PROVABLY FAIR VERIFIER

WHAT IS PROVABLY FAIR?

Provably fair is a cryptographic verification system used by crypto casinos to prove that game outcomes are genuinely random and have not been manipulated. Unlike traditional online casinos where you must trust the operator, provably fair systems let you mathematically verify every single bet you place. If you are new to the concept, our guide on how provably fair gambling works breaks down the math step by step.

The system relies on three key components: a server seed generated by the casino, a client seed that you can set yourself, and a nonce that increments with each bet. These three values are combined using HMAC-SHA256 hashing to produce a deterministic result. Because the server seed is committed (hashed) before the round begins, the casino cannot change it after seeing your bet. And because you control the client seed, the casino cannot predict the final outcome.

This approach shifts the trust model from blind faith to mathematical proof. After each round, you can take the revealed server seed, combine it with your client seed and nonce, and independently verify that the game result matches what the casino displayed. If the results match, the game was provably fair. If they do not, you have cryptographic evidence of manipulation.

HOW DOES PROVABLY FAIR VERIFICATION WORK?

The verification process follows a straightforward cryptographic protocol that any player can independently execute:

1. Before the round: The casino generates a random server seed and shows you its SHA-256 hash (the "hashed server seed"). This commits the casino to a specific seed without revealing it. You can also set your own client seed at any time.
2. During the round: The casino combines the server seed, your client seed, and the current nonce using HMAC-SHA256 to produce a hash. This hash is then converted into a game result using a game-specific algorithm (crash multiplier, dice roll, mine positions, etc.).
3. After the round: The nonce increments by one. When you rotate your server seed, the previous unhashed server seed is revealed. You can now verify every bet made with that seed pair.
4. Verification: Take the unhashed server seed, your client seed, and the nonce for any specific bet. Run them through the same HMAC-SHA256 function and game algorithm. If your calculated result matches the casino's displayed result, the outcome was fair.

The HMAC-SHA256 function is a one-way cryptographic hash. Given the same inputs, it always produces the same output. But it is computationally impossible to reverse-engineer the inputs from the output or to find different inputs that produce the same hash. This mathematical property is what makes the system tamper-proof.

SUPPORTED CASINOS & GAMES

We only list a casino as verified when we have confirmed, byte-for-byte against its published documentation, that it uses the exact scheme this tool implements: HMAC-SHA256(server seed, "clientSeed:nonce:cursor") with each 4 bytes converted to a number in [0,1). We will not hard-code a casino whose format we could not confirm from a primary source — doing so would produce wrong results and a false sense of security. See our list of the top crypto casinos ranked by deposit volume or the best provably fair casinos.

Per-casino seed checkers, pre-set with the right scheme and seed-finding steps: Stake Seed Checker · Shuffle Seed Checker · Roobet Seed Checker.

Games this tool reproduces (for verified / Stake-style casinos): Crash, Dice, Limbo, Roulette, Mines, Plinko, and Keno. The per-game maths for Dice, Limbo, Roulette, Mines, Plinko, and Keno are validated against published reference test vectors. Crash is operator-dependent — see the note shown with each crash result. Casinos also run third-party slots and live-dealer tables, which use traditional RNG or live video and are not verifiable this way.

VERIFY A SPECIFIC GAME

Prefer a page pre-set to one game, with that game’s exact formula and a worked, reproducible example? Use a dedicated verifier:

• Crash Provably Fair Verifier — recompute any crash multiplier from your seeds.
• Dice Provably Fair Verifier — check any 0.00–100.00 dice roll.
• Limbo Provably Fair Verifier — recompute any limbo multiplier.
• Mines Provably Fair Verifier — reveal the exact mine layout.
• Plinko Provably Fair Verifier — trace the full left/right path.
• Keno Provably Fair Verifier — recompute all 10 drawn numbers.
• Roulette Provably Fair Verifier — check the winning pocket (European 0–36).

HOW THIS VERIFIER WORKS & WHY YOU CAN TRUST IT

This is a static page. There is no account, no upload, and no back end. Everything below happens in your own browser, and you can confirm all of it by opening your browser’s developer tools or simply reading the page source.

• It runs the same open-source algorithm the casinos publish. The hashing is your browser’s built-in Web Crypto crypto.subtle HMAC-SHA256 — the identical primitive Stake, Shuffle, and other Stake-style casinos document. The per-game conversions port a widely-used open-source reference implementation and reproduce its published test vectors to the exact decimal.
• Nothing is sent to a server. Your server seed, client seed, and nonce never leave the page. No network request is made when you click Verify (check the Network tab) and we store nothing.
• It is deterministic, so you can cross-check it. The same inputs always produce the same output. Run the same seeds through your casino’s own verifier, or any other independent tool, and you should get an identical hash and result. If two independent tools agree, the round was fair.
• We do not ask you to trust our numbers. Every result shows the full HMAC hash and a step-by-step breakdown of how the outcome was derived, so you can follow the maths yourself rather than taking it on faith.

What this tool does not do: it cannot predict future results (the server seed is only revealed after you rotate it), it does not test or rate a casino’s honesty for you, and it makes no claim about how many rounds have ever been checked. It is simply a transparent calculator for the published provably-fair maths.

WHY SHOULD YOU VERIFY YOUR RESULTS?

Verification is the entire point of provably fair gambling. Without independent verification, provably fair is just a marketing buzzword. Here is why every player should verify at least some of their results:

Trust but verify. Even reputable casinos could theoretically be compromised by rogue employees, software bugs, or security breaches. Provably fair verification is your insurance policy. By checking results yourself, you confirm the system is working as intended.

Detect anomalies early. If a casino were to tamper with results, verification would catch it immediately. The HMAC-SHA256 hash would not match. While no major crypto casino has been caught cheating through provably fair manipulation, regular verification keeps the industry honest.

Understand the math. When you verify results, you gain a deeper understanding of how casino games work mathematically. You can see the house edge built into the algorithm (for example, the 4% house edge in Crash games) and make more informed decisions about your play.

Build confidence. Many players experience losing streaks and wonder if the games are rigged. Verification eliminates this doubt entirely. When you can prove mathematically that every result was fair, you can focus on strategy and bankroll management instead of worrying about manipulation.

PROVABLY FAIR CALCULATOR

People search for this tool under several names — provably fair verifier, provably fair checker, fairness calculator, seed checker, or hash calculator. They all describe the same thing: a calculator that takes your server seed, client seed, and nonce and works out the game outcome they produce. The tool at the top of this page is exactly that.

To use it as a calculator, paste your revealed (unhashed) server seed, your client seed, and the nonce of the bet you want to check, pick the matching casino scheme and game, and press Verify. It recomputes the HMAC-SHA256 hash and converts it into the same outcome the casino should have shown — a crash point, dice roll, limbo multiplier, roulette pocket, mine layout, plinko path, or keno draw. Because the calculation is deterministic, the number you get here should match your casino’s result and any other independent calculator exactly. If it does, the bet was fair; if it does not, double-check that you used the revealed server seed and the correct nonce and casino scheme.

IS THERE A PROVABLY FAIR PREDICTOR?

No — a provably fair predictor is not possible, and any tool claiming to be one is a scam. The entire point of the provably fair design is that outcomes cannot be known in advance. The casino commits to a server seed by publishing only its hash before you bet, and the unhashed server seed is revealed only after you rotate it. Without that unhashed seed, the HMAC-SHA256 output is computationally impossible to predict, so there is no way to know a crash point, dice roll, or mine layout ahead of time.

This verifier is strictly a post-bet checker: it confirms that a result which has already happened was generated honestly. It can never tell you what the next round will be. Be very wary of any "predictor", "hack", "signal", or paid bot that promises future results — at best it is guessing, and at worst it is designed to take your money. We explain the maths behind why prediction is impossible on our dedicated page: Is there a provably fair predictor?

HOW TO FIND YOUR SEEDS

Each casino stores your seed information in a slightly different location. Here is how to find your seeds on the most popular platforms:

1. Stake: Click your username in the top-right corner, go to Settings, then select the Fairness tab. You will see your active server seed hash, client seed, and total bets (nonce). Click "Rotate" to reveal the previous server seed for verification. You can also change your client seed at any time.
2. Roobet: Click your avatar in the top-right corner, then select Fairness from the dropdown. Your current hashed server seed, client seed, and nonce are displayed. To reveal the unhashed server seed, click "Change Seeds" which will rotate to a new seed pair and reveal the old one.
3. BC.Game: Navigate to your profile icon, then select Provably Fair. BC.Game shows your active and previous seed pairs with the nonce counter. Click "Rotate Seed Pair" to generate new seeds and reveal the previous server seed for verification. You can also view bet-level fairness data from your bet history.

Remember: the server seed is only revealed after you rotate it. This is by design — if you could see the server seed before betting, you could calculate the outcome in advance. The hashed version shown during active play proves the casino committed to a specific seed without revealing it.