Caro vs Gomoku: What's the Difference?

Short answer: Caro is the Vietnamese name for five in a row, so in the broadest sense Caro and Gomoku are the same game. In practice, "Caro" usually means five in a row played with a blocked-ends rule: a line of five that is sealed by the opponent at both ends does not count. That one rule changes how attacks and defences work, so Caro and freestyle Gomoku play noticeably differently.

What "Caro" means

In Vietnamese, caro describes a checked pattern — the grid of squares the game is played on — and the game is called cờ caro. It is commonly played on squared notebook paper with a pen, one player drawing X and the other O, rather than with stones on a board.

Because it is a game people learn from each other rather than from a federation rulebook, Caro rules are passed on informally, and details vary between groups and between online sites. When someone says "let's play Caro", it is worth asking which rules they mean.

What Gomoku is

Gomoku is the name, borrowed from Japanese, under which five in a row is known internationally: two players alternate placing stones, and the first to make five in a row wins. It has well-defined variants — freestyle, standard and Renju — and an international competitive scene. Our introduction to Gomoku covers the basics.

Are Caro and Gomoku the same game?

They share the same goal, the same turn structure and almost all of the same tactics. A good Gomoku player is a good Caro player and vice versa. The differences are in a few rules, and those rules depend on who you are playing with:

• If your Caro group plays without the blocked-ends rule, you are effectively playing freestyle Gomoku with X and O.
• If they play with it, you are playing a recognisably different variant, with different defensive resources.

Rule differences at a glance

	Freestyle Gomoku	Caro (common rules)
Board	15×15, sometimes 19×19	Often an open paper grid; online boards vary
Pieces	Black and white stones on intersections	X and O in squares
Who starts	Black	Agreed by the players (X on 5Row)
Winning line	Five or more in a row	Five in a row that is not blocked at both ends
Overline (six or more)	Wins	Varies by group and source
Forbidden moves	None	None
Opening rule	None in casual play	None

Sources do not agree on every detail of Caro. Some describe the winning five as one "not blocked at either end"; others describe a five that is blocked at both ends as the only kind that fails. The second reading — a five needs at least one open end — is the one 5Row implements.

The blocked-ends rule

Vietnamese players call it luật chặn hai đầu, the two-end (blocked at both ends) rule. Under it, a five that has an opposing piece on both sides does not win:

On 5Row, only opposing marks block an end — the edge of the board does not, so a five that runs into the edge still wins. A line of six or more always wins, even with both ends sealed:

How the rule changes play

The blocked-ends rule mainly strengthens the defender:

• Some fours stop being threats. A four squeezed into exactly five free points between two opposing pieces can only ever produce a sealed five, so it can be ignored. In freestyle Gomoku the same four must be blocked.
• Defenders can block in advance. A piece that leaves an attacker's line with only five points of room makes it harmless before it ever becomes a four.
• Open space matters more. Attacks need room on at least one side of the final five. Lines in the open middle of the board are worth more than lines near edges or near opposing pieces.
• Overlines become a resource. On 5Row, pushing a line to six wins regardless of the ends.

The Gomoku tactics guide shows how this affects specific threat shapes, including which fours stay dangerous.

Overlines

What happens with six in a row is one of the least consistent parts of Caro. Some describe overlines as not counting at all; others treat six as a win that ignores the blocked-ends rule. Freestyle Gomoku counts six as a win, standard Gomoku does not. If you play Caro outside 5Row, agree on this before the game. On 5Row, six or more always wins.

Forbidden moves

Neither Caro nor freestyle Gomoku has forbidden moves: either player may make a double three, a double four or an overline. Forbidden moves are a feature of Renju, which restricts the first player to balance the game. Our Gomoku vs Renju comparison explains those restrictions.

How Caro relates to Renju

Caro and Renju both modify Gomoku, but in different ways and for different reasons. Renju is a formal competitive game: it limits only Black's moves and uses fixed opening rules, all aimed at offsetting the first-move advantage. Caro's blocked-ends rule applies to both players equally and comes from informal play. It does make defending easier, but it does not single out the first player.

Names across regions

The same family of games appears under different names:

• Gomoku — the international name, from Japanese.
• Five in a row — the plain English description.
• Caro / cờ caro — Vietnam.
• Omok — Korea.
• Wuziqi (五子棋) — China.
• Gobang — an older English name.

These names usually describe the core game, not a precise rule set. "Caro" is the one most closely tied to a specific rule, the blocked-ends rule.

Which rules does 5Row use?

5Row is built on freestyle Gomoku, with Caro's blocked-ends rule available and on by default:

• 19 columns by 15 rows of squares; X moves first.
• Five or more in a row wins, in any direction.
• With the two-end rule on, an exact five blocked at both ends by O marks does not win. The board edge is not a block, and six or more always wins.
• No forbidden moves and no opening rule.

You can switch the rule off in practice games, or change your default in Settings; online matches use the setting chosen when the match is created. The full list is in our Gomoku rules guide, and how to play Gomoku walks through a complete game.

FAQ

Is Caro easier or harder than Gomoku?

Neither — it is different. The blocked-ends rule gives the defender more options, so attacks need more space and more preparation. Many players find that it rewards patience.

Do Gomoku tactics work in Caro?

Almost all of them. Threes, fours and double threats work the same way; you just need to check that the final five would have at least one open end.

Does the edge of the board count as a block?

On 5Row, no. Only an opponent's mark blocks an end, so a five that reaches the edge wins even if an O sits at its other end. On paper, the question rarely comes up because the grid is usually larger than the game.

Can I play without the blocked-ends rule on 5Row?

Yes. Turn off the two-end rule in a practice game or in Settings before you create a room or look for a match. The rule shown in the top bar is the one the match uses.