Connect Four
Play the classic four-in-a-row game free in your browser — against a smart computer on three difficulty levels, or a friend in 2-player mode. Unlimited undo, winning-line highlight, no signup.
How to Play Connect Four
- 1Pick vs Computer (Easy/Medium/Hard) or 2 Players.
- 2Click a column to drop your disc — it falls to the lowest empty slot.
- 3Line up four of your colour in a row — across, up, or diagonally.
- 4Block your opponent's three-in-a-row, and use Undo to explore ideas.
The Rules, in Short
Connect Four is played on a vertical grid seven columns wide and six rows tall — forty-two slots in all. Two players each own a colour (here, red and yellow) and take turns dropping one disc per turn into any column that is not yet full. Gravity does the rest: the disc settles on top of whatever is already in that column. The first player to form an unbroken line of four of their own discs — horizontally, vertically, or along either diagonal — wins immediately. If every slot fills without a line of four, the game is a draw.
It sounds simple, and the rules truly are, but underneath sits a surprising amount of tactics. Every disc you drop changes which squares your opponent can safely use next, so a game of Connect Four is really a running battle over space and threats.
Playing Against the Computer
The computer opponent comes in three strengths. Easy plays sensibly and will always take an obvious win or block an obvious threat, but it does not plan far ahead — a good level for children and newcomers. Medium looks a few moves into the future and punishes loose play. Hard runs a deeper minimax search with alpha-beta pruning, weighs the whole board, and favours the centre, so it plays a strong, consistent game. Every level shares two guarantees: it will take a winning move the instant one appears, and it will block yours whenever you threaten four — so cheap wins are off the table and you have to genuinely out-think it.
Winning Strategy
A handful of ideas will lift your game quickly. Take the centre — the middle column touches the most possible fours, so a disc there is worth more than one on the edge. Create two threats at once. The winning tactic in Connect Four is the “double threat”: a move that makes two separate three-in-a-rows so your opponent can only block one. Watch the odd and even rows — advanced players count which rows their threats sit on, because the player moving first tends to benefit from threats on odd rows and the second player from even ones. And always scan for the opponent's three-in-a-row before you play your own plan; one missed block ends the game.
Quick Tips
Control the centre
Play the middle column early. Central discs take part in the most winning lines and keep your options open.
Build a double threat
Aim to create two three-in-a-rows at once. Your opponent can only block one, so the other one wins.
Always block a three
Before playing your own plan, check whether the opponent has three in a row with an open end — and block it.
Don't set up their win
Avoid playing directly below a square that lets your opponent complete a four on their next drop.
Think in columns
Every disc raises the landing spot in that column by one. Plan how a drop changes what both players can reach.
Learn with Undo
Take a move back to see how the computer reacts to different lines. It's the fastest way to improve.
Frequently Asked Questions
How do you play Connect Four?
Two players take turns dropping coloured discs into a seven-column, six-row grid. Because of gravity, each disc falls to the lowest empty slot in the column you choose. The goal is to be the first to line up four of your own discs in a row — horizontally, vertically, or diagonally. If the whole board fills with no four-in-a-row, the game is a draw.
Can I play Connect Four against the computer?
Yes. The default mode is you versus the computer, with Easy, Medium, and Hard levels. The computer always takes a winning move when it has one and always blocks your winning move when you threaten one; on Hard it looks several moves ahead using a minimax search, so it plays a genuinely strong game. Switch to 2 Players to play a friend on the same device.
Does the first player always win?
In theory, yes — Connect Four is a solved game, and with perfect play the player who moves first can force a win by starting in the centre column. In practice, though, almost nobody plays perfectly, so games are competitive. Our Hard computer plays very well but is not a perfect solver, so a strong human can still beat it.
What is the best first move in Connect Four?
The centre column. Discs in the centre take part in the most possible four-in-a-rows — horizontal, vertical, and both diagonals — so controlling the middle gives you the most winning chances and the most flexibility. The computer opens in the centre on Hard for exactly this reason.
Can I undo a move?
Yes, there is unlimited undo. In computer mode, undo steps back past the computer’s reply so it is your turn again, letting you rethink a line. It is a great way to learn — try a move, see how the computer responds, and take it back to explore a better plan.
Does it work on mobile?
Yes. The board scales to your screen and you drop a disc by tapping a column. Everything runs in your browser with nothing to install, and no data is uploaded — you can play offline once the page has loaded.
Want the deeper strategy? Read our full guide on how to win at Connect Four.