Play Backgammon Online vs the Computer

Play backgammon — the classic dice-and-checkers race game — directly against the computer, free, in your browser, with no download and no sign-up. You play the white checkers by default and move first; the AI plays black. Press Roll Dice, then click one of your checkers and the highlighted point you want to move it to. This is a single-player game built around an honest AI opponent: Beginner plays loose moves you can punish, Medium plays a solid game, and Hard runs a two-ply expectiminimax engine that averages over the dice. Legal moves are highlighted, both pip counts are always on screen, and your wins and losses are tracked per difficulty.

How the AI thinks

Backgammon is not a perfect-information game like chess or Othello — the dice make it a game of chance as well as skill — so the opponent here cannot use plain minimax. Instead it uses expectiminimax, the classic algorithm for games with randomness: alongside the usual move nodes it adds chance nodes that average an evaluation over all 21 distinct dice rolls, each weighted by how likely it is (a double is half as likely as a mixed roll). On its turn the engine first generates every legal way to play the two numbers it rolled — respecting the rules that you must use as many dice as you can, and the larger die if only one will go — and at the Hard level it looks a move further, weighing your most likely replies across the whole dice distribution. Each position is scored on the things that actually win backgammon games: the pip count (who is ahead in the race), checkers already borne off, made points and primes that block the opponent, and the risk of leaving a blot that can be hit. The whole engine runs locally in your browser, in a background worker thread so the page stays responsive, and nothing is sent to a server. It is a strong, honest opponent, though we do not claim it plays perfectly.

Curious how game-tree search works? Watch minimax and alpha-beta run, step by step → Or read how the Backgammon AI works →

How to play backgammon — the rules

• The race. Each side has fifteen checkers and moves them in opposite directions around the 24 points, toward its own home board, then bears them off. First to bear off all fifteen wins.
• Use both dice. The two dice are two separate moves; you may play them with one checker or two. Roll a double and you play that number four times. You must use as many dice as legally possible.
• Making points and hitting. You cannot land on a point holding two or more enemy checkers. Landing on a lone enemy checker — a blot — hits it and sends it to the bar.
• The bar. A checker on the bar must re-enter in the opponent's home board before you make any other move. If you cannot enter, you forfeit the roll.
• Bearing off. Once all fifteen of your checkers are home, each die bears a checker off the matching point; a number higher than your highest point bears off from that point.
• Hint and undo. Hint asks the engine for a strong move; Undo takes back your checker moves within the current roll.

Tips to beat the AI

• Make your points. Two checkers on a point build a wall. Six points in a row is a prime the opponent cannot jump — a made board wins races and contains hits.
• Watch your blots. A lone checker in range of enemy checkers can be hit and sent all the way back. Cover blots or leave them where the fewest numbers hit them.
• Hit when it gains ground. Sending an enemy checker to the bar costs it pips and time — especially when you have a strong home board it must enter against.
• Know when it's a race. Once the checkers have passed each other there are no more hits: count the pips and just run. When contact remains, safety matters more.

Want to go deeper? Read our guide on how to analyze a backgammon position with a free online analyzer — or the same for chess, checkers, Othello, and mancala.

FAQ

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