Provably fair games: verify every round yourself

Provably fair means you do not have to take a casino's word that a round was random. The result is fixed by a commitment made before you bet, and you can recompute it afterwards. This guide explains the building blocks and shows how to check a round on JOKR. It is for adults only (18+), and verifying a round never changes how a game pays.

The building blocks

• Server seed: a secret value chosen by the server. Before the round, only its hash is shown to you.
• Client seed: a value that comes from your side, so the server cannot know the full input in advance. Where a game uses one, it is shown in the round details.
• Nonce: a counter that goes up with each round, so the same seeds never produce the same result twice.
• Hashing: a one-way function (SHA-256) that turns a seed into a fixed fingerprint. You cannot work backwards from the fingerprint, but anyone can check that a revealed seed matches it.
• HMAC: a keyed hash used to turn the seed material into a stream of numbers that decides the outcome.

Why the commitment matters

The hash is published before betting opens. After the round, the seed is revealed. If the hash of the revealed seed matches what you saw earlier, the server could not have changed the seed after seeing your bet. Then you recompute the outcome from the seed and check that it matches what you were shown.

Which Originals can be verified

JOKR has 6 Originals: BlackJOKR, JOKR Duel, JOKR Ballz, JOKR Spin, JOKR Crash, JOKR Mines. They do not all use the same scheme:

• JOKR Crash and JOKR Mines are provably fair and can be checked round by round.
• JOKR Spin, and JOKR Duel when played against the house, use a commit-reveal scheme.
• BlackJOKR deals from a six-deck shoe shuffled with a cryptographic generator. It is not commit-reveal, so there is no seed to verify, but every hand is recorded server-side.
• JOKR Ballz is a server-side physics simulation and is also not commit-reveal.

The full list is on the Originals page.

How to verify a round

1. Before you play, note the hash of the seed shown for the round.
2. Play the round to the end. The seed and salt are revealed.
3. Open the verifier on the Fairness & RNG page.
4. Paste in the revealed values. The verifier recomputes the hash, which must match the one you noted.
5. Check the recomputed result: the crash point in Crash, or the mine positions in Mines.

Rounds played under the current rules carry a version tag at the start of the salt, so you can tell which rules apply. The exact formulas are written in the rules section of each game page.

What provably fair does not tell you

A verified round proves the result was not altered. It does not predict future rounds or change the odds. The house edge is set by each game's written rules. Play within limits you set, and see responsible gaming if you need support.