Reversi (also known as Othello) is one of the greatest abstract strategy board games ever devised. Now you can play Reversi free online in your browser against a challenging AI opponent — no download, no app, no login required. The game is played on an 8×8 board with discs that are black on one side and white on the other. You play as Black and move first. On each turn, you place a disc to "outflank" one or more of your opponent's discs — trapping them in a straight line (horizontal, vertical, or diagonal) between your newly placed disc and another disc of your color. All outflanked discs are flipped to your color. The beauty of Reversi lies in its dramatic reversals. A player who appears to be losing can suddenly flip dozens of discs in a single move. Corner squares are especially powerful because they can never be flipped once captured. The AI uses advanced minimax search with alpha-beta pruning to provide a genuine strategic challenge — you will need to think several moves ahead to win.
How to Play Reversi
The game starts with four discs in the center of the board — two black and two white in a diagonal pattern. Black (you) always moves first.
On your turn, place a disc on any empty square that outflanks at least one of the AI's discs. Outflanking means your new disc and an existing disc of your color form a straight line (horizontal, vertical, or diagonal) with one or more opponent discs in between. All outflanked discs are flipped to your color.
Valid moves are shown as subtle green dots on the board. If you have no valid moves, your turn is automatically passed. The game ends when neither player can move. The player with the most discs on the board wins.
Key strategic concepts: corners are the most valuable squares (they can never be flipped), edges are strong positions, and the squares adjacent to corners (especially diagonals) can be dangerous to occupy early. Sometimes having fewer discs in the midgame gives you more moves later — a concept called "mobility."
Reversi Tips & Strategies
- Prioritize capturing corners — they can never be flipped and anchor your position for the entire game.
- Avoid placing discs on squares diagonally adjacent to empty corners (X-squares) — this often gives your opponent the corner.
- In the early and mid game, try to have fewer discs but more available moves. Mobility beats disc count until the endgame.
- Edge squares are strong but not as powerful as corners. Secure edges only when you can control the adjacent corner too.
- Try to force your opponent into positions where they have very few moves — this gives you control of the board.
- In the endgame (last 10-15 moves), disc count becomes everything. Maximize flips in the final moves.
Frequently Asked Questions
What is the difference between Reversi and Othello?
Reversi and Othello follow essentially the same rules. Othello is a trademarked version of Reversi that standardized the starting position (four discs in the center) and the rule that Black always moves first. Our game uses these standard Othello rules.
How strong is the AI opponent?
The AI uses minimax search with alpha-beta pruning at depth 5, increasing to depth 6-8 in the endgame. It evaluates positions based on disc placement, corner control, and mobility. It provides a strong challenge for intermediate players and a good training partner for advanced players.
What happens when I have no valid moves?
If you have no legal moves on your turn, it is automatically passed and the AI moves again. If neither player has a valid move, the game ends and the player with more discs wins.
Can I play Reversi on my phone?
Yes! The game is fully optimized for mobile devices. The board scales to fit your screen, and you simply tap any highlighted cell to place a disc. No app download needed — just play in your browser.
Why are corners so important in Reversi?
Corners are the most powerful squares because once a disc is placed in a corner, it can never be outflanked or flipped. Corners also anchor entire edges and diagonals, allowing you to build stable groups of discs that your opponent cannot flip.
