Play Othello (Reversi) Online

Play Othello against the computer in your browser—no download, no sign-up. You play Black; the computer plays White. Choose a difficulty and try to finish with more pieces than the AI.

What Is Othello?

Othello (also called Reversi) is a two-player strategy game on an 8×8 board. Each player has pieces of one color (black or white). You take turns placing one piece per turn. Placing a piece can flip one or more of the opponent’s pieces to your color when they are trapped between your new piece and another of your pieces in a straight line.

How to Play

1. Black moves first. Click any square that shows a valid move (highlighted with a small dot).
2. A move is valid only if it flips at least one white piece in a straight line (horizontal, vertical, or diagonal).
3. After your move, all white pieces that are now bounded by your black pieces in any direction are flipped to black.
4. Then it’s the computer’s turn (White). It will play automatically after a short “Computer thinking…” delay.
5. If you have no valid moves, your turn is skipped and the computer plays again. If both players have no valid moves, the game ends.
6. Winner: The player with more pieces when the game ends. A draw is possible if the counts are equal.

Board and Rules Summary

• 8×8 grid with four pieces in the center at the start: White at (3,3) and (4,4), Black at (3,4) and (4,3).
• You can only play on empty squares that form at least one line of opponent pieces between your new piece and an existing piece of your color.
• All 8 directions count: up, down, left, right, and the four diagonals.
• Pieces flip only when bounded in a straight line—every opponent piece in that line (until your piece) flips.

Difficulty Levels

• Easy – The computer picks a random valid move. Good for learning the rules.
• Medium – Minimax AI with depth 3. Stronger but beatable.
• Hard – Minimax with depth 5. Quite strong.
• Expert – Minimax with depth 6 and a better evaluation (corners, edges, mobility). Very challenging.

You can change the difficulty from the dropdown above the board; it applies from the next game or when you click Restart.

Tips

• Corners are very valuable—they can’t be flipped. Try to get them when it’s safe.
• Edges are also strong; avoid giving the opponent easy access to corners.
• Having more valid moves than the opponent (mobility) is often a good sign.
• Don’t flip too many pieces early if it gives the opponent a corner or a strong edge.

Good luck, and enjoy the game.