Online, you cannot watch the dice. Provably fair is a way for a casino to commit to the randomness of every round before you bet, so you can check afterwards that nothing was changed.
The three ingredients
- Server seed: a random secret generated by the casino. Before you play you only see its hash, a fingerprint that cannot be reversed but changes completely if the seed changes.
- Client seed: a value on your side. You can set it yourself, so the casino cannot pick a server seed that works against a seed it does not know.
- Nonce: a counter that goes up by one with every bet, so each bet with the same seed pair gets a different result.
How a result is made
The casino combines the three with a cryptographic function (commonly HMAC-SHA256), turns the output into a number between 0 and 1, and maps that number to the game: a dice roll, a crash multiplier, a card. The same inputs always give the same result, which is what makes checking possible.
What it proves, and what it does not
- Proves: the result of each bet was fixed by seeds chosen before the bet, and the casino did not swap the server seed while you played.
- Does not prove: that payouts are generous. The house edge sits in the payout table (for example, 0.99 ÷ chance on a 1% edge dice game). See house edge and RTP.
- Does not cover: third-party slots and live tables, or whether the casino pays withdrawals. For that, see the safe crypto casino checklist.
Verify a round yourself
- Note the hashed server seed and set your own client seed in the casino's fairness settings.
- Play some rounds, then rotate the seed pair to reveal the server seed.
- Open the provably fair verifier, paste the seeds and a nonce, and compare the hash and results with your bet history.
Good habits
- Change your client seed now and then, and rotate before long sessions you want to audit.
- Spot-check a few bets, especially big wins or losses. One mismatch is worth asking support about.
- Prefer casinos that publish their exact formulas: Stake and Duel both have fairness pages for their originals.
Quick answers
Does provably fair mean I will win?
No. It proves the casino did not change a result after you bet. The house edge is still built into the payouts.
Why do I need to rotate my seed to verify?
The server seed must stay secret while it is in use, otherwise players could predict results. Rotating ends the pair and reveals the old seed, so you can check every bet made with it.
Are slots and live games provably fair?
Usually not. Third-party slots and live dealer games rely on certified random number generators and audits instead of seeds you can check yourself.
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