Backgammon and Long Nardy Online
An online board for backgammon and long nardy: play free and without signing up against a computer at four levels, with a second person on the same screen, or with a friend by link. The rules are the official ones, from the head rule to mars, and after the game a neural network shows where the mistakes were and how lucky the dice were.
How to play
Long nardy or backgammon; the computer, a second person on this screen, or a friend by link.
Press Roll or tap the board. The opening roll decides who starts.
Tap a checker, then a highlighted point — or drag it there. Done (or a tap on the dice) passes the turn.
Bear off all 15 checkers first, then open the review: mistakes move by move and luck with the dice.
Play the computer, a second player or a friend by link — no sign-up
What the board can do
Rules of backgammon and long nardy
Long nardy
- Set-up and direction
- Each player has 15 checkers stacked on one point — the head. The heads sit on opposite sides of the board, and both players move the same way round it. Your home is the last quarter of your path.
- No hitting
- A point with even one opponent checker is closed to you. Checkers are never hit, so the game is about blocking the way.
- The head
- Only one checker may leave the head per turn. The one exception is a player's first roll of 6-6, 4-4 or 3-3: then two leave, because a single checker would run into the opponent's head.
- The six-point block
- You may hold six points in a row only if at least one opponent checker is already past them. Building such a block is not allowed even for a moment within your turn.
- Using the dice
- Each die is a separate move; a double is played four times. If both dice can be played, both must be. If only one can, and either could, play the larger.
- Bearing off and scoring
- Once all 15 are home, bear them off by the exact number, or by a higher number from the highest point. First to bear off all wins: oin 1 point, mars 2 when the loser bore off none.
Backgammon (short nardy)
- Set-up and direction
- Each side has two checkers on its 24-point, five on the 13, three on the 8 and five on the 6. The players move in opposite directions towards their own homes.
- Hitting and the bar
- A lone checker (a blot) is hit when an opponent lands on it and goes to the bar. Two or more checkers close a point.
- Entering
- A checker on the bar must enter the opponent's home before any other checker moves. If both entry points are closed, the turn is lost.
- Using the dice
- Both dice must be played when possible, the larger one if only one can be; a double is played four times.
- Bearing off
- With all 15 at home, bear off by the exact number or by a higher number from the highest point. A hit checker must come home again before bearing off continues.
- Scoring and the cube
- A win is 1 point, a mars (gammon) 2 when the loser bore off none, a koks (backgammon) 3 if they still have a checker on the bar or in the winner's home. The doubling cube doubles the stake; the Crawford rule removes it for one game at match point.
Based on the Russian Ministry of Sport rules for nardy (2024) and the standard rules of backgammon.
The short-game neural network is the open wildbg engine by Carsten Wenderdel (github.com/carsten-wenderdel/wildbg, CC0); the long-nardy network was trained by us on these rules.
Why this board is a good place to learn
Most arguments over a backgammon board are about the rules: may two checkers leave the head now, is this block allowed, why is the four not playable. Here every move is checked against the official rules, the points you can reach are highlighted, and a tap on a forbidden point names the rule. After the game the review shows which moves cost points, and dice you can verify settle the question of whether they are rigged. A game against the computer or a friend becomes practice, not an argument.
Questions about backgammon and long nardy
What is the difference between long nardy and backgammon?
In long nardy all 15 checkers start on one point, both players move the same way round the board and nothing is hit: a single checker already closes a point, so the game is about blocking. In backgammon (short nardy) the checkers start spread out, the players move towards each other, a lone checker can be hit to the bar and has to enter again. Scoring differs too: long nardy pays 1 or 2 points, backgammon up to 3.
How can I check that the dice are not rigged?
Before the first roll the board picks a secret number and shows its SHA-256 fingerprint in the Dice tab. Every roll of the series is computed from that number and the roll's index, so a die cannot be changed once the fingerprint is shown. Press «Reveal the number and check the rolls» — the number appears and all rolls are recomputed; any SHA-256 calculator gives the same result. In a game by link every roll is built from both players' random numbers.
How strong is the computer?
Easy plays a random legal move, Medium weighs pips, blots and blocks. Strong and Master play with a neural network: in backgammon it is the net of the open wildbg engine, which its author measured at the level of a strong player; in long nardy it is our own, trained on hundreds of thousands of games against itself. In our tests Strong beats the previous algorithm in two games out of three at backgammon and five out of six at long nardy, and Master also works through the other side's replies to all 21 rolls and beats Strong in 53 games out of 100 at backgammon and 56 at long nardy (2,000 games each).
What does the game review show?
After the game the neural network goes through every move: how many points of a game it gave up against the best move, and it marks inaccuracies, mistakes and blunders. For each side it counts accuracy, PR — the mean error per move, the scale backgammon players know — and luck: how much better or worse the rolls were than average. Tap a move in the list and the board shows the position before it, with the move as arrows.
Why can two checkers leave the head only on 6-6, 4-4 and 3-3?
From the head a single checker can play 1-1, 2-2 and 5-5 in full, but with 6-6, 4-4 and 3-3 it runs into the opponent's head after one, two or three steps, and the rest of the roll would be lost. That is why the rules let two checkers leave the head on a player's first roll of these doubles. Under the official start the first mover plays the two single dice of the opening roll, which are never a double, so the exception meets only the second player; the board applies it to both, which gives the same result.
Why does the board not let me close a sixth point in a row?
In long nardy a block of six consecutive points is allowed only while at least one opponent checker is already past it; otherwise all 15 of their checkers would be locked. The rule counts points along the opponent's path and applies even for a moment inside your turn, so a step that would complete such a block is refused even if the next step would open it again.
What are oin, mars and koks?
Oin is an ordinary win for 1 point: the loser managed to bear off at least one checker. Mars is 2 points: the loser bore off none. Koks (a backgammon) is 3 points in the short game, when the loser bore off none and still has a checker on the bar or in the winner's home. The official rules do not use koks in long nardy; some families do, so the board offers it as an option.
Why must I play a certain die when both look possible?
The rules require using both dice whenever that is possible. If one order of moves would leave the second die unplayable while another order plays both, only the second is allowed. And when only one die can be played in any way, it has to be the larger one. The board applies both rules and names them when it refuses a move.
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