At a glance
| What matters | Boardgammon | Typical mobile backgammon apps | Desktop analyzers (GNU Backgammon, eXtreme Gammon) |
|---|---|---|---|
| Can you check the dice? | Yes. Each online roll is committed with a SHA-256 hash before it is shown, and every online game has a public audit page. | Usually not. The dice come from a generator you cannot inspect, so fairness is a promise. | Not their job: they analyse games, and the dice of a game played elsewhere are whatever that site rolled. |
| Analysis after the game | Every finished online game is analysed by GNU Backgammon on our servers. Your PR and error counts are free; the move-by-move review is Pro. | Often none. Where it exists, it is commonly limited or sold separately. | The deepest there is: full analysis and rollouts. You export each match from where you played and import it. |
| Ads | None in the browser. The free mobile app has one small banner on the offline variants screen, and videos only when you tap for a reward. Never during a game. Pro has none. | Ads between games are common in free apps. | None. |
| What you have to buy | Nothing. Rated online play, the dice audit, every variant, the Easy and Medium computer opponents and your PR are free. Pro, themes and coin packs are optional. | Many are built around coin stakes, with frequent offers to buy more. | GNU Backgammon is free and open source; eXtreme Gammon is commercial software. |
| Where you play | In your browser at boardgammon.com/play, and in the iPhone and Android apps, on one account. | A phone app, sometimes with a web version. | A computer, against the engine or for analysis. |
“Typical” means what is common in free backgammon apps, not any one app; some do better on one row or another. If yours does, keep it.
Dice you can audit, roll by roll
A dice generator you cannot see is a promise. A commitment is something you can check, and on Boardgammon every roll of an online game carries one:
Committed before it is shown
For each roll the server draws a fresh secret seed and publishes its SHA-256 hash first. The hash fixes the seed without revealing it, so the seed cannot be swapped afterwards.
A second number goes in
In a live game your device sends a random number of its own. The dice are computed from both numbers with HMAC-SHA256, together with the game’s ID, the roll’s ID and a counter, and every face is equally likely. Nothing about the position, the score or the players is an input.
Revealed with the roll
The seed is shown with the dice, and each online game has a public audit page at
api.boardgammon.com/audit/<game-id>listing every roll’s commitment, seed and dice, with a short program you can run to recompute them.
What the record does not show, we say plainly: when the server supplies the second number too, as in a correspondence game, the record still shows the roll was not changed after it was recorded, but it cannot show the server did not know the roll in advance. The full method is on the fair dice page, and the server checks every move against the rules as well.
Analysis you don’t pay for
Every finished online game on Boardgammon is analysed by GNU Backgammon, the open-source engine many strong players train with, running on our servers. You don’t export a file or open a desktop program: after the game, your PR, your performance rating, comes back with your error counts. That summary is free on every account. Pro adds the move-by-move review, with the engine’s best play and the equity each decision cost, and rollouts on demand.
The same engine produced the numbers in our strategy guides. Each of the 15 opening rolls has its own page with GNU Backgammon rollouts of the top candidate plays, such as 3-1 or 6-4, and the skill-levels guide explains what your PR says about your game.
No ad breaks, no forced packs
In the browser there are no ads at all. The free iPhone and Android apps show one small banner, below the list on the offline variants screen, and play a video only when you tap to watch one for a reward, such as a hint or coins. After a few games against the computer the app may offer such a video before the next one; “No thanks” starts your game straight away. No ad ever interrupts a game, and Pro removes them all.
Nothing has to be bought. Rated online play, the dice audit, all nine backgammon variants, the Easy and Medium computer opponents, lessons and your per-game PR are free. Pro, premium board themes and coin packs are there for players who want them; Pro deepens the analysis and never buys dice.
If you already use a desktop analyzer
Keep it. GNU Backgammon and eXtreme Gammon are the deepest tools in the game, and Boardgammon runs GNU Backgammon itself. What we add is the step before: a table where the dice can be audited, and analysis that arrives on its own after each online game, so the review habit costs nothing to start.
New to the words? The glossary has a page for each of its 101 terms, from anchor to provably fair dice.