Play Connect Four Online for Free
Connect Four is the disc-dropping duel where every move is a small act of gravity. Played on a standing 7-column, 6-row grid, you and your opponent take turns sliding colored discs into open columns, each one tumbling to the lowest empty slot. Red always drops first, and the race is on to line up four of your own discs in a row — across, up, or on either diagonal — before your opponent does the same. The catch is that you never choose the exact square, only the column, so every threat is shaped by the stack beneath it.
How to Play Connect Four
Connect Four is a two-player game on a vertical grid that is 7 columns wide and 6 rows tall. One side plays red discs, the other plays yellow, and red always takes the first turn. On your turn you pick any column that is not already full; your disc drops straight down and settles on the lowest empty slot in that column. You can never place a disc in mid-air or choose its exact height — gravity decides the row for you.
You win the instant you connect four of your own discs in an unbroken line. That line can run horizontally along a row, vertically up a single column, or diagonally in either direction. The engine checks all four orientations after every drop, so a sneaky diagonal counts exactly the same as an obvious horizontal four. There is no limit on how many discs each player has — you keep dropping until someone connects four or the board runs out.
If all 42 slots fill up and neither player has made four in a row, the game is a draw. There are no captures, no removing discs once they land, and no passing — every turn you must drop somewhere. You can play against the computer at three difficulty levels or share one device with a friend in local two-player mode, and an undo button lets you take back your last move while you are learning.
Connect Four Tactics: Threats, Traps, and Parity
Open in the center column and keep fighting for it. The center is the single most valuable file on the board because more potential four-in-a-row lines pass through it than through any other column — this site's AI even hard-codes a bonus for every disc it owns there. If you go first, drop in the middle; if your opponent grabs it, take a column right beside it and contest the center on your next turn.
Win by building a double threat — two separate ways to make four that share no single blocking square. Since your opponent can only answer one threat per turn, a genuine double threat is unstoppable. The classic example is an open-ended row of three (the 'seven trap'): three of your discs in a row with a playable empty slot on both ends, so blocking one end just hands you the other. Diagonals are the easiest threats to overlook, so hunt for diagonal doubles your opponent isn't watching.
Think in terms of odd and even rows. Because discs stack from the bottom and red moves first, the first player naturally tends to complete threats on the odd rows (1, 3, 5 counting from the bottom) while the second player gets the even rows. If you went first, aim to set your winning square on an odd row; if you went second, steer your decisive threat onto an even row. This parity idea is what separates casual play from consistently winning.
Watch what you give away. Never drop a disc directly beneath a square your opponent needs to win — that move just lifts their winning slot into reach on their next turn. Conversely, you can use 'stacked' threats to force the issue: place a threat one row above an empty slot so that when your opponent is forced to fill the slot below, your win lands on top. Against the Hard AI, which searches six moves deep and never plays a random move, you will need these forcing sequences rather than hoping it overlooks a simple three-in-a-row.
Frequently Asked Questions
Do diagonal lines of four really count as a win here?
Yes. The engine checks horizontal, vertical, and both diagonal directions after every disc lands, so four in a row on either diagonal wins exactly like a horizontal or vertical line. Diagonal threats are the ones players miss most often, both when attacking and when defending.
Who goes first, and does that decide the game?
Red always drops first. Connect Four is mathematically solved — with flawless play the first player can force a win by opening in the center column. In practice, perfect play is extremely hard, so going first is an edge rather than a guarantee, especially against the medium and hard AI.
Can I take a disc back or remove one from the board?
Discs are permanent once they land — there are no captures and no removing pieces mid-game. However, there is an undo button that lets you take back your most recent move, which is handy for studying lines or recovering from an obvious slip.
What happens if the whole board fills with no four in a row?
It is a draw. The board has 42 slots, and if every column fills without either color connecting four, neither player wins. There is no passing and no tiebreaker — a full board with no line is simply a tie.
How do the three AI difficulty levels actually differ?
All three use the same minimax search but with different depth and randomness. Easy looks only two moves ahead and plays a random move about a third of the time, Medium searches four moves deep and blunders only rarely, and Hard searches six moves deep, favors the center, and never plays a random move — so it punishes loose threats hard.