Endgame in Connect Four

The endgame in Connect Four begins when roughly two-thirds of the board is filled. At this point, the game changes character dramatically. In the opening and midgame, you have many columns to choose from. You can build new threats, switch plans, and respond flexibly. In the endgame, most columns are nearly full. Each move has fewer alternatives. The game becomes more like a forced sequence of plays where small positional advantages decide everything.

Odd-even theory dominates the endgame. As columns fill up, the turn order determines who plays into which squares. If you are player 1 and you have a threat on an odd row, the natural flow of the game tends to deliver that row to you at the right moment. Your opponent fills the even rows below your threat on their turns, and you get the odd row on yours. Understanding this parity is essential for endgame play. Without it, you are guessing. With it, you can calculate the outcome several moves in advance.

Counting remaining moves is a critical endgame skill. Look at each column and count the empty squares. Calculate the total number of moves remaining in the game. Determine whether the last move will be made by player 1 or player 2. This tells you who is "filling" the board. The player who makes the last move fills more squares overall, which affects which threats get activated. If 15 moves remain, player 1 makes 8 of them (moves 1, 3, 5, 7, 9, 11, 13, 15) and player 2 makes 7.

Practical endgame tips: avoid playing in columns where your opponent has threats above your position. Look for columns where you can safely play without enabling an opponent's win. When both players have threats, the one whose threat sits on the "right" row (matching their parity) usually wins. If you are losing the endgame parity battle, your only hope is to create a direct threat that wins before the parity advantage kicks in. Speed beats parity if you can win first. Otherwise, the patient player with correct parity wins the war of attrition.