Most beginners never think about it until it happens: you have a row of marks with a single gap in it, you drop a mark into the gap, and suddenly you have six in a row instead of five. Does that win?
The answer depends on which rule set you are playing. This short guide explains the term overline, how the main gomoku families treat it, and when the question actually matters in a real game.
What is an overline?
An overline is an unbroken line of six or more marks of the same player. It usually appears by accident, when a player fills a gap between two shorter lines, or deliberately, when a player has more than enough marks in a row and simply adds another.
The main rule families
Freestyle gomoku
Five or more wins. An overline counts as a win just like an exact five. This is the rule used in freestyle mode on the home board, and it is the simplest possible answer: if you have at least five in a row, you win.
Standard gomoku
In what is often called standard gomoku, only exactly five wins. A line of six or more does not count. The idea is to make the winning condition precise and slightly harder to reach, which trims a little of the first player's advantage.
Renju
Renju is the professional variant with special restrictions on the first player (black, in renju). In renju, the first player may not make an overline — doing so is a forbidden move — while the second player may win with an overline. Renju also forbids the first player certain double threats. These asymmetric rules exist to balance a game in which the first player has a large theoretical advantage.
Vietnamese caro
Everyday Vietnamese caro focuses on a different question — whether the five is blocked at both ends — rather than on overlines. House rules vary, and players on paper rarely argue about sixes because they almost never happen in practice. If you are playing a serious game with friends, simply agree beforehand whether six counts.
Why would anyone forbid six in a row?
It seems strange at first: if five wins, why would six — which contains a five — not win? The logic is about precision and balance.
In unrestricted play, the first player can often force a win with enough accuracy. Every restriction that makes the winning condition stricter gives the defender a little more room. Forbidding overlines means some attacking shapes that would otherwise win do not, because completing them produces six rather than five. Renju pushes this further by restricting only the first player, which is where the advantage lies.
When does it actually matter?
Less often than you might think. In most games the winning line forms as a clean five at the edge of an attack. Overlines become relevant mainly in two situations:
1. Filling a gap between two lines. If you have two groups on the same line, like X X X _ X X, filling the gap makes six. Under exactly-five rules that is not a win, so the gap is not a threat at all — a detail that can matter a great deal to the defender.
2. Long attacks along one line. In a long fight, one row may collect many marks. Late in the game you may have a choice between two points on that line, one making exactly five and one making six. Under exactly-five rules only one of them wins.
In this diagram, under freestyle X simply plays h8 and wins. Under exactly-five rules h8 is useless, and X would have to look for a genuine five elsewhere — for example by extending from the left end if c8 is open, which would make exactly five from c8 to g8 only if h8 stays empty.
A habit worth building
Whatever rule you play, it helps to count exactly when a line gets long. Strong players always know how many marks are on a line and where the ends are. This matters for overlines, and it matters even more under the blocked-ends rule, where the ends decide whether a five wins at all.
Overlines from the defender's point of view
The overline question is not only about the attacker. Under exactly-five rules, a defender sometimes has a quiet resource: they can leave a gap alone because filling it would only make six. That frees a move for something more useful.
Consider X X X _ X X on a single line. In freestyle this is a deadly threat — one move in the gap wins — so the defender must block the gap immediately. Under exactly-five rules the gap does nothing for X, and the defender can ignore it and spend the move elsewhere. The same pattern is either an emergency or a non-event depending on the rule, which is why experienced players always confirm the rule before a serious game.
The reverse situation is just as important. Under exactly-five rules, a defender who blocks carelessly may create a winning point for the attacker. If X has X X X X _ X, the gap would make six and does not win — but if the far X were not there, the same gap would make five. Removing or adding a single mark far along the line changes everything.
Counting technique
To count a line quickly and correctly:
- Start from the newest mark.
- Count outward in one direction until you hit an empty point, an opponent mark or the edge.
- Count outward in the opposite direction the same way.
- Add the two counts and the mark itself.
With a little practice this takes under a second, and it avoids the classic error of counting the same mark twice. Do it for all four directions whenever a line gets to four marks or more.
Overlines in other five-in-a-row games
Gomoku is not the only game where this question appears. Connect-style games and many online variants face the same choice between "five or more" and "exactly five". Different communities settled on different answers for the same reason: exactly-five rules make the game a little more balanced, while five-or-more rules make it simpler to explain. Neither is more "correct"; they are simply different games that share a board.
Which rule does this site use?
- Freestyle mode: five or more wins, so overlines count.
- Blocked-ends mode: the key question is whether the winning line is blocked at both ends; see the blocked-ends rule for how that works.
Both modes are available against the computer on the home board. When you play online, check which rule the game uses before the first move.
Frequently asked questions
Does six in a row win at gomoku?
In freestyle gomoku, yes. In standard gomoku, no — only exactly five wins. In renju, the first player may not make six at all.
What is an overline?
A line of six or more marks of the same player in an unbroken row.
Why is an overline forbidden in renju?
Renju restricts the first player to balance the game. Forbidding overlines for that player removes some winning shapes and gives the defender more resources.
Do overlines happen often?
Not often. They mostly appear when filling a gap between two groups on the same line.
