People who ask "Why would a casino call me?" can check the answer themselves, 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.
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 for 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 page.
Further questions
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.
Can a player rotate seeds on request?
Yes. Rotating ends the current pair, reveals the old server seed for checking and starts a fresh hashed seed for the next rounds.
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.
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.
Does provably fair prove the house edge is fair?
No. It only proves a result was not altered after the bet; the edge built into the payouts is published separately and varies by game.
When is the server seed revealed?
Once it is retired through seed rotation; while in use it stays hidden, because knowing it would let a player predict every result.