1
The casino commits
Before your session starts, the casino generates a server seed and publishes its SHA256 hash. The hash is a one-way fingerprint - the casino cannot change the seed without changing the hash you already saw.
Education
Provably fair, explained
A 4-minute crash course in how the best crypto casinos prove they cannot rig a result, plus links to the verifier you can run yourself.
Provably fair gambling is a cryptographic guarantee that the casino cannot change the outcome of a bet after seeing it. It does not guarantee the casino is honest about its bankroll, its withdrawal queue or its bonus terms - but it does prove that the dice, the deal or the spin you just played out was sealed before you placed the bet.
2
You contribute entropy
You generate or modify a client seed. Because the round result is a function of both seeds, the casino cannot predict the outcome any better than you can - and you cannot predict it any better than they can.
3
The round is rolled
HMAC-SHA256 of the (server seed, client seed, nonce) triple produces a deterministic hash. The first few bytes are folded into a number in the range each game requires - 0 to 99.99 for dice, 0 to 1 for crash, etc.
4
You verify after the fact
When you rotate the server seed, the casino reveals the original unhashed seed. You SHA256 it, confirm it matches the hash you saw at the start, then re-roll every round in our seed analyzer to make sure the casino did not lie about the result.
TL;DR
If the unhashed seed the casino reveals matches the hash they showed at the start, and our verifier produces the same roll the casino displayed, the round was fair. If either check fails, the casino was caught.
Open the seed analyzer