Play Othello against the computer

Pick a strength and start. Beginner plays almost at random, Hard plays the last dozen moves perfectly. Undo is free and unlimited.

The short answer

Choose a difficulty, then click or tap any square with a dot on it. The computer replies in about a second. Black moves first, and you play black unless you change it. Everything runs in your browser, so your game never leaves your device.

Which level should you start on?

Most people should start on Easy. Beginner exists so you can learn the flipping rule without being punished, and it will still take a corner if you hand one over. Once you are winning on Easy without thinking, move up.

Beginner. Barely looks ahead, and it will walk straight past a free corner. Good for a first game or for showing someone how the discs flip.
Easy. Plays sensibly most of the time, then picks a second-best move often enough to give you a way back in.
Intermediate. Looks several moves ahead and plays the ending accurately. It will take corners and it will notice when you run out of moves.
Hard. Searches hard, then works out the end of the game outright. Once it says the position is solved, the result will not change no matter what you do.

Beside the board you can see how deep the computer looked, how many positions it checked and how long it took. When it has solved the ending it says so, and it tells you who wins with best play.

Beating the computer

The computer values corners, mobility and stable discs, in that order, so the way to beat it is to take those things away from it rather than to grab discs. Three things will get you further than anything else.

Do not touch b2, g2, b7 or g7 while the corner beside them is empty. These are the X-squares, and the computer will take the corner the move after you play one.
Count your legal moves. If you have three and the computer has twelve, you are already in trouble, whatever the disc count says.
Stay behind on discs until the last ten moves. Fewer discs early means fewer of your discs are sitting on the edge of the empty space where they can be flipped.

The strategy guide covers this properly, and X-squares and C-squares explains exactly why those four squares cost so much.

Saving a game to look at later

The move list beside the board fills in as you play, in standard a1 to h8 notation. Copy it and paste it back in another day to replay the game from the start, or press Copy link and send the position to someone else. If a pasted game has a move that cannot be played, the board tells you which move number is wrong instead of silently failing.

Prefer a human opponent?

Switch "Who is playing" to Two players and hand the device back and forth, or open the dedicated two player board. Same rules, same board, no computer.

Frequently asked questions

Is the computer opponent free?

Yes, all four levels, with no account and no limit on how many games you play. Undo is free too, which is not true of every Othello site.

How strong is the Hard level?

Hard searches for about a second per move, then solves the last twelve to fourteen squares exactly, so its endgame is perfect. It will punish an early X-square and it will take any corner you offer. It is not world-class, but it beats most casual players.

Can I play white against the computer?

Yes. Change "You play" to White and the computer opens as black. Black always moves first in Reversi, so as white you are answering rather than setting the shape of the game.

Why did the computer move twice in a row?

Because you had no legal move, so your turn was skipped. That is a normal part of Reversi, not a bug. The board says so when it happens. More on passing.

Does the computer cheat?

No. It sees the same board you do and follows the same rules. At Beginner and Easy it deliberately plays imperfectly so that a new player can win.

Can I take back a move against the computer?

Yes, as often as you like. Undo rewinds past the computer's reply to your own previous turn and restores every disc that was flipped.