AI OTHELLO
Options
Play Othello (Reversi) Online vs the Computer
Play the classic game of Othello — also known as Reversi — directly against the computer, free, in your browser, with no download and no sign-up. You play the black discs and move first; the AI plays white. Click one of the highlighted squares to place a disc and flip the white discs you trap. This is a single-player game built around an honest AI opponent: Beginner makes mistakes you can punish, Medium plays a solid positional game, and Hard runs an extremely strong search engine that thinks about a second per move. Legal moves are shown for you, the live disc count is always on screen, and your wins, losses and draws are tracked per difficulty.
How the AI thinks
The opponent here is shaped by a fact that makes Othello unlike most board games: disc count is almost meaningless until the very end — leading 30–4 at move 20 is usually a losing position. So the engine deliberately ignores the score it can see and searches for the position it wants. It generates the legal flipping moves, runs negamax with alpha-beta pruning, and evaluates on corner control, edge stability and mobility — how many moves it leaves you — rather than on material.
Curious how it decides? Watch minimax and alpha-beta run, step by step → Or see how much a deeper search is worth → Or read how the Othello AI works →
How to play Othello — the rules
- Start from the centre. The board opens with four discs in the middle, two black and two white on a diagonal. Black moves first.
- Flank to flip. Place a disc on a highlighted square so that it traps a straight line — horizontal, vertical or diagonal — of the opponent's discs between your new disc and another of your own. Every trapped disc flips to your colour.
- You must flip. A move is only legal if it flips at least one disc. If you have no legal move you pass, and the game tells you when that happens.
- Most discs wins. When neither side can move — usually when the board is full — the discs are counted and whoever has more wins. Equal counts are a draw.
- Hint and undo. Hint asks the engine for a strong move; Undo takes back your last move and the AI's reply.
Tips to beat the AI
- Take corners, avoid the squares next to them. A corner disc can never be flipped and anchors whole edges. But playing the square diagonally next to an empty corner (an "X-square") usually hands the corner to your opponent.
- Don't grab discs early. The player with fewer discs in the midgame often has more mobility and better moves. Flipping everything in sight early is a classic beginner trap.
- Limit your opponent's moves. Aim for positions where the AI has few legal moves — ideally forcing it to pass, which lets you play twice in a row.
- Think about the edges. Stable edge discs that can't be flipped are almost as valuable as corners; unstable edge discs can be turned against you.
Want to go deeper? Read our guide on how to analyze an Othello position with a free online analyzer — or the same for chess, checkers, backgammon, and mancala.
FAQ
Can I play Othello online against the computer?
Yes — this page is Othello (Reversi) played directly against the computer in your browser. There is nothing to download and no account to create: pick a difficulty, choose whether you or the AI moves first, and click one of the highlighted squares to place a disc. It works on desktop and mobile.
What is the difference between Othello and Reversi?
Othello and Reversi are essentially the same game. Reversi is the older 19th-century game; Othello is the standardised modern version, which always starts with the four central discs placed in the same fixed diagonal pattern and Black moving first. This page uses the standard Othello rules, and the two names are used interchangeably.
How strong is the Othello AI?
The Othello AI's strength depends on the level. Beginner deliberately plays some random moves, so it gives away corners and edges. Medium plays a solid positional game. Hard runs a negamax search engine with alpha-beta pruning that values corners and mobility, thinking about a second per move and reading the exact result near the end of the game. It is extremely strong, though we do not claim it plays perfectly.
What are the rules of Othello?
Othello's rules start with four discs in the centre of the board. On your turn you place a disc on an empty square so that it traps one or more of the opponent's discs in a straight line — horizontally, vertically or diagonally — between the new disc and another of your own; every trapped disc then flips to your colour. You must play a flipping move if one is available; if you have none you pass. When neither player can move the game ends, and whoever has more discs on the board wins.
What happens if I cannot move in Othello?
If you have no legal flanking move you must pass and it becomes your opponent's turn; the game tells you when this happens. If neither player has a legal move — which usually means the board is full — the game is over and the discs are counted. Passing is part of the strategy: sometimes forcing your opponent to pass hands you two moves in a row.
Is AI Othello free, and does it work offline?
AI Othello is completely free with no download and no sign-up. The game and the AI engine run entirely client-side in your browser, so once the page has loaded it keeps working even without a connection. Your win/loss record is stored locally in your browser. More AI games: AI Chess, AI Checkers, AI Connect 4, AI Tic Tac Toe or AI Sudoku.
More AI games on LK Forge
You win!
You finished with more discs.