Backgammon: the full rules against an AI that actually defends

01  What it is

Backgammon is a race. You and your opponent each start with fifteen checkers on a board of twenty-four points, moving in opposite directions, and the first player to bring all fifteen home and bear them off wins. The dice make it a game of risk rather than of perfect information: every roll offers you a set of choices, and most of them are wrong in a way you only notice four rolls later.

This is a browser version of that game, played against the computer. You pick one of four difficulty levels, and a single game starts immediately. There is no account, no sign-up, no download and nothing to install — open the page and the board is there. It is free and supported by ads, and it is for entertainment only: there is no betting, no stakes and no real-money play anywhere in it.

The whole game is built for a phone first. Rather than shrinking a desktop board, the tap zones are the full point columns, so a checker is a comfortable target even on a 360-pixel screen. Tap a checker and the points it can legally reach light up; tap one of those and it moves. Everything else — the dice, the opponent, the result card — is computed in your browser, and no game server ever sees your moves.

02  How a game runs, in the order it happens

The game opens the way a real one does. Each side rolls a single die, and the higher roll starts and plays both of those numbers as its first turn — so a 6–3 opener plays as a 6 and a 3, not as a single move. Ties are re-rolled until someone leads.

From then on a turn is two dice, and each die is a separate move: a 5 and a 3 lets you move one checker five points and another three, or move a single checker eight points in two hops, as long as both landings are legal. You must use both numbers if there is any legal way to do it, and if only one can be played you must play the higher. Doubles are the exception to all of this — roll two 4s and you play four moves of four, not two.

A point is open to you if it is empty, if it holds your own checkers, or if it holds exactly one enemy checker. Two or more enemy checkers block it. Land on that lone enemy checker and it is hit, and it goes to the bar — where its owner must re-enter it on the far side of the board before making any other move. Getting hit at the wrong moment can cost you a whole game, which is why leaving single checkers exposed is the mistake beginners make most.

Once all fifteen of your checkers are in your home board, you start bearing them off. A die removes a checker that many points from the edge; if the exact point is empty you can bear off from a lower one, provided nothing of yours sits higher. Clear all fifteen and the game is over.

The margin matters too, because backgammon scores by how badly you won. If your opponent has borne off nothing at all, the win is a gammon — a double. If they have borne off nothing and still have a checker on the bar or trapped in your home board, it is a backgammon — a triple. You will see which one you got on the result screen.

Nothing here is irreversible while it is your turn: an undo button steps your last move back, so a mis-tap costs you a second rather than the game.

03  Four levels, and what actually changes between them

All four levels run the same rules engine and the same dice. What differs is how the computer decides which turn to play, and the difference is real rather than cosmetic.

Beginner does not evaluate the position at all in any meaningful sense. It ranks every legal turn by pip race alone and then picks at random among the three best, which means it drives its checkers forward and happily leaves single checkers sitting where you can hit them. It is a warm-up, not an opponent.

Casual uses the full evaluation. That scoring function weighs the pip race, how many of the thirty-six dice rolls could hit each of its exposed checkers, the points it has made and the primes it has built, the anchors it holds in your home board, how strong its home board is while you are stuck on the bar, and how cleanly it can bear off. It covers its blots and makes points, and it will punish careless play.

Sharp takes the three turns that evaluation likes best and then does something the lower levels never do: for each candidate it plays out your best reply to all thirty-six possible rolls and averages the result. It is choosing the move that holds up after you have answered it, not the move that looks best right now. It is a genuinely tough game, and loose play gets punished.

Expert is the same idea with a wider net — it re-examines five candidates rather than three, and it defends harder on every safety measure, valuing blot cover, primes, anchors and home-board pressure more heavily than Sharp does.

How strong is that, honestly? In this codebase's own test suite — which I ran, thirty tests, all passing — each level plays two hundred seeded games against an opponent that moves at random, alternating colours so neither side gets the first roll for free. Beginner wins more than half of them, Casual at least 70%, Sharp at least 85%. Treat that as a floor and not a rating: a random mover is a very weak baseline, and none of these levels is a neural-network engine. They are club-level heuristics with a shallow look-ahead, which is to say beatable, and satisfying to beat.

04  Pips, the result card and the streak

Both sides start a game at 167 pips — the total distance their fifteen checkers have left to travel. The number is on screen for both players throughout, and reading it is the single most useful habit in backgammon: the lower count is ahead in the race, and the size of the gap tells you how much risk you can afford. Twenty pips ahead with contact broken, and you should stop worrying about being hit. Twenty behind with the opponent holding your anchor, and you cannot win a pure race — you have to play for a shot.

At the end of a game you get a result card: a 1080×1920 image showing how you won, the pip margin you won by, how many moves the game took, the difficulty you played and your current streak. It is drawn on your device from the game's own numbers — there is no text box anywhere in the game, so nothing you could type ever ends up on it. You can share it through your phone's normal share sheet, copy it, or download it.

The streak is the reason to play one more. It is a single number kept in your browser, and it goes up when you beat the AI and back to zero when the AI beats you. It will still be there tomorrow on the same device, and it never leaves your browser — which also means it does not follow you to a different phone, and clearing your browsing data clears it. The only other thing stored on your device is your mute preference.

05  What it deliberately leaves out

It is worth being plain about the scope, because backgammon has a long list of conventions and this game does not include all of them.

There is no doubling cube. The cube is the standard way two players raise the stakes of a game, and it is a genuinely interesting part of serious backgammon — but here it is absent, along with anything else that would imply stakes. What you get instead is the gammon and backgammon scoring, which is where the extra value in a well-played game actually comes from.

There is also no match play to a points total, no online multiplayer or pass-and-play, no accounts, no stored history and no move analysis or equity engine. It is one player against one AI, one game at a time, with a rematch button. That is a deliberate limit rather than an oversight: the whole thing is a single page that runs on your device, and everything it does not have is something it does not need a server for.

06  Six habits that move your win rate

Backgammon rewards a handful of disciplines far more than it rewards clever individual moves, and this AI is built to punish players who skip them.

• Count the shots before you leave a blot. A single checker six pips from an enemy checker is a different risk from one that needs a specific combination, and Casual and above are literally scoring that count.
• Make points rather than chasing pips. Two checkers on a point are safe and block the opponent; a lone checker is a target. Against Sharp and Expert, the exposed single is what loses you the game.
• Build a prime. Several made points in a row are close to impassable, and a checker trapped behind one may sit there for the rest of the game.
• Hold an anchor when you are behind. A made point deep in the opponent's home board gives you somewhere safe to land and a chance to hit them late, which is often the only route back into a lost race.
• Once contact is broken, stop playing safe and run. In a pure race there is nothing left to be hit by, and the most pips forward each roll is the only thing that matters.
• Bear off without gaps. Keep your low points filled and avoid leaving holes that waste a roll — the endgame is where a close race is decided, and a wasted pip there is fatal.

07  Questions people ask

Is this backgammon free, and do I need an account?

It is free, and there is no account, no sign-up and no login. The game is supported by ads and runs entirely in your browser. Nothing is installed.

Can I play backgammon against the computer on my phone?

Yes — the board is designed for portrait phones first, and the tap zones are full point columns so checkers are easy to hit on a small screen. Tap a checker, then tap a highlighted destination. It works on desktop too.

What is the difference between a gammon and a backgammon?

Both are ways of winning by more than a single game. If your opponent has borne off none of their checkers when you finish, it is a gammon — a double win. If they have borne off none and still have a checker on the bar or trapped in your home board, it is a backgammon — a triple win.

Does this game have a doubling cube?

No. There is no doubling cube and no match play to a points total — it is a single game against the AI, with the gammon and backgammon bonuses as the scoring. That also keeps the game free of anything resembling wagering.

How strong is the AI, and which level should I start on?

Start on Beginner or Casual. Casual uses a full position evaluation and covers its checkers; Sharp and Expert additionally play out your best reply to all thirty-six rolls before choosing, and Expert examines more candidates and defends harder. In the game's own test suite, over two hundred seeded games each against a random-moving opponent, Casual wins at least 70% and Sharp at least 85% — but a random mover is a weak baseline, so treat that as a floor rather than a rating.

Is backgammon gambling? Is there any real money involved?

Not here. This is a for-fun game with no wagering, no stakes and no real-money play of any kind, and there is no way to put anything on the line. It is played purely for the result and the streak.

08  More from the shelf

• Tilewright — Draw seven tiles. Outword the AI.
• Chess — Beat the engine. Post the win.
• Dominoes — Match the ends. Block them out.
• Fiveaside — Score past the keeper. Post the scoreline.

Browse every app in the catalogue →