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Provably fair

A cryptographic mechanism with which a player can verify for themselves that a game's result was fixed before the bet was placed.

10/10/2026

Provably fair is a cryptographic mechanism that lets a player verify for themselves that a round's result was fixed before the bet was placed and was not changed afterwards.

How it works

Before the game the casino shows the hash of the server seed — a fingerprint that binds the casino to the result formula without revealing the result itself. Each round's result is calculated from three parts: the server seed, your own client seed and the bet's sequence number. When the seeds are rotated, the casino reveals the old server seed and you can check whether its hash matches the one you were shown before the game. If it matches, the result was locked before your bet.

What it covers and what it does not

Provably fair confirms exactly one thing: the result of that particular round was not manipulated. It says nothing about withdrawal speed, bonus rules, customer support or the licence — a casino with honest maths can still drag out a withdrawal or void a bonus through the small print. Those things have to be assessed separately.

What to check

  • Whether the casino has a real verification tool and instructions, not just a "provably fair" logo.
  • Whether you can set the client seed yourself and rotate the seeds.
  • Whether the old server seed is revealed after a rotation.
  • Which games it applies to at all: the mechanism is common in the casino's own crash, dice and mines-type games. Ordinary video slots have their results generated by the provider's RNG, checked by external auditors — there is no seed pair there.

Together with RTP it gives a complete picture of a game's maths. Where each casino stands on this is set out in the ranking.

Verification step by step

  1. Before the first bet, copy the server seed's hash and save it (text or screenshot).
  2. Rotate the seed pair. The casino reveals the old server seed in full.
  3. Compute the SHA-256 hash of the revealed seed and compare it with the saved hash. They must be identical character by character.
  4. Take the server seed, your client seed and the bet number (nonce, which grows with every bet) and compute the round's result with the formula the game publishes. HMAC-SHA256 is often used for this, but the exact formula is in the game's own documentation and may differ between games.
  5. Compare the computed result with what actually came up in the game.

If the hashes do not match, first check the input: a space or line break at the end changes the hash completely. If the input is exactly the same and the hashes still differ, the seed was changed after the hash was shown. Do not argue in chat: write to support, attach screenshots and save the correspondence.

When a check really proves something

  • The hash must have been saved before the bets under that seed pair. If you look at the hash only after playing, it proves nothing, because history cannot be trusted retroactively.
  • Use an independent verifier. A checker on the casino's own page shows what the casino wants you to see; an open source script or a few lines you write yourself is more trustworthy. A guide is here.
  • The formula must be public. If the rule for going from the hash to the game outcome is secret, you can confirm only the hash, not the result.
  • Check several rounds, including the biggest win and the biggest loss, not just one random one.

What it does not change

Provably fair does not tell you how big the house edge is. A verifiable game can still have a worse RTP than a certified slot. The conclusion: check both that the result is honest and what price you pay to play. For technical background on random number generators see the freespin.ee glossary. The seed pair and hash logic is also described as a Wikipedia: commitment scheme, and the signing method as Wikipedia: HMAC.

Guide

Provably fair: what can be proved and what cannot

Provably fair means a particular round's result can be checked mathematically:
the casino publishes a hash before the game, the seed after the game, and you can calculate yourself that the result was
not altered afterwards. That is a real proof and one of crypto casinos' few technical
advantages over an ordinary casino.

What it does not prove. Provably fair says nothing about whether the
RTP is good for the player — a fair game with 96% RTP is still a bad game at 90%.
Nor does it prove that the casino pays out: what is verifiable is the round's result, not the
withdrawal procedure or the KYC threshold.

Where you meet it. Almost exclusively in the house's own games — crash, dice, plinko — not
in third-party slots. Those originals games are often also the market's highest RTP:
Stake and BC.Game build a notable part of their offering on it.
Still check the game weighting: a high-RTP original often gives less in
the wagering than an ordinary slot.

At casinos with an Estonian licence fairness is assured differently — through supervision and audit, which can be
checked in the Tax Board's register. Those houses are compared by
freespin.ee.

See also the RTP calculator. Help: 15410.

Related: each bet is distinguished by the nonce; what provably fair does not say about the house edge is calculated in the post the maths of original games.

Wrote and testedMarten KaskEditor-in-chief
Fact-checkedRasmus KuuskEditor for crypto payments and security
Verified October 2026 · Independent, not funded by any operator