“Provably fair” is the reason crash exists in its current form. It means the casino commits to the result before you bet and gives you the tools to prove it afterwards. Here is the mechanism and how to use it.
The three ingredients
- Server seed – a long random string the casino generates. Before the round you only see its SHA-256 hash; the seed itself is revealed after the round (or after you rotate seeds).
- Client seed – a string you can set yourself. Because the casino cannot know it in advance, it cannot pick a server seed that beats you.
- Nonce – a counter that increases every bet, so the same seed pair produces a new result each round.
How the crash point is computed
The classic Bustabit method (used, with small variations, by Stake, Shuffle, Roobet and Duel):
- Compute
HMAC-SHA256(server_seed, client_seed:nonce)(some sites just hash the server seed). - Take the first 13 hex characters (52 bits) and convert to an integer
h. - Crash point
= floor((100 × 2^52 − h) / (2^52 − h)) / 100, and 1 in1/edgerounds is forced to 1.00x (that is how the edge is applied).
Because SHA-256 is one-way, the hash published before the round proves the seed was fixed, and the seed revealed afterwards lets you recompute the multiplier and compare.
Verify a round yourself
What provably fair does not do
It does not make the game beatable. The edge is applied inside the formula, in the open. It does not stop a casino from refusing withdrawals or running a different formula than the one it publishes — which is why we only list operators whose verifier we have checked ourselves and whose withdrawals we have timed.
Red flags
- No hash shown before the round.
- No way to set a client seed.
- A “fairness” page that only explains the concept and has no calculator.
- A published RTP with no formula behind it (common on provider crash games — you have to trust the lab certificate instead).
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Max has logged more than 40,000 crash rounds since the Bustabit days and built the simulator and probability tools on this site. He verifies every provably-fair implementation we list by hand, tracks real house edges instead of marketing RTPs, and writes the strategy guides. Favourite cashout: 1.5x, because he likes sleeping at night.
This guide is for information only and is not financial or gambling advice. Crash is a negative-expectation game: no strategy changes the house edge. 18+. Gamble responsibly.