Connect Four Strategy: Play Like It's Solved

A game that's been solved

Connect Four looks casual, but it is one of the few games that has been completely solved by computers: with perfect play, the first player can always force a win by starting in the centre column. That does not make it boring — almost nobody plays perfectly — but it does mean there is a right way to think about the game. Learn a few principles and you will beat most opponents comfortably, and give a computer a real fight. Practise them in theConnect Four game, which plays a look-ahead opponent.

Principle one: own the centre

Every disc you place can contribute to horizontal, vertical, and both diagonal lines — but only if it sits where those lines cross. The centre column participates in more possible four-in-a-rows than any other, which is why it is the strongest opening and why control of the middle tends to decide games. Aim to place your early discs in or near the centre, and be wary of letting your opponent stack the centre uncontested. If you are the first player, your very first move should almost always be the middle column.

Principle two: think one move ahead — always

The most common way to lose is to make your own threat while ignoring your opponent's. Before every move, scan for two things: can I make four this turn, and can my opponent make four next turn? If they have three in a row with an open end, you usually must block it — unless you can win outright first. Training yourself to check the opponent's threats before pursuing your own plan eliminates the majority of losses.

Principle three: create double threats

A single threat is easy to block. The winning idea is the double threat — a position where you threaten to complete four in two different places at once. Your opponent can only block one of them per turn, so the other wins. Double threats are usually built by combining lines that share a disc: a horizontal three that also feeds a diagonal, for example. Much of high-level Connect Four is manoeuvring to reach a position where a single move opens two threats simultaneously.

The odd/even threat trick

This is the concept that decides games between strong players, and it sounds stranger than it is. Number the rows from the bottom: row 1 (bottom) is odd, row 2 is even, and so on. Because players alternate and discs stack from the bottom, whoever is going to occupy a given square is partly determined by its height. In classic theory, the first player benefits from odd threats (winning squares on odd rows) and the second player from even threats. A practical takeaway for the first player: aim to build threats that complete on odd rows, and you will often find the game falls into place in the endgame as columns fill up. You do not need the full theory to benefit — just knowing that the height of a winning square matters, not only its column, puts you ahead of most opponents.

Traps to avoid

• Setting up your opponent. Filling a square directly below your opponent's winning square hands them the win. Watch what your move enables on top of it.
• Tunnel vision. Chasing your own three-in-a-row while the opponent quietly builds a double threat elsewhere.
• Ignoring diagonals. Diagonal fours are the easiest to miss for beginners, both to make and to block.
• Wasting the centre. Giving up central control early cedes the position that feeds the most winning lines.

The story of solving Connect Four

Connect Four holds a notable place in computing history: in 1988 it was independently solved by James Allen and Victor Allis, making it one of the first non-trivial games proven to have a perfect strategy. Allis's solution, part of his master's thesis, showed that the first player wins with best play — but only by starting in the centre column. Start anywhere else and the game is at best a draw against perfect defence; start in an outer column and the second player can actually win. That single opening move is the difference between a forced win and a forced loss.

The board has roughly 4.5 trillion legal positions, far too many to check one by one with 1980s hardware, so the solutions relied on clever pruning and knowledge-based rules rather than brute force. Today the game is fully solved by modern computers in seconds, and databases exist that will tell you the exact outcome of any position with perfect play from both sides. None of this spoils the game for humans — nobody plays perfectly — but it does mean the strategic advice in this guide has a firm mathematical foundation rather than being mere opinion.

How the computer opponent thinks

The AI you play against here uses minimax with alpha-beta pruning, the classic algorithm behind most board-game engines. Minimax works by assuming both players play optimally: the computer looks ahead several moves, considering its best replies to your best replies, and picks the move that leads to the strongest position it can force regardless of what you do. Each end position is given a numeric score — winning is enormously positive, losing enormously negative, and everything in between is judged by counting threats and favouring central control.

The "alpha-beta" part is an optimisation that makes this practical. As the search explores, it keeps track of the best result each side is already guaranteed, and abandons any branch that clearly cannot beat it. This prunes away huge portions of the tree without changing the answer, letting the engine search meaningfully deeper in the same time. It is why a small amount of code can look several moves ahead and reliably punish a careless human — and also why searching one move deeper makes an engine noticeably stronger.

Openings and the shape of a game

Connect Four games tend to follow a recognisable arc. The opening is a fight for the centre: both players stack the middle columns, since discs there feed the most potential lines. The middlegame is where threats are built and blocked, and where most games are actually decided — this is the phase to watch for double threats forming. The endgame, as columns fill, becomes almost forced: with few legal moves left, whoever set up the right odd or even threat wins by simple counting.

A practical implication is that early moves matter more than they look. Playing an outer column in the opening "to be clever" typically just cedes the centre for nothing. Similarly, avoid making a move that fills a square directly beneath a spot where your opponent would complete four — a very common way to hand over a game. Thinking about what your move enables above it is a habit that separates decent players from good ones.

Getting better, deliberately

The fastest way to improve is to change what you pay attention to. Before each move, run a short mental checklist: can I win now, can they win next, and does my move create or allow a threat? Most losses come from skipping step two. Beyond that, try playing a few games where you deliberately give up your own attack to build a solid, threat-free position — it teaches you to see the board defensively, which is the weaker half of most players' game.

Finally, use the computer as a training partner rather than an obstacle. Losing to an engine is informative: replay the moment it gained the advantage and work out which of your moves allowed it. Because Connect Four is small enough to hold in your head, this kind of review genuinely sticks — and once you can beat the engine going first, switching to play second is a much sterner test that will sharpen your defence considerably.

The race to solve it

Connect Four was published commercially in 1974, and for a decade nobody knew whether the first player could force a win. The answer arrived in 1988, independently and within weeks of each other, from two researchers: James Allen and Victor Allis. Allis's master's thesis went further, describing a knowledge-based program called VICTOR that could play perfectly using nine strategic rules rather than raw search — proving that the game is a first-player win with the opening move in the centre column.

The scale of that achievement is easy to underestimate. The standard 7 × 6 board has roughly 4.5 trillion legal positions. Solving it meant proving a result across that entire space, at a time when computers were vastly slower than a modern phone. Today the game is "strongly solved," meaning the optimal move is known from any position, and free solvers can tell you instantly whether a given board is winning, losing or drawn with perfect play. None of this diminishes the game between humans — nobody plays perfectly, and the whole art lies in the mistakes.

Reading a game: notation and openings

Serious players record games with a simple notation: columns are numbered 1 to 7 from the left, and a game is just the sequence of columns played. So "4433" means both players opened in the centre, then both played column 3. Because the board is symmetric, columns 1 and 7 are equivalent as opening moves, as are 2 and 6, and 3 and 5 — which is why opening theory only really discusses four distinct first moves.

That table is worth absorbing, because it makes the centre principle concrete: opening in the middle is the only first move that preserves a forced win, and opening on an edge column actually hands the win to your opponent. If you take one piece of theory away, make it "always start in the centre."

Practising against an engine

A computer opponent is an unusually good teacher for this game, because Connect Four is small enough that you can actually understand why you lost. When the engine beats you, replay the game and look for the move where your position went from balanced to lost — it is almost always a single moment: a missed block, a disc played on an edge for no reason, or filling a square that handed the opponent the winning cell above it.

A good progression is to first learn to beat the engine consistently while playing first, which mostly means taking the centre and never missing a block. Then switch to playing second, which is a much sterner test: with correct play from the first player you cannot win, so your goal becomes holding the draw — punishing any inaccuracy and defending precisely. Players who can reliably draw as the second player have genuinely internalised threat-counting, and at that point beating most human opponents becomes routine.

A checklist for every move

When you are learning, it helps to run the same short mental routine before each disc. It takes seconds and eliminates the overwhelming majority of losses at beginner and intermediate level.

• Can I win right now? Scan all four directions for three of your own with an open, reachable end. If yes, play it — nothing else matters.
• Can they win next move? Do the same scan for your opponent. If they have a live three, block it unless you win first.
• Does my move hand them the square above? Every disc you place creates a new landing square directly on top. Check what your opponent could do with it.
• Am I still contesting the centre? If the middle columns are filling with their colour, prioritise getting back in.
• Am I building toward two threats? Look for moves that extend two potential lines at once rather than just one.

The third item is the one beginners skip, and it is responsible for a huge share of surprise losses. Filling a square that completes your opponent's winning cell above it is the Connect Four equivalent of a self-inflicted wound — the move looked harmless, and it lost the game on the spot. Simply asking "what sits on top of this?" before every placement will win you games immediately.

Connect Four rewards a simple discipline: hold the centre, check your opponent's threats before your own, and work toward a move that threatens twice at once. Put it into practice against the computer in theConnect Four game— and once you can beat it going first, try winning as the second player, which is a far tougher test.