4×4 Tic-Tac-Toe Strategy: Why Bigger Boards Need Different Thinking

On 4×4, you can't calculate everything. You have to learn to see patterns. · 9 min read

On a 3×3 board, you can hold the whole game in your head at once. There are only nine cells, eight winning lines, and twenty-six thousand or so distinct positions. A focused mind can essentially compute every relevant move.

On a 4×4 board with "need four in a row" rules, you can't. There are sixteen cells, ten winning lines, and so many positions that brute-force calculation stops working. The game shifts from calculation to pattern recognition — you have to learn to see threats and forks the way an experienced chess player sees pins and skewers, without enumerating every possibility.

This guide walks through the strategic concepts that matter on the bigger board. By the end, you should be able to play our 4×4 game with real intent rather than just guessing.

What changes on a 4×4 board

The board has 16 cells instead of 9. To win, you need four in a row instead of three. The winning lines are:

4 horizontal rows (full-row only — partial-row wins don't count)
4 vertical columns
2 long diagonals (corner to opposite corner)

That's 10 winning lines total. (The shorter diagonals — three cells from one edge to a perpendicular edge — don't count, because you need four in a row, not three.)

Compared to 3×3, the game is much longer (often 12+ moves before anything decisive happens), much more drawish (most casual games end with no one completing four in a row), and much more about pattern building than tactical calculation. Each move is less consequential individually, but the accumulation of strong/weak positions over time is what decides the game.

The geometry of 4×4 lines

Just like on 3×3, each cell on the 4×4 board is part of a different number of winning lines depending on where it is. Counting carefully:

The four innermost cells (the 2×2 in the middle) are each part of 4 winning lines (their row, their column, and possibly one diagonal — depending on position).
The four corner cells are each part of 3 winning lines (their row, their column, and one diagonal).
The eight edge cells (non-corner, non-inner) are each part of 2 winning lines (their row and their column).

The takeaway: the inner four cells are the most powerful, followed by the corners, then the edges. This is qualitatively similar to 3×3 (where center beats corner beats edge), but the inner cells now form a 2×2 block rather than a single cell. That changes the game's character significantly.

Open threes: the most important pattern on 4×4

Here's the critical pattern to learn. An open three is three of your marks in a row, with both ends of the line empty. That makes it an unblockable threat — your opponent can only block one end, and you complete the line of four on your next move.

An open three for X (top row, cells 2-3-4 with column-1 highlighted): if both flanking cells were empty, X would win next turn no matter where O blocks.

On 3×3, open threes can't really exist — the board is too small for both ends of a three to be open. (A row of three on a 3×3 board fills the whole row, leaving no ends to block.) So this concept barely matters on the small board. On 4×4 and larger, it's the central tactical idea.

The strategic implication: building an open three is essentially winning the game. So the entire mid-game is about each player trying to build an open three for themselves while preventing their opponent from doing the same. Most 4×4 games are decided by who first manages to set up an open three, or by both players carefully preventing each other from ever getting one (which leads to a draw).

Double threats: the 4×4 version of a fork

Even better than an open three is a double threat: a single move that creates two separate three-in-a-row threats at once. Just like a fork in 3×3, your opponent can only block one. Game over.

Double threats are easier to create on 4×4 than 3×3 because the board has more space. Look for cells that sit at the intersection of two of your existing lines — if you have two marks in a row going one direction and another two marks going a different direction, the intersection cell creates threats in both directions at once.

Setting up double threats is the highest art of 4×4 play. It requires planning 2-3 moves ahead. The good news: you don't have to calculate exhaustively. You just have to recognize patterns. Once you've seen a few double-threat setups, you start spotting them naturally.

Defense: counting threats

Defensively, the key skill on 4×4 is tracking how many lines each player has marks in, and how strong those lines are. Specifically, you want to count:

Lines with 3 of your opponent's marks (and no marks of yours): emergency. You must block immediately. If you have multiple such lines, you've already lost.
Lines with 2 of your opponent's marks (and no marks of yours, both ends empty): the open-three setup. You need to either block in the line itself or create a stronger threat of your own.
Lines with 2 of your opponent's marks (one end blocked by you): less urgent. Your opponent can still threaten, but only as a "closed three" — blockable on the open end.

You should also track the equivalent counts for your own lines, and aim to maximize them while minimizing your opponent's.

The defensive concept of tempo matters a lot here. If your opponent threatens an open three and you defend it, you've spent a move on defense. If instead you can create a threat of your own that forces them to defend, you've kept the initiative. Sometimes the best defense is a counter-threat — but only if your threat is at least as serious as theirs.

Why 4×4 is closer to Gomoku than to tic-tac-toe

If 4×4 strategy feels different from 3×3 strategy, that's because it really is a different game. The classic 3×3 game is essentially a tactical puzzle — small enough to solve, with a fixed set of optimal moves to memorize. The 4×4 game (and larger) is a positional game more like Gomoku (Five in a Row), a strategy game popular in East Asia where players place stones on a 15×15 or 19×19 board trying to get five in a row.

The patterns you learn on 4×4 — open threes, double threats, building "fours" with one open end — are the same patterns Gomoku players spend years mastering. Connect Four also belongs to this family, though it adds the wrinkle of gravity (pieces fall to the lowest empty cell in each column).

If you find yourself enjoying 4×4, you might also enjoy:

5×5 tic-tac-toe (also need 4 in a row) — same strategic ideas, even more room to maneuver. Available on our Big Board page via the size selector.
Connect Four — solved (first player wins by opening the center column) but still fun.
Gomoku — the full game. Surprisingly deep, played seriously in tournaments.

The bigger the board, the more the game rewards intuition over calculation. Some players find this freeing (less to memorize, more space to be creative); others find it frustrating (no clear "best move" to know). It's a matter of taste, but it's worth trying both styles to discover which you prefer.

Switch to 4×4 mode on our Big Board game and try the strategies above. The Medium AI is forgiving; Hard will punish loose play.

Play 4×4 →