Connect Four Solver

Is Connect Four Solved?

Yes. Connect Four was independently solved by James Allen and Victor Allis in 1988. They proved that with perfect play, the first player always wins by starting in the center column (column 4). If the first player starts anywhere else, the game is either a draw or a second-player win.

In 1995, John Tromp strongly solved the game by computing the exact value of every reachable position. This means for any board state, we know whether it leads to a first-player win, a second-player win, or a draw with best play from both sides.

What Does "Solved" Mean?

A solved game is one where the outcome can be determined from any position, assuming both players play optimally. Connect Four has approximately 4.5 trillion possible positions. The solver has evaluated all of them.

This doesn't mean the game is boring. No human can memorize 4.5 trillion positions. Even the two solvers of the game, when they played each other in 1995, drew their six-game match 3-3. Knowing a game is solved and playing it perfectly are very different things.

How the Solver Works

The engine evaluates positions using alpha-beta pruning with a transposition table built from the complete game solution. At lower difficulty levels, it limits its search depth to simulate human-like play. At maximum difficulty, it accesses the full solution and plays the provably best move in every position.