How to play Reversi: rules and strategy

In Reversi the lead can change hands on every move, and the player with the most discs halfway through often loses. This guide explains the rules, then the handful of ideas that separate good players from beginners.

The board and the discs

Reversi is played on an 8×8 board with 64 discs. Each disc is one colour on one side and another colour on the other. On BoardGameSite you play gold and the computer plays dark. The game starts with four discs in the four centre squares, two of each colour, placed diagonally. You move first.

Reversi dates back to 1880s England. The same rules are played today in clubs and tournaments around the world.

Making a move

On your turn, place one disc of your colour on an empty square. The move is only legal if it outflanks at least one of your opponent’s discs: there must be a straight line of their discs running from your new disc to another disc of yours, with no gaps.

Lines can run in any of eight directions: left, right, up, down or along either diagonal. Every opponent disc caught in a line flips to your colour, and if your new disc outflanks discs in several directions at once, all of them flip. Discs that are flipped during a move don’t cause any further flips themselves.

Passing and the end of the game

If you have no legal move, you must pass and your opponent plays again. As soon as you have a legal move again, you must take it. You can never pass by choice.

The game ends when neither player can move. That usually happens when all 64 squares are full, but it can come earlier if one side is wiped out or every empty square is unplayable for both. The player with more discs wins. Equal numbers is a draw.

Strategy: corners and the squares around them

Corners are the most valuable squares. A disc can only be flipped if it can be trapped between two enemy discs. A corner disc has nothing beyond it in any direction, so once you take a corner it stays yours until the end of the game. From a corner you can build along the edges with discs that become impossible to flip too. These are called stable discs.

Avoid the X-squares. The four squares diagonally next to each corner are known as X-squares. If you put a disc there while the corner is empty, you often give your opponent a way to take the corner. Leave X-squares alone unless the corner beside them is already taken, or you’ve checked carefully that your opponent can’t use it.

Be careful with the C-squares. The two edge squares directly next to each corner are C-squares. They’re less dangerous than X-squares, but they can also lead to giving up a corner.

Strategy: mobility

Beginners try to flip as many discs as possible on every move. Strong players do almost the opposite. What matters in the opening and middle game isn’t how many discs you have, but how many good moves you have, and how few your opponent has. This is called mobility.

Each disc you own is a possible target for your opponent to flank. If you own most of the board early on, your opponent has plenty of choices and you have very few. Eventually you may be forced to play onto an X-square or let them have a corner. So in the opening, prefer quiet moves that flip just one or two discs, ideally ones in the middle of your existing group.

Watch your frontier. A frontier disc is one that sits next to an empty square. Frontier discs give your opponent places to play. Moves that add few frontier discs, and keep your discs bunched in the middle, are usually good. Moves that spread your discs out along the edge of your group usually aren’t.

Strategy: edges and the endgame

Edges are strong, but not always. Edge discs can only be flipped along the edge, which makes them sturdier than discs in the middle. But taking an edge square too early can open a route for your opponent to a corner. Think about which corner each edge move affects.

Count in the endgame. With about 10 to 15 empty squares left, everything changes: now the disc count matters. Look for moves that take corners and edges, flip whole lines into stable discs, and leave your opponent with only bad options.

Try to move last. Near the end, the board often splits into small separate regions of empty squares. Getting the last move in each region usually gains discs. A region with an odd number of empty squares is one where the player who moves first there tends to get the last move too, so aim to play first in the odd regions.

Common beginner mistakes

• Flipping as many discs as possible in the opening.
• Playing next to an empty corner, especially on the diagonal.
• Taking edge squares without checking which corner it opens up.
• Letting yourself run out of moves, so you’re forced into a bad square.
• Giving up on a game that looks lost: positions can swing hugely in the last ten moves.

Reversi words to know

• Outflank: trapping a line of discs between your new disc and another of yours.
• Stable disc: a disc that can never be flipped again.
• X-square: the square diagonally next to a corner.
• C-square: an edge square directly next to a corner.
• Mobility: the number of legal moves a player has.
• Frontier disc: a disc next to at least one empty square.
• Parity: who gets the last move, overall or in a region of the board.