How to Play Reversi
Reversi is played by two players on an 8x8 board with 64 identical discs, black on one side and white on the other. You place one disc per turn, and any line of opponent discs you trap turns over to your colour. When the game ends, the player with more discs on the board wins.
The board and the starting cross
Columns are labelled A to H and rows 1 to 8. The game starts with four discs placed diagonally in the centre: White on D4 and E5, Black on E4 and D5. Black always moves first, and has exactly four legal opening moves: D3, C4, F5 and E6.
Outflanking in 8 directions
A move is legal only if the new disc traps at least one opponent disc. In one of the eight directions (up, down, left, right or one of the four diagonals) there must be an unbroken line of opponent discs with one of your own discs at the far end. Every trapped line flips at once, in every direction that qualifies. An empty square breaks a line, and a line that runs to the edge without reaching your disc does not flip.
No legal move? Your turn is passed automatically
If no empty square would flip at least one disc for you, you cannot move and your turn is passed. Your opponent moves again, and play comes back to you as soon as you have a legal move. You may never pass while a legal move exists. On this site the pass happens on its own and a notice tells both players.
How the game ends and who wins
- The game ends when all 64 squares are filled.
- It ends at once if one player has no discs left (a wipeout).
- It ends early when neither player has a legal move, even with empty squares left.
- Then count the discs: the player with more discs on the board wins. Equal counts are a draw.
Winning Strategy: Corners, X-Squares and Mobility
Beginners try to flip as many discs as they can on every move. Strong players do almost the opposite: they care about which squares they hold and how many moves they keep for themselves, not about the score in the middle of the game. Three ideas carry most of the weight.
Why the corners are king: A1, H1, A8 and H8
A disc in a corner can never be flipped. No line can pass through a corner to trap it, because there is no square beyond it. Discs that can never be flipped again are called stable discs, and they are the only points that are truly safe until the final count.
A corner also anchors its two edges. Once you own A1, an unbroken run of your discs along row 1 or column A from that corner is stable too, and the stable area keeps growing as you extend it. Many games are decided by who takes the first corner and the edges beside it.
Avoid the X-squares and C-squares while the corner is empty
The X-squares are the four squares diagonally next to a corner: B2, G2, B7 and G7. A disc there while the corner is still empty usually hands the corner to your opponent, who only has to trap it along the diagonal.
The C-squares are the edge squares right beside a corner. They are less dangerous than X-squares but can still give a corner away, especially while the rest of that edge is unsettled. Once a corner is taken, its X- and C-squares stop being dangerous.
- X-squares: B2, G2, B7, G7. Stay off them until the nearby corner is taken.
- C-squares: B1, A2, G1, H2, A7, B8, H7, G8. Play them only when the corner is safe.
Flip fewer discs early: the mobility strategy
Mobility is the number of legal moves you have. In the first 20 moves or so, keeping your disc count low and your discs in the middle leaves your opponent few discs to trap. They run out of good moves and are forced onto X-squares, C-squares and other bad squares.
Prefer quiet moves that flip one or two inner discs over big flips that build long walls. A wall of your discs is a row of targets for your opponent; a small, compact group gives them almost nothing to aim at. Grab discs near the end, when every square is counted.
Reversi FAQ
Is Reversi Online free to play?
Yes. Every mode is free and needs no account, download or sign-up. The site is supported by ads.
Who moves first in Reversi?
Black always moves first. Against the AI you can take Black to open, or White to let the AI open. In an online rematch the players swap colours, so the other player gets Black.
What happens if I have no legal move?
Your turn is passed automatically and your opponent moves again. The game only ends early if neither player can move. You cannot pass while you still have a legal move.
How do you win a game of Reversi?
Have more discs on the board than your opponent when the game ends: when the board is full, when one side has no discs left, or when neither side can move. Equal counts are a draw.
How strong is the Grandmaster AI?
It searches six moves ahead with alpha-beta pruning and weighs corners, stable discs, mobility and dangerous squares. With ten or fewer empty squares it calculates the exact final score of every move, so it rarely loses an endgame. Medium looks four moves ahead using square weights, and Easy simply grabs the most discs.
How do I play Reversi with a friend online?
Choose Play with a Friend, create a private room and send the invite link, which ends in ?room= and a six-character code. The game starts when your friend opens it. Each move has a 20-second clock.
What does "Start Immediately with AI" do?
While Online Quick Match is looking for an opponent, this button leaves the queue and starts a game against the AI on the same board right away, without reloading the page.
Can I play Reversi on my phone?
Yes. The board fits any screen. On a touchscreen, the first tap on a square shows which discs would flip and the second tap places your disc.