Play Othello (Reversi) Online Free

Othello's entire rule set fits in a single sentence - place a disc so that it sandwiches a line of enemy discs between two of yours, and flip everything you trapped. From that sentence comes a game famous for brutal swings: a board that looks 90 percent yours at move 40 can finish 40–24 against you, because the last moves flip the most.

That is the hook. Where most games reward accumulating, Othello rewards positioning. Discs are not points, they are ammunition - and the player who controls where the final flips happen usually wins regardless of what the count said an hour of moves earlier.

Select “vs Computer” to take Black (the first player) against the engine, or “2 Players” to alternate on one device. Difficulty pills switch the computer between random, greedy and positionally-aware play.

• Your legal squares are marked with subtle gold dots - tap one to place your disc.
• Every bracketed line flips at once; the animation is quick and the live disc count in the status bar updates immediately.
• If a player has no legal move, the turn passes automatically with an announcement - you never need to work out whether a pass is due.
• The last move is outlined in gold so a returning glance tells you what just happened.

The game ends when neither colour can move or the board fills, and the final count decides everything.

Black moves first from the standard four-disc centre (black on d5 and e4, white on e5 and d4 in algebraic terms). A move must bracket at least one straight line of opponent discs - horizontal, vertical or diagonal - between the newly placed disc and an existing disc of your colour. All bracketed discs in all directions flip simultaneously.

The details that trip up new players:

• You may only place a disc on an empty square, and only if the placement flips something - quiet moves that flip nothing are illegal.
• Flipping is compulsory and complete: you cannot choose to flip only part of a line.
• If you have no legal move, your turn is skipped. There is no choice to pass when you do have a move.
• The game ends when both players are out of moves (usually because the board is full). Most discs wins; 32–32 is a draw; a 64–0 finish is announced as a perfect game.

Four squares can never be flipped: the corners. A disc in a corner is permanent territory, which makes corners the most valuable squares on the board by a wide margin. Everything else in Othello strategy flows from that fact.

• Never feed the corners: the squares directly next to a corner become traps the moment the corner is empty. The diagonal neighbours (the X-squares) are the worst - playing there early is close to donating the corner.
• Edge discs are stable-ish: once an edge fills with no gaps, those discs stop being flippable. Building sealed edges is a quiet, compounding advantage.
• Count mobility, not discs. Having few legal moves (even with a big disc count) means the opponent dictates play; keep your options open and starve theirs.
• Play for the evens and odds of the endgame: when few empty squares remain, forcing your opponent to fill the square before a corner decides games.

The Hard computer here uses corner-weighted evaluation two moves deep, so it will visibly refuse X-square bait - study which squares it declines.

Chasing the disc count is the classic error. Beginners flip greedily through the opening, ending up with a fat majority of flippable, unstable discs and no moves left, while the opponent holds a thin line of quiet discs and takes the whole board at the end.

The second habit to break is fearing lost material. In Othello losing discs is often free - the fewer discs you have, the fewer targets your opponent can flip, and the longer your mobility lasts. Treat the scoreboard as noise until roughly the last ten moves, then start counting for real.

The rules engine validates every placement against full eight-direction bracketing, so illegal squares simply never register. Passes are detected and announced automatically, the final count is exact, and the session score carries across rematches.

The computer's three levels represent genuinely different philosophies: Easy plays uniformly at random, Medium always grabs the largest immediate flip, and Hard runs a two-ply minimax with the classic positional weight table - corners prized at full value, X-squares penalised, edges credited. Nothing leaves your device at any point, and a full game runs in a couple of minutes - the speed most Othello is actually played at.