Connect Four, Play Against the Computer
Play Connect Four online for free, against a computer opponent with three difficulty levels or a friend in local two player mode. No download needed.
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Connect Four is one of the most recognisable strategy games in the world, a deceptively simple duel played on a vertical board of seven columns and six rows. Milton Bradley published it in 1974, based on a design credited to Howard Wexler and Ned Strongin, and it quickly became a fixture in living rooms everywhere. The concept is older than the plastic version, though: variations on the "four in a row" idea circulated for decades under names like Captain's Mistress, and the gravity twist (discs always fall to the lowest free slot in a column) is what separates it from paper games such as tic-tac-toe and gives it real tactical depth.
Frequently asked questions
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About Connect Four, Play Against the Computer
The rules take seconds to learn. Two players take turns dropping coloured discs into one of the seven columns; each disc slides down to the lowest empty cell. The first player to line up four of their own discs horizontally, vertically or diagonally wins the round. If all 42 cells fill up without a line of four, the game is a draw. In this browser version you can play against the computer, which uses a minimax search with alpha-beta pruning, or against a friend on the same device in local two player mode. A hover preview shows exactly where your disc will land, the winning four discs light up when a game ends, and the score tally is kept between rounds.
Good Connect Four play revolves around the centre column. A disc in the middle column can participate in more potential lines of four than a disc anywhere else, so claiming the centre early is almost always right. From there, the key skill is building double threats: two possible winning lines that the opponent cannot block at the same time. Equally important is defence, whenever your opponent has three discs in a row with a playable gap, you must respond immediately. Advanced players also track odd and even threats, because whether a winning cell sits on an odd or even row often decides who can force the win in a filled-up endgame.
Connect Four holds a special place in game theory because it is a solved game. In 1988, James Dow Allen and Victor Allis independently proved that the first player wins with perfect play by starting in the centre column, while opening in the outer columns actually loses against a perfect opponent. Of course, nobody plays perfectly, which is why the game stays fun. This version runs entirely in your browser, needs no account or installation, and saves your win tally locally on your device. Pick a difficulty, choose who starts, and see if you can outsmart the minimax engine.
Connect Four: The Solved Game with a Disputed Past
Toy inventor Howard Wexler, who had already licensed dozens of games, came up with Connect Four while thinking about how to make tic-tac-toe style play more interesting, and the answer was gravity. By forcing every piece to fall to the bottom of its column, the vertical frame removed the free placement of paper games and created a whole new layer of tactics. Milton Bradley launched it in 1974 and it became a massive hit. A persistent legend claims the game is centuries old and that Captain James Cook played a version so obsessively in his cabin that his crew called it the Captain's Mistress; the story is almost certainly apocryphal, but it stuck to the game and is still repeated on countless boxes and websites.
Connect Four earned a permanent place in computer science history in 1988, when it became one of the first non-trivial games to be solved twice in the same month. James Dow Allen announced a solution on October 1, 1988, and Victor Allis, then a master's student in the Netherlands, published his own independent proof just over two weeks later. Both reached the same conclusion: the first player wins with perfect play, but only by opening in the centre column. Allis's approach was especially elegant, combining nine strategic rules with a knowledge-based search, and his thesis remains a classic text for game AI students. Later brute-force work counted exactly 4,531,985,219,092 legal board positions.
The game's simple geometry has made it a favourite testbed ever since: countless university courses use it to teach minimax, alpha-beta pruning and machine learning, and in 2017 researchers even trained AlphaZero-style agents on it as a warm-up for harder games. Away from the labs, Connect Four keeps showing up in popular culture, from giant garden versions at fairs to speedrun-style competitive circuits where strong players exploit odd and even threat theory, a body of endgame knowledge deep enough that world-class matches are decided by which player controls a single square dozens of moves before the board fills.