What is provably fair?
Provably fair is a cryptographic receipt for a casino round. Instead of asking you to trust that a crash multiplier or dice roll was random, the casino commits to the result before you bet and hands you the tools to check it afterwards. It is the one genuine transparency innovation crypto casinos brought to gambling — and it is widely misunderstood.
The three ingredients
- Server seed — a secret random string the casino generates. Before you play, it publishes only the SHA-256 hash of it: the commitment.
- Client seed — a string you control and can change at any time. Because it enters the calculation, the casino cannot precompute outcomes for a seed it does not know yet.
- Nonce — a counter that increases by one per bet, so every round under the same seed pair gets a unique result.
How a round is settled
The outcome is derived deterministically, typically as HMAC-SHA256(server_seed, client_seed:nonce). The resulting hash is converted to a game value — a dice roll, a crash point, a card. When the seed pair is rotated, the casino reveals the old server seed. You then check two things: that its SHA-256 equals the pre-round commitment (so the seed was fixed before you played), and that recomputing the HMAC reproduces the results you saw. Our verifier tool does both in your browser.
What it proves — and what it doesn't
A passing verification proves the casino did not move the goalposts after your bet. It does not prove the game is good value. The published math still contains the house edge: a provably fair crash game with a 1% instant-bust chance keeps roughly 1% of all wagers forever, and no verification changes that. Think of it as an integrity check, not an advantage.
It also only covers the games wired into the system — usually the casino's own originals. Third-party slotssettle on the provider's certified RNG servers; their fairness case is lab certification and published RTP, which is exactly the data this site tracks.
Practical hygiene
- Set your own client seed when you start playing, and rotate it occasionally.
- Verify a few rounds after every seed rotation — spot checks keep the system honest.
- If a revealed seed ever fails the commitment check, screenshot everything and escalate; that is the one red flag the system is designed to catch.
- Remember that a verified fair game is still a negative-EV game.
FAQ
Does provably fair mean the game is fair to play?
It proves the outcome was determined before your bet and not altered afterwards. It does not change the odds: a provably fair dice game with a 1% house edge still takes 1% of all wagers long-run. Fair draw, house-favoured math.
Can a casino cheat a provably fair system?
Not on individual rounds without detection — changing a result after the fact breaks the hash commitment. The residual risks sit elsewhere: unfavourable published odds, seed rotation tricks if you never rotate your client seed, and games that are not actually covered by the system.
Are slots provably fair too?
Usually not. Provably fair covers in-house "originals" (dice, crash, plinko, mines). Third-party slots from NetEnt, Pragmatic Play and others run on the provider’s certified RNG servers instead — their fairness rests on lab certification (GLI, eCOGRA) and the published RTP, not on seed verification.
18+ · Gambling always carries a negative expected value for the player. BeGambleAware.org