Play Connect Four strategy game free in your browser. Drop discs to connect 4 in a row vs AI. No download required.
Two players alternate dropping colored discs into a seven-column, six-row vertical grid. A dropped disc falls to the lowest available position in that column. Win by placing four of your discs in a connected line horizontally, vertically, or diagonally. The game ends in a draw if all 42 positions are filled without either player achieving four in a row. Choose your column by clicking it or pressing the corresponding key.
The fundamental winning technique is creating a double threat: two separate lines of three that both need only one more disc to complete, positioned so your opponent can block only one per turn. Setting up a double threat requires building multiple partial lines simultaneously rather than pursuing a single four-in-a-row. Avoid completing three-in-a-rows that can be blocked from both ends, since those lines die without contributing. Build toward positions where your opponent's block of one line completes another.
Connect Four was mathematically solved in 1988, independently by James Dow Allen and Victor Allis. Both proofs demonstrated that the first player can always force a win with perfect play, starting with the center column. Despite being solved, the game remains popular because the tree of variations is too large for most human players to calculate in real time, preserving genuine uncertainty in casual play. It has been sold as a physical board game since 1974 and remains one of the most commonly owned family games in North American households.
The opponent here is not random; it runs a minimax search with alpha-beta pruning, looking several moves ahead and scoring each possible board. It explicitly values the center column and counts how many of its own pieces sit in open four-in-a-row windows versus yours, then picks the column with the best look-ahead outcome. Practically, this means the AI will always take an immediate win if you leave one available and will always block your three-in-a-row if it sees the threat within its search depth. To beat it, you cannot rely on a single sneaky line, it will spot and block that. You must build two threats at once so its one blocking move cannot stop both. Because it weights the center heavily, contesting the middle column early denies it the position from which the most winning lines radiate, and it forces the AI onto the back foot.
Beyond simple double threats, strong Connect Four play uses parity. On the seven-by-six board, columns fill from the bottom up, so the row a winning piece lands on is partly forced by how many discs sit beneath it. A classic principle from the game's solution is that the first player benefits from threats on odd rows counting from the bottom, while the second player benefits from even-row threats. When you set up a vertical or diagonal three, notice which row the completing disc would occupy. If you are first to move, aim your unstoppable threat at an odd square, because zugzwang late in the game tends to hand you that square. This is why expert players sometimes refuse a tempting block and instead preserve a well-placed threat, trusting parity to deliver the winning drop once the board fills.
It uses minimax with alpha-beta pruning, searching several moves ahead and scoring each board by center control and open four-in-a-row windows. It will always grab an immediate win and block any of your threats that fall inside its search depth.
A double threat is two separate three-in-a-rows that each need one more disc, placed so a single move cannot block both. Since players drop only one disc per turn, the opponent stops one line and you complete the other next turn.
Yes. Connect Four was solved in 1988, proving the first player can force a win with perfect play by starting in the center column. The second player can only force a draw if the first player makes a mistake.
The center sits in the most possible winning lines, horizontal, vertical, and both diagonals, so a disc there contributes to more threats than an edge piece. The AI also weights it heavily, so taking it early limits the opponent's best options.
Because columns fill bottom-up, the winning disc lands on a forced row. The first player tends to benefit from threats on odd rows from the bottom, the second from even rows. Late-game zugzwang often forces the opponent to hand you that square.