What provably fair means

The idea: a sealed envelope

Before you bet, the house seals its secret in an envelope and shows you the envelope’s fingerprint: the SHA-256 hash of its server seed. You add your own ingredient, the client seed. Each result is mixed from both, plus a counter.

Later the envelope is opened. You check that the secret matches the fingerprint you saw, and that it produces exactly the results you got.

The three ingredients

• Server seed: the house’s secret random value. You see only its hash until you rotate it.
• Client seed: yours. Change it to anything you like, whenever you like.
• Nonce: a counter that goes up by one with every bet, so no two bets share an input.

Why it works

• A hash can’t be reversed, so seeing it tells you nothing about the results to come.
• Any change to the seed changes its hash completely, so the seed can’t be swapped after you bet.
• You can change your client seed at any time, so the server seed can’t have been chosen to suit it.

How to check a result

1. Rotate your seed

   On the Fairness page, rotate your seed pair. The old server seed is revealed.

2. Compare the hash

   Hash the revealed seed with SHA-256. It must match the hash you saw before betting.

3. Recompute

   Put the seed, your client seed and the nonce into the verifier, or any HMAC-SHA256 tool, and apply the game’s formula.

Each game’s formula is on its own page, for example Dice, Roulette and Plinko. The full method is on Provably fair.

Shared rounds and prize draws

• Crash rounds are shared, so they come from a hash chain fixed before the first round.
• Prize draws publish their seed’s hash when they open and reveal the seed straight after the draw.

What provably fair doesn’t mean

It proves a result wasn’t changed after you bet. It doesn’t remove the house edge: the instant games return 90% of stakes over time, and Crash, Dice and Mines 90%. And a losing streak never makes a win more likely.

Frequently asked questions