Provably fair games explained: how to verify a crypto casino bet
Provably fair is a method that lets you check, after a round, that its result was fixed before you bet and not changed afterwards. The casino commits to a hidden server seed by showing its cryptographic hash, you add your own client seed, and once the server seed is revealed you can recompute the result yourself.
The pieces: seeds, nonce and hash
- Server seed: a secret value generated by the casino. Before you bet, it shows you only its hash (for example SHA-256) — a fingerprint that identifies it without revealing it.
- Client seed: a value you choose or change yourself. Because the casino doesn’t know it in advance, it can’t prepare a result for you.
- Nonce: a counter that goes up with every bet, so each round with the same seeds gives a different result.
Each round’s result is calculated from all three. When you change seeds, the casino reveals the previous server seed and you can check that its hash matches the one you were shown at the start.
How to verify a round, step by step
- Before playing, note the server-seed hash the game shows you.
- Set your own client seed.
- Play, and note the nonce of the round you want to check.
- Change seeds: the casino reveals the server seed that was used.
- Hash that seed and compare it with the one you noted. If they match, it wasn’t changed.
- Recompute the result with the casino’s verifier or your own script, using both seeds and the nonce.
Where you’ll find it
- BGaming says it was the first major provider to introduce provably fair, using SHA-256 hashes and a player-chosen seed. Games like Plinko and Aztec Magic Deluxe support it.
- Stake: its 31 Stake Originals (Mines, Dice, Plinko, Crash and more) are provably fair.
- Rainbet: its originals use a client seed, server seed and nonce; Case Battles and EOS Roulette draw randomness from EOS blockchain blocks.
- BC.GAME: its originals show the hashed server seed before each round.
Try it yourself
Our free games use exactly this system, with a panel where you can see the hash, change your seed and verify any round.
Try it free: Play our free, provably fair versions with fun money: Plinko · Crash · Mines · Dice
What it proves — and what it doesn’t
It proves the round’s result was fixed before your bet and wasn’t changed afterwards.
It doesn’t prove:
- that the casino is licensed or pays withdrawals;
- anything about third-party studio slots, which normally run on random number generators certified by test labs rather than this system;
- that you’ll win: the house edge is still there — it’s just verifiable.
Sources
- BGaming: how its provably fair system works
https://bgaming.com/provably-fair - Stake: provable fairness for Stake Originals
https://help.stake.com/en/articles/5241133-provable-fairness-for-stake-original-games - Rainbet: provably fair originals and EOS-based games
https://web.archive.org/web/20261021122648/https://rainbet.com/ - BC.GAME: provably fair originals
https://web.archive.org/web/20261102050742/https://bc.game/