People who ask "What is provably fair?" 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 is over.
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 page.
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.
Each result comes from combining the server seed, the client seed and the nonce into a new hash, then turning part of that hash into a number the game can use: a dice roll, a card or a multiplier. The formula is published by the casino, often with sample code. Different games use different conversions, so a verification tool has to match the game in question, and the published formula is what makes an independent check possible at all.
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.
Publishing the hash first locks the casino in, since any later change to the hidden seed would produce a different fingerprint.
Once it is retired through seed rotation; while in use it stays hidden, because knowing it would let a player predict every 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.