Seeds, hashes and house edge

How provably fair works step by step, and where its reach ends

A round built on seeds can be recomputed by the player once it is over. This guide walks through the hash, the client seed and the nonce, and shows which questions about your money that check leaves open.

Provably fair is a way of building a game round so that you can recompute its result yourself once the round is over. The casino commits to a secret value before you bet, you add a value of your own, and afterwards the secret is revealed so the arithmetic can be repeated outside the casino. Done properly, that gives you a mathematical receipt for a single round.

That receipt is narrow. It tells you nothing about the house edge, the cap on withdrawals, the identity clause or the licence behind the domain. The five checks behind the ranking on the home page therefore sit next to the seed check, not inside it.

The three values that decide a provably fair round and the check you can run afterwards. It shows that the round was not altered; it says nothing about house edge, caps or payout.

The three values behind a provably fair round

Every scheme that uses the label rests on the same three ingredients, even if the names on the settings screen differ.

Server seed. A random string the operator generates and keeps secret while it is in use. Before any bet, you see only its hash: a fingerprint from which the seed itself cannot be worked back.
Client seed. A string that comes from your side. Most games fill it in automatically, and a good implementation lets you replace it with anything you type.
Nonce. A counter that goes up by one with every bet made under the same pair of seeds, so bet 1 and bet 2 never produce the same result.

The game combines the three, runs them through a hash function and turns part of the output into a number: a dice roll, a card, a multiplier. Because the server seed was fixed before your client seed was known, the operator cannot pick a seed that suits a particular bet.

Worked example at a 1% house edge: the multiplier is 99 divided by the chance in per cent. Halve the chance and the payout roughly doubles; the expected loss per bet stays at 1%.

Checking a round step by step

The verification itself takes a few minutes and needs no special software beyond a hash calculator.

Before playing, open the fairness settings and write down the hash of the active server seed together with your client seed.
Play as usual. Each bet in the history carries its nonce.
Rotate the seed pair. Only then does the casino reveal the old server seed in plain text, and a new hashed seed takes its place.
Hash the revealed server seed yourself. The result must match the hash you wrote down in step 1, character for character.
Feed server seed, client seed and nonce into the formula the game publishes and compare the number with the result in your history.

If step 4 fails, the seed was swapped after the fact. If step 5 fails, either the formula on the page is incomplete or the result was altered. Both are worth a screenshot with a date and a message to support, as described in the guide on raising a complaint with a casino.

A named example: Aviator by Spribe

Spribe describes its scheme for Aviator on its own fairness page. On the operator's side, a server seed made of 16 random symbols is created. Before the next round starts, a player can open the fairness settings and see that seed as a SHA256 hash. Client seeds come from players. At the start of each round, Spribe combines the server seed with the players' client seeds, hashes the lot with SHA512, and reads the multiplier from that output. Every round in the game history carries an icon that opens its check, and a player can change the client seed. The same logic as the list above, packaged for a shared multiplayer round.

What operators in the ranking say about fairness

Three casinos in the ranking print a fairness line on their own pages, read on 2 September 2026.

Bitsler writes in its homepage copy that all of its games are built on provably fair technology. Treat that as the operator's claim: slots from outside studios run on the studio's own random number generator, and no seed chain on Bitsler's side can reach into them.
Rainbet puts its Originals on seed-based fairness logic; for Case Battles and EOS Roulette, the randomness is taken from blocks of the EOS blockchain.
Wolfbet explains in its FAQ that the server seed can be changed on its fairness page, either per session or per bet ID.

None of these lines appears in the score. They describe a game mechanism, while the five checks look at the terms and the licence.

What a provably fair check proves, and what it leaves out

A successful verification shows one thing: the result of that round follows from seeds that were fixed before you bet. It does not show that the game is generous.

Here is what stays outside:

House edge. A dice game can be perfectly verifiable and still keep 1% of everything staked over time. The seed proves the roll; the payout table sets the price.
Withdrawal rules. Caps such as Wolfbet's US$8,000 a week (cl. 15 §5) or instalments at Rocketpot (cl. 11.5) are terms, not game code. The page on withdrawal limits covers them.
Identity checks. Whether ID is asked before a payout is set in the terms, as the guide to verification shows.
Third-party slots. They sit outside the casino's seed chain altogether.
The licence. A verified round says nothing about who holds the certificate for the domain.

House edge in plain numbers

Seed-based games usually publish their edge, which makes the arithmetic easy to follow. At a 1% house edge, the multiplier on a winning bet equals 99 divided by the chance of winning in per cent. A 50% chance pays 1.98x; a 25% chance pays 3.96x; a 10% chance pays 9.9x. Halving the chance roughly doubles the multiplier, but the expected loss per bet stays at 1% of the stake, whatever the setting.

That expected loss adds up. Staking €1 two hundred times at a 1% edge means an expected loss of €2 over the series. A single session can end well above or below that figure, yet the more you stake in total, the closer the outcome tends to move towards it. The page on responsible gambling uses the same arithmetic to set a budget before you start.

Frequently asked questions about crypto casinos

If a round is provably fair, can the casino still treat me unfairly?

Within limits, yes. A verified round rules out one thing going unnoticed: changing the result of a round after the seeds were fixed. Everything else is still possible under the terms, such as a withdrawal cap, a request for documents before a payout or a closed account. Read the verification clause and the limits section as well, because a verified roll protects the game result and nothing beyond it.

Why can I only verify after rotating my seed?

While a server seed is active, revealing it would let you calculate every future result under that seed pair in advance. The casino therefore shows only its hash until you rotate. After rotation the old seed becomes public, and you can check every bet that was made with it, one nonce at a time, against the hash you noted earlier.

Should I change the client seed myself?

Changing it is a simple way to make sure the operator did not pick both values. Any string works, for example a few random words. Write down the new value with the date, together with the hash of the active server seed, so you have everything you need when the time comes to rotate and check.

Do slots from well-known studios use the same seeds?

Usually not. A studio's slot runs on that studio's own random number generator and is certified through the studio's own route, not through the casino's seed chain. A homepage line about fairness for every game cannot extend to those titles, so look for the fairness icon inside the individual game.