Those asking "Why would a casino call me?" can check the answer on their own, round by round. Provably fair games let a player confirm that a result was fixed before the bet and stayed untouched afterwards, using nothing but a published hash and a short calculation. The casino commits to its part of the result in advance, the player adds a part of their own, and the two combine into the outcome. Anyone can repeat the calculation once the round has ended.
Provably fair proves that a result was not altered after the bet, and nothing more. It says nothing about the house edge built into the game's payouts, which is published separately and varies from game to game. Only some games at a casino use the system, usually its own dice, crash or card games, while titles from outside studios rely on other forms of testing. The result history lists which rounds are open to checking.
Checking a round takes a few steps. After rotating the seeds, the player copies the revealed server seed, confirms that its hash matches the one shown earlier, and enters it with the client seed and nonce into a calculator. The calculator should reproduce the recorded result digit for digit. Casinos provide their own verification page, and independent calculators run the same formula, which removes the need to trust the casino's own tool.
Before any bet, the casino generates a secret value called the server seed and shows only its hash, a fingerprint that cannot be reversed into the seed itself. Publishing the hash first locks the casino in: any later change to the seed would produce a different fingerprint. The seed stays hidden while it is in use, because knowing it would let a player predict every result. Once it is retired, the casino reveals it so it can be checked.
What people also ask
How does the hash become a game result?
The server seed, client seed and nonce combine into a new hash, and a published formula turns part of it into a dice roll, card or multiplier.
What does the nonce do?
A counter that rises by one with every bet made under the same pair of seeds, giving each round a fresh input.
How can a player verify a provably fair round?
Check that the revealed server seed matches the earlier hash, then enter it with the client seed and nonce into a calculator that should reproduce the result exactly.
Why is the server seed hash shown before a round?
Publishing the hash first locks the casino in, since any later change to the hidden seed would produce a different fingerprint.
What is the client seed in provably fair games?
The player's own contribution, set by the browser or typed in by hand, which can be changed at any time so the casino cannot predict it.
Which games use the provably fair system?
Usually a casino's own dice, crash or card games; titles from outside studios rely on other forms of testing instead.