What it proves, how to check it, and what it doesn't cover.
Not available to residents of Ontario or Alberta. This page is for players 19+ elsewhere in Canada (18+ in Manitoba and Quebec).
By James Burke · Updated Oct 13, 2026
The idea in one paragraph
"Provably fair" is a way of letting you check, after the fact, that a game result wasn't changed once you placed your bet. It uses a cryptographic commit-reveal scheme: the site locks in a secret value before you play, shows you a fingerprint (hash) of it, then reveals the secret later so you can confirm it matches. It's mostly found at crypto casinos.
The three ingredients
Server seed: a secret random string the site generates. Before you play you only see its SHA-256 hash. Once the hash is published, the seed can't be swapped without the hash changing.
Client seed: a value you (or your browser) supply. Because the site committed to its seed before knowing yours, it can't pre-pick a server seed that gives a result it likes.
Nonce: a counter that goes up by one with each bet, so every round under the same seed pair gives a different result.
The game typically combines the three with HMAC-SHA256 and converts the output into the result, such as a dice roll or a card.
How to verify a result
Before betting, note the server seed hash and your client seed.
After you finish with that seed pair, rotate it. The site then reveals the old server seed.
Hash the revealed server seed with SHA-256 and check it matches the hash you were shown, character for character.
Re-run the server seed, client seed and nonce through the game's published algorithm and confirm you get the same result.
Verification is retrospective. You can only check rounds after the seed pair is retired. Use an independent verifier where you can, not only the casino's own tool.
What provably fair does NOT prove
It doesn't remove the house edge. It proves the outcome came from the committed seeds. The game's pay table still sets the casino's margin.
It doesn't make a site licensed or safe. Withdrawals, account terms and dispute handling are separate questions.
It only covers the games that support it. Slots and live dealer games from standard providers usually rely on other methods.
Provably fair vs traditional RNG testing
Most online casinos use a random number generator (RNG) tested by an independent lab and show a certificate. Many casinos link to an eCOGRA or GLI certificate. That model asks you to trust the lab. Provably fair lets you check individual rounds yourself. Each has limits, and neither tells you whether a game's return is good. For that, check the RTP or house edge.
FAQs
Does "provably fair" mean the casino is fair overall?
No. It lets you verify that a round's result matches the seeds it committed to. It says nothing about pay tables, terms, licensing or withdrawals.
Do I need to code to verify a result?
No. Any SHA-256 tool can check the hash, and open-source verifiers can recompute the result. Some tech familiarity helps.
Does it change my odds?
No. The house edge is the same whether or not you verify.