How to play backgammon

Each player has 15 checkers. You move yours around the board toward your home board, then take them off the board, which is called bearing off. The first player to bear off all 15 wins.

The board has 24 narrow triangles called points, in four quarters of six. Your home board is the quarter where your checkers finish. The bar down the middle separates the two halves.

Each side starts with 2 checkers on its 24-point, 5 on its 13-point (the midpoint), 3 on its 8-point and 5 on its 6-point. Your opponent's checkers mirror yours, moving the other way.

Set up the board step by step

Each player rolls one die. The higher number moves first and plays the two numbers just rolled. On a tie, both roll again. After that, players take turns rolling both dice.

The two dice are two separate moves. Move one checker by one die and another checker by the other, or one checker by both, as long as the point where it stops in between is open.

A point is open unless two or more of your opponent's checkers are on it. You can land on an empty point, on your own checkers, or on a single opposing checker.

• Doubles are played twice: a roll of 4-4 gives four moves of 4.
• You must use both dice whenever you can. If only one of them can be played, play it; if either one can but not both, play the higher one.
• If no move is possible, your turn passes. Checkers never move backwards.

A single checker alone on a point is called a blot. Land on your opponent's blot and you hit it: it goes to the bar in the middle of the board.

A player with a checker on the bar must bring it back in before moving anything else, entering on the opponent's home board at the point that matches one of the dice. If both of those points are blocked, the whole turn is lost.

Once all 15 of your checkers are in your home board, you start bearing off: a 6 removes a checker from the 6-point, a 4 from the 4-point, and so on. You may also move a checker inside your home board instead.

• If no checker sits on the point a die shows, you must move a checker from a higher point. With nothing higher either, bear off from your highest point.
• If one of your checkers is hit while you are bearing off, it must come all the way around again before you continue.

A game starts worth one point. The large die marked 2, 4, 8, 16, 32 and 64 is the doubling cube. Before rolling, a player who feels ahead can offer to double the stakes. The opponent then decides:

• Take: the game goes on at double the value, and the player who took now owns the cube. Only the owner can offer the next double.
• Pass: the game ends at once, and the player who passed loses its value before the double.

Knowing when to double, take and pass wins more points than good checker play alone. On Tavlino, matches to 3, 5 and 7 use the cube, and you can switch it off against the AI.

How much a game is worth depends on how far behind the loser is when the winner bears off the last checker.

• 1xSingle gameThe loser has borne off at least one checker.
• 2xGammonThe loser has not borne off a single checker.
• 3xBackgammonThe loser has borne off nothing and still has a checker on the bar or in the winner's home board.

That multiplier applies to the value of the doubling cube: a gammon with the cube on 4 is worth 8 points.

A match is played to a number of points, such as 3, 5 or 7. Games continue until one player reaches that total.

Without it, the trailing player would double at once in every game, because they would have nothing to lose.

Online, every roll comes from our server, never from either player's device, and anyone can check afterwards that the server did not choose the dice. It works in three steps:

1. 1Sealed before the first rollThe server picks a secret seed and publishes its fingerprint (a SHA-256 commitment) before the match starts. It cannot change the seed later without the fingerprint changing.
2. 2Both players add their own seedEach player's device sends a random seed of its own. Every roll is computed from all three seeds and the roll number, so the server alone cannot aim a roll.
3. 3Revealed after the matchWhen the match ends, the secret seed is revealed. The Verify page recomputes every roll in your browser and shows whether it matches the game.

Every finished online match has a Verify link next to its replay.