maintains the official rules. The game has a particularly strong competitive scene in Japan, Russia, China, Estonia, and Sweden. The Renju World Championship has been held biennially since 1989, and the game has been formally recognized as a mind sport by the International Mind Sports Association.

4. Key Differences Side-by-Side

The following table summarizes every major rule and structural difference between standard Gomoku and Renju. Use this as a quick-reference comparison.

Feature	Gomoku (Freestyle)	Renju
Board Size	15×15 (sometimes 19×19)	15×15 (standard, no exceptions)
First Move	Black plays anywhere	Black must play center intersection (H8)
First-Move Advantage	Proven forced win for Black	Balanced by forbidden moves & opening protocols
Forbidden Moves	None — both players play freely	Black cannot make double threes, double fours, or overlines
Overlines (6+)	Count as a win (or draw, depending on variant)	Forbidden for Black; win for White
Opening Protocol	None (or optional Swap rule)	Mandatory (Swap, Swap2, Soosõrv, or Taraguchi)
Tournament Governing Body	No single authority; various online platforms	Renju International Federation (RIF)
Strategic Complexity	High — but solvable advantage for Black	Very high — asymmetric rules create deeper decision trees
Popularity	Worldwide casual & online play	Competitive circuits in Japan, Russia, China, Europe
World Championships	Gomoku World Championship (GWC) since 2009	Renju World Championship since 1989

As the table makes clear, the differences between Gomoku and Renju go well beyond a simple rule addition. Renju is a structurally distinct competitive game with its own theory, opening databases, and strategic traditions stretching back over 125 years.

5. Renju's Forbidden Moves Explained

The forbidden move rules are the heart of what makes Renju unique. They apply only to Black and create a constant tactical tension throughout the game. Let's examine each category in detail.

5.1 Double Three (三三 / Sansan)

A double three occurs when Black places a single stone that simultaneously creates two or more open threes (活三). An open three is a row of three stones with both ends unblocked, meaning it can be extended to an open four on the next move. When two open threes appear at once, the opponent cannot block both, making it an extremely powerful — and in Renju, forbidden — tactic for Black.

In the diagram above, if Black plays at the intersection marked ×, it would form one open three diagonally (down-right with the stones at d8, e9, and g11) and another open three horizontally (with the stones at d12 and e12). Because both are open threes created by a single move, this is a forbidden double three and Black loses immediately if played.

5.2 Double Four (四四 / Shishi)

A double four occurs when Black places a stone that simultaneously creates two or more fours. Unlike the double three rule, this applies to all types of fours — both open fours (活四, with both ends open) and closed fours (冲四, with only one end open). Even two closed fours created by a single move are forbidden for Black.

The double four rule makes Black's endgame significantly harder. In critical positions where White is building threats, Black often cannot use the most natural multi-directional attack because it would produce two fours simultaneously. Experienced Renju players on the Black side learn to plan forcing sequences that build fours one at a time, threading a tactical needle that freestyle Gomoku players never need to worry about.

5.3 Overline (長連 / Chōren)

An overline is a row of six or more consecutive stones of the same color. In freestyle Gomoku, an overline typically counts as a win (or in some rule sets, a draw). In Renju, however, the overline rule is asymmetric:

• Black: An overline is forbidden. If Black's move creates a row of six or more black stones, Black loses. Only exactly five in a row wins for Black.
• White: An overline is a valid win. White can win with five, six, seven, or any number of consecutive stones.

The overline restriction adds yet another layer of complexity to Black's play. In the endgame, Black must carefully count the length of every potential line before placing a stone. A careless extension that turns five into six is an instant loss — and White can exploit this by building long partial lines that threaten to trap Black into an overline.

6. Opening Protocols in Renju

Forbidden moves alone are not sufficient to fully balance Renju at the highest levels of play. Over decades of competitive experience, the Renju community developed opening protocols — structured procedures for the first several moves — to further equalize the game. These protocols ensure that neither player can rely on memorized forced-win sequences from the very start.

Swap Rule

The original balancing mechanism. Black places the first three stones (one black, one white, one black), then White may choose to swap — taking control of the Black stones and giving their White stones to the opponent. The idea is that Black must create a fair, balanced opening, because placing an overly aggressive opening means White will swap and take the advantage for themselves.

Swap2 Rule

An evolution of the Swap rule, widely used in Gomoku tournaments and many Renju events. After Black places three stones (two black, one white), White has three choices:

1. Accept — play as White from the current position.
2. Swap — take control of the Black position.
3. Place two more stones (one white, one black) and let the original Black player choose which color to play.

Swap2 gives significantly more flexibility than the basic Swap and is considered the fairest opening protocol for online and casual tournament play. It is the protocol we use here on Gomoku Five's online platform.

Soosõrv Rule

Named after the Estonian town where it was devised, Soosõrv is the opening protocol currently used in official RIF World Championship tournaments. It is the most complex of the three main protocols:

1. The first player places three stones (two black, one white) from the 26 recognized standard opening patterns.
2. The second player chooses color (Black or White).
3. The player now holding White places the 4th stone.
4. The player holding Black declares how many possible "fifth moves" will be offered (at least one).
5. Black places that many candidate 5th-move stones on the board.
6. White removes all but one of the candidate stones, and play continues normally from that position.

Soosõrv ensures that even the most well-studied openings remain balanced, because the offering-and-removal mechanism gives both players agency over the resulting position. It largely eliminates the possibility of memorized forced-win sequences surviving past the opening phase.

7. Which Should You Play?

There is no single correct answer — the best variant depends on your goals, experience level, and what you want from the game. Here are our recommendations for different player profiles:

Choose Gomoku (Freestyle) If You…

• Are a beginner learning five-in-a-row — Gomoku's symmetric, restriction-free rules let you focus entirely on learning patterns like open threes, open fours, and double threats without worrying about forbidden moves.
• Play casually with friends or family — the rules require zero explanation beyond "first to connect five wins."
• Want to play online quickly — most online platforms default to freestyle or Swap2 Gomoku, making it easy to find opponents at any time.
• Enjoy symmetric puzzles — the mathematical solvability of Gomoku is itself an interesting study for puzzle enthusiasts.

Choose Renju If You…

• Want a deeply balanced competitive game — Renju's forbidden moves eliminate Black's forced-win advantage, making every game genuinely contestable.
• Enjoy asymmetric strategy — playing Black in Renju feels fundamentally different from playing White, creating two distinct strategic experiences in one game.
• Aspire to competitive tournament play — the Renju tournament circuit is well-established with a clear path from local to World Championship level.
• Have mastered Gomoku and want more depth — the forbidden-move layer adds a dimension of tactical calculation that never exists in freestyle play.

8. Other Five-in-a-Row Variants

Gomoku and Renju are the two most prominent five-in-a-row variants, but the family extends further. Here are four other notable variants you may encounter:

9. Conclusion

Gomoku and Renju are siblings, not twins. They share the same DNA — a square grid, alternating black and white stones, and the objective of five in a row — but the addition of forbidden moves in Renju creates a profoundly different competitive game. Gomoku offers accessible, symmetric play that anyone can enjoy within minutes of learning the rules. Renju offers the deepest possible five-in-a-row experience, with over a century of competitive tradition, formal opening theory, and strategic ideas found nowhere else in the family of connection games.

The good news is that you don't have to choose only one. The skills you develop in Gomoku — pattern recognition, threat calculation, positional judgment — transfer directly to Renju. And the discipline required by Renju's forbidden moves will make your Gomoku play sharper and more precise. Learn both, play both, and you will gain a richer appreciation for one of the world's oldest and most elegant strategy game families.

Whichever variant you choose, the best way to improve is to play. Every game teaches you something new — a pattern you hadn't seen, a trap you fell into, a combination you discovered. So close this article, open a board, and start placing stones.

Recommended Next Reading

• Complete Gomoku Rules Guide — Master every rule and variation of five-in-a-row.
• Gomoku Strategy Guide — Learn winning patterns, double threats, and advanced tactics.
• Gomoku Openings Guide — Study the 26 standard opening patterns used in competitive play.
• Play Gomoku Online — Start playing right now against real opponents for free.