Play Reversi Online

The classic disc-flipping strategy game — also known as Othello. Place your discs to outflank and flip your opponent's pieces. Challenge the AI or play with a friend.

Game Mode
AI Difficulty
You: 2
vs
AI: 2
Your turn — place a black disc

What Is Reversi?

Reversi is a classic two-player strategy board game played on an 8×8 grid with double-sided discs — black on one side, white on the other. Players take turns placing a disc of their colour on the board. When you sandwich one or more of your opponent's discs between your new disc and another disc of your colour (horizontally, vertically, or diagonally), those opponent discs are flipped to your colour.

When neither player can make a legal move the game ends, and the player with the most discs on the board wins. Reversi is also widely known as Othello — a trademarked version introduced in 1971 by Goro Hasegawa in Japan. The original Reversi rules were invented in the 1880s by Lewis Waterman and John W. Mollett in England. Despite the different names, the gameplay is identical.

How to Play Reversi

  1. Starting position. The game begins with four discs in the centre of the board — two black and two white, placed diagonally.
  2. Place a disc. On your turn, tap or click a valid cell. A move is valid only if it outflanks (sandwiches) at least one of your opponent's discs in an unbroken line.
  3. Flip discs. All outflanked opponent discs in every direction are immediately flipped to your colour.
  4. Pass if stuck. If you have no legal moves, your turn is automatically passed. If neither player can move, the game ends.
  5. Win! When the game ends, the player with the most discs on the board wins. If both have 32, it's a draw.

Reversi Strategy Tips

1. Secure the Corners

The four corner squares are the most valuable positions on the board because corner discs can never be flipped. Once you own a corner, you can use it as an anchor to build a wall of stable discs along the edges. Getting corners early gives you a massive strategic advantage.

2. Avoid the X-Squares and C-Squares

The squares diagonally adjacent to a corner (called X-squares) and the squares directly adjacent to a corner along the edge (called C-squares) are dangerous to occupy when the adjacent corner is empty. Playing there often gives your opponent the corner. Avoid these cells in the early and mid-game unless the corner is already taken.

3. Play for Mobility, Not Disc Count

Beginners often try to flip as many discs as possible on every turn. This is usually a mistake. Having fewer discs in the early game can actually be advantageous — it limits the number of legal moves your opponent has (since they need your discs to outflank). Focus on mobility: maximising your own legal moves while minimising your opponent's.

4. Build Stable Edges

Discs along the edges that connect to a corner of your colour are stable — they can't be flipped. Once you control a corner, expand along both edges leading away from it. A fully stable edge is worth far more than a large cluster of discs in the centre that can be flipped later.

5. Control the Centre Early

In the opening, try to keep your discs centralised. Spreading to the edges too early (without corners) gives your opponent outflanking opportunities from multiple directions. Stay compact, keep your options open, and wait for the right moment to expand.

6. Plan for the Endgame

The last few moves of a Reversi game can swing the score dramatically. As the board fills up, forced sequences become predictable — so think ahead. Count empty squares, anticipate which moves will be forced, and try to set up sequences where you play last in key regions.

About the AI

The AI uses the minimax algorithm with alpha-beta pruning and a positional evaluation function tuned for Reversi. Here's how each level plays:

  • Easy: Looks 2 moves ahead and sometimes picks random moves. Great for learning the rules and basic strategy.
  • Medium: Looks 4 moves ahead with evaluation based on corner control, edge stability, mobility, and disc count. A solid challenge for intermediate players.
  • Hard: Looks 6 moves ahead (deeper in the endgame) with advanced evaluation weighing corner control, stability analysis, frontier minimisation, and mobility. Very tough to beat — can you find a way?

History of Reversi

The origins of Reversi are somewhat disputed. The game was likely invented around 1883 in England, with both Lewis Waterman and John W. Mollett claiming credit. The rules were published in The Saturday Review and the game quickly became popular in Victorian-era Britain.

In 1971, Japanese game enthusiast Goro Hasegawa introduced the game under the trademarked name Othello, adding the fixed starting position (four discs in the centre). Othello became a worldwide phenomenon and has been the subject of formal competitive play ever since, with an annual World Othello Championship held since 1977.

Reversi is also a popular subject in computer science and AI research. It was one of the first board games where computer programs could consistently beat top human players — notable milestones include the program Logistello, which defeated the reigning world champion Takeshi Murakami 6–0 in 1997.

Frequently Asked Questions

Reversi is a two-player strategy board game played on an 8×8 grid. Players take turns placing discs on the board. When you place a disc that sandwiches one or more of your opponent's discs in a straight line (horizontally, vertically, or diagonally), those discs are flipped to your colour. The player with the most discs when the board is full — or neither player can move — wins.
Reversi and Othello use the same rules and board. Othello is a trademarked version of the game introduced in 1971 by Goro Hasegawa. The original Reversi concept dates back to the 1880s. In practice, the gameplay is identical — the terms are used interchangeably.
The key strategies are: secure the four corners (they can never be flipped), avoid giving your opponent corner access by staying away from the squares next to empty corners, keep your disc count low in the early game to limit your opponent's options, and control the edges once you have corners.
Yes! This Reversi game is fully responsive and designed for mobile-first play. Tap any valid cell to place your disc, with visual indicators showing all legal moves.
There are three levels: Easy (makes reasonable but sometimes random moves, great for learning), Medium (uses minimax search with positional evaluation — a solid challenge), and Hard (deep search with advanced corner, edge, mobility, and stability analysis — very tough to beat).

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