Fair dice you can check

Last updated 28 October 2026

Ask players about backgammon apps and you soon hear that the dice are rigged. In Backgammon Room you don’t have to take our word for it: every game’s dice are locked before the first roll, every roll can be checked after the last one, and you can roll real dice instead.

Why dice feel rigged

Backgammon is a game of skill played with a lot of luck, and the rolls we remember are the ones that hurt. A few numbers help:

A double comes 1 roll in 6, and two doubles in a row 1 time in 36: over an evening of games, you’ll see it more than once.
A checker left alone 6 points in front of an opponent’s checker is hit by 17 rolls out of 36, nearly half the time, when nothing stands in the way. From 1 point away, 11 rolls hit it; from 7 points away, only 6.
When five points of a home board are closed, a checker on the bar comes in with 11 rolls out of 36: it stays out more than two times in three.

So the roll that “always” comes against you usually had a fair chance of coming. That’s also why each game’s review shows how lucky the dice were next to your mistakes: you see how much of a result came from the dice, and how much from the play.

How often would fair dice do that?

A streak feels impossible when it happens to you, but over many rolls fair dice make long streaks all the time. Ten rolls without a double, for example, come about 1 time in 6 on any ten rolls, and almost surely somewhere in an evening of play.

Some examples. A game here is 20 of your rolls, about what each player rolls in a game with the doubling cube, so 100 rolls are about five games.

What happened	On the next rolls	Somewhere in one game	Somewhere in 100 rolls
No double for 10 rolls in a row	16%1 time in 6.2	43%	98%
No 6 for 6 rolls in a row (or any one number you need)	11%1 time in 8.9	53%	99%
A double twice in a row	3%1 time in 36	38%	91%
6-6 twice in a row (or any one double)	less than 0.1%1 time in 1,296	1%	7%
Stuck on the bar 3 turns in a row against five closed points	33%1 time in 3	–	–

Being stuck on the bar counts only the turns you’re on the bar, so it has no figure per game. Every other chance in backgammon, from hitting to bearing off, is in backgammon dice odds.

Against the bots: locked before move 1

Before the first roll, your iPhone picks a secret key at random and shows its fingerprint, the lock: “Dice locked before move 1”, in Game info (tap ⓘ during a game).
Every roll of the game is worked out from that key and the roll’s number, so no roll can change once the game has started, whatever you play and whatever the bot’s level. The bot only ever sees the roll in front of it.
When the game ends, Game info shows the key itself. Anyone can check it against the lock and work out every roll again.

Every bot, from Mia to The Cube, plays with the same fair dice. Only its thinking changes. There are no easier dice for new players and no “comeback” dice for whoever is behind.

Online: three secrets, checked at the end

Before the first roll, our server picks a secret number and shows your app its fingerprint. It can’t change the number after that.
Your app and your opponent’s each add a secret number of their own, so no one, our server included, can choose the dice.
Every roll is worked out from the three. When the match ends, the server shows its number; your app checks it against the fingerprint, works out every roll again and compares. The match-over screen tells you, for example “Fair dice: all 86 rolls checked”.

Count them yourself

Profile › Dice counts every roll of your games, yours and the bots’, and puts each number beside what fair dice give: doubles, opening rolls, coming in from the bar and shots hit. Each number shows its usual range, where 95% of results from fair dice fall. A number is called unusual only when it’s well outside: with several numbers side by side, one often lands just outside by chance alone.

Or roll real dice

Rather trust your own dice? Turn on Settings › Advanced › Roll my own dice, roll real dice on the table and enter each roll in two taps: yours, the bot’s and the opening roll. It starts with your next game. Those games are left out of your dice counts, since the app didn’t roll them.

The recipe, to check by hand

The lock is the SHA-256 of a 32-byte key. A roll is read from HMAC-SHA256, keyed with the game’s key, of the roll’s label followed by :0 (then :1, :2… if more bytes are needed). A byte of 252 or more is skipped, so every face has the same chance; any other byte gives a die of (byte mod 6) + 1. The first two dice read are the roll.

Against a bot, the opening roll’s label is bg-dice-v1:opening:0 (:1, :2… when a tie is rolled again; your die first) and each turn’s is bg-dice-v1:turn:1, bg-dice-v1:turn:2… In a Practice game, a take-back starts a fresh line of rolls: bg-dice-v1:turn:7:line:1.
Online, the key is HMAC-SHA256, keyed with the server’s number, of both apps’ numbers; the labels are bg-online-v1:g1:opening:0, then bg-online-v1:g1:roll:1, …:roll:2… (g2 for the second game of a match, and so on). Your app does this check for you.
A test: with the key 00 01 02 … 1f, the opening roll is 4-6 and the first turn’s roll is 5-4.

Questions

Do stronger bots get better dice?: No. Every bot gets its dice from the same locked key as you. The levels differ only in how well the bot plays.
Can the app see my next rolls?: The rolls are fixed from the start, but the key that makes them stays secret until the game ends, and the bot is only ever given the roll it has to play. Online, no one can work out the dice without all three secret numbers.
Is there real money involved?: No, never. Games are scored in points, and nothing in the app can be bet or won.