Gomoku vs Renju: Rules, Forbidden Moves and Key Differences
Gomoku vs Renju in one sentence: both are five-in-a-row games on a 15×15 board, but Renju forbids the first player (Black) from making double threes, double fours and overlines, and uses a formal opening procedure. Those rules exist to offset the first player's advantage. Freestyle Gomoku has no such restrictions.
This page explains each difference objectively. For the basic rules both games share, start with the Gomoku rules.
Summary table
| Freestyle Gomoku | Standard Gomoku | Renju | |
|---|---|---|---|
| Board | 15×15 (often 19×19 casually) | 15×15 | 15×15 |
| First move | Black | Black | Black |
| Black wins with | Five or more | Exactly five | Exactly five |
| White wins with | Five or more | Exactly five | Five or more |
| Restrictions | None | None | Black may not make a double three, double four or overline |
| Opening | Free in casual play | Usually swap2 in competition | Formal opening rule |
All diagrams below use X for Black and O for White.
Gomoku rules
Gomoku keeps things symmetrical. Both players follow the same rules: alternate stones, and the first to five wins. In freestyle Gomoku five or more wins; in standard Gomoku only exactly five counts, for both players. Competitive Gomoku addresses the first-move advantage through the opening — most often swap2, in which the first three stones are placed before either player commits to a colour — rather than through rules that apply during the game.
Renju rules
Renju keeps the same board and objective but treats the two players differently:
- Black moves first and must not make certain moves (below).
- Black wins with exactly five in a row.
- White has no restrictions and wins with five or more in a row.
- If Black makes a forbidden move, White wins. The one exception: if Black's move makes five in a row at the same time, the five counts and Black wins.
- The game starts with an opening rule that controls how the first stones are placed.
Renju is governed internationally by the Renju International Federation (RIF), founded in 1988.
The first-player advantage
The restrictions are a response to a real imbalance. Computer analysis by Victor Allis in 1994 showed that freestyle Gomoku on a 15×15 board is a first-player win with perfect play. Analysis published in 2001 showed the same for Renju when it is played without an opening rule, despite Black's restrictions. That is one reason Renju pairs its restrictions with opening rules: the restrictions alone do not remove the first player's edge.
None of this means Black wins every human game. Perfect play is far beyond human reach. But between strong players, an unrestricted first move is a measurable edge.
Forbidden moves
Black may not place a stone that creates any of the following.
Double three
A move that creates two open threes at once.
The precise definition matters in Renju: a three only counts if it could become a straight four — four in a row with both ends open — without that four itself requiring a forbidden move. The official rules spell out these cases in detail.
Double four
A move that creates two fours at once.
Overline
Six or more stones in a row.
For White, the same six in a row is a win.
What Black can still do
Black is allowed to make a four-three — a four and an open three with one move — and that is Black's main way to win in Renju. Black can also win by a sequence of fours, as long as no move in it creates a forbidden shape. The Gomoku tactics guide explains how four-threes work.
How forbidden moves change play
The restrictions remove Black's simplest winning patterns, the double three and the double four. They also give White a weapon: White can sometimes defend by forcing Black into a position where the only way to block is a forbidden point. A Black player has to check every move for forbidden shapes, and a White player looks for chances to create them.
None of these considerations exist in freestyle Gomoku, where every empty point is a legal move for both players.
Overlines compared
| Rule set | Six in a row for Black | Six in a row for White |
|---|---|---|
| Freestyle Gomoku | Wins | Wins |
| Standard Gomoku | Does not win | Does not win |
| Renju | Forbidden — White wins | Wins |
| 5Row | Wins | Wins |
Opening systems
Opening rules decide how the first few stones reach the board, and often let players swap colours along the way, so that neither side starts with a known advantage.
- Gomoku competitions commonly use swap2: one player places three stones (two black, one white), and the other may take White, swap to Black, or place two more stones and pass the choice back.
- Renju has used several opening rules over the years, including the RIF rule, Yamaguchi, Taraguchi and Soosõrv rules. They typically combine a set of standard opening positions, opportunities to swap colours, and a stage where Black proposes several possible fifth moves and White chooses which one is played. The RIF adopted the Soosõrv-8 rule for its world championships from 2017.
For casual play none of this is necessary, but it explains why published Renju opening theory looks so different from casual Gomoku openings. Our Gomoku opening strategies cover openings for games without an opening rule.
Why Renju adds restrictions
Renju's rules aim for a game that remains balanced when both players are strong. Freestyle Gomoku is easier to learn and fair enough between casual players, but at expert level the first player's edge becomes a problem. Renju accepts more complicated rules in exchange for closer games at the top.
That is a trade-off, not a ranking. Renju is not simply "harder Gomoku": it asks different things of each side, and the forbidden-move rules add a layer of calculation that freestyle players never need.
Which rules does 5Row use?
5Row does not use Renju rules:
- There are no forbidden moves for either player; double threes, double fours and overlines are all legal.
- Five or more in a row wins for both players.
- There is no opening rule — X simply moves first.
- The Vietnamese two-end rule is on by default: an exact five blocked at both ends does not win, and six or more always wins.
The two-end rule also makes life easier for the defender, but it applies to both players equally rather than restricting the first player. You can play a game with it on, or switch it off in practice. Our Caro vs Gomoku comparison explains where it comes from and how it changes play.
FAQ
Should I learn Gomoku or Renju first?
Gomoku. Every Gomoku idea — threes, fours, double threats — carries over to Renju, and you can add the forbidden-move rules later. The Gomoku strategy guide is a good place to start.
Can White make a double three in Renju?
Yes. White has no restrictions in Renju and can use double threes, double fours and overlines.
What happens if Black makes a forbidden move?
White wins — unless the same move also makes five in a row for Black, in which case the five counts and Black wins.
Is the board the same size?
Yes. Both competitive Gomoku and Renju use 15×15. Casual Gomoku is also often played on 19×19, and 5Row uses a 19×15 board.
Can I play Renju on 5Row?
Not at the moment. 5Row plays freestyle-based Gomoku with an optional two-end rule. You can still practise four-three combinations, which are legal for both players in every rule set.