What is provably fair?

Definition

Provably fair is a method, used mostly by crypto casinos, that lets a player check after the fact that the outcome of a game round was determined by values fixed before the bet was placed and could not have been changed by the operator. It combines a server seed (committed in advance as a hash), a client seed the player can set, and a nonce that counts rounds; the outcome is a function of the three. (source: BGaming provably fair, iGaming Times glossary)

It is a transparency mechanism, not a fairness guarantee about the odds. A provably fair game can still have any RTP its maths defines; what the player can verify is that the operator did not alter the result of that specific round. (source: iGaming Times glossary)

Example

Worked example, BGaming's scheme (source: BGaming provably fair): before the round the game generates the outcome (Result) and a Secret, hashes them with SHA-256 and shows the player Hash(Result + Secret). The player enters a client seed of their own. After the round the game reveals Result + Secret; the player hashes them with any SHA-256 tool and checks the hash matches the one shown before the bet, then applies the client seed to the Result in the way the game defines (BGaming publishes the rule per game) to arrive at the final result shown. A changed outcome would not match the pre-round hash.

Formula

• Commitment (BGaming): published_hash = SHA-256(Result + Secret), shown before the bet. (source: BGaming provably fair)

• Final result (BGaming): final = apply(client_seed, Result), a game-specific rule published with the game; the client seed is set by the player before the bet. (source: BGaming provably fair)

• Verification: SHA-256(revealed Result + Secret) == published_hash and apply(client_seed, Result) == shown result. (source: BGaming provably fair)

• Seed-pair variant used by many crash and dice games: a server seed committed as a hash, a client seed and a nonce that counts bets; the round result is derived from the three with a keyed hash (HMAC), so one server seed covers many rounds and is revealed when the player rotates seeds. (source: iGaming Times glossary)

Comparison

• Provably fair vs RNG certification: certification is a third-party audit that the generator and RTP behave as declared across millions of rounds; provably fair is a per-round check the player can run. Studio games from an aggregator are certified, not provably fair; crypto-native originals (dice, crash, mines, plinko) are usually provably fair. (source: iGaming Times glossary)

• Provably fair vs on-chain: provably fair runs off-chain on the site's servers with cryptographic commitments; on-chain games publish randomness and settlement on a blockchain. Different trust models, both verifiable.

• What it proves: the round was not changed after commitment. What it does not prove: that the game's odds are good, that payouts will be honoured, or that the site is licensed.

Impact on the owner

• Players in the crypto segment expect provably fair on original games and look for the verification page; its absence is read as a warning sign in that audience.

• Provably fair games are usually the platform's own originals with high RTP (97–99%) and low content cost, which changes the margin mix compared with studio slots.

• It does not replace certification for regulated markets; a licence still requires audited RNGs for the catalogue. (source: iGaming Times glossary)

• Publish the verifier and keep seeds rotatable: a player must be able to change the client seed and reveal past server seeds, or the mechanism is not credible. (source: BGaming provably fair)

How it works in practice

The platform generates a server seed, stores it, and shows only its hash. The player sets or accepts a client seed. Each bet uses the current pair plus a nonce; the result is derived deterministically and shown. When the player rotates seeds, the old server seed is revealed and every past round under it becomes checkable in the site's verifier or with an open-source script. Operators keep seed-generation and reveal logs for disputes and audits. (source: iGaming Times glossary)

FAQ

• 01Does provably fair mean I cannot lose?+
  No. It proves the result was not tampered with; the odds are what the game's RTP says.
• 02Are slots from big studios provably fair?+
  Usually not; they are RNG-certified by a laboratory instead. (source: iGaming Times glossary)
• 03Can a site fake provably fair?+
  Not for a round whose server-seed hash was published before the bet, if the player verifies; a site that never reveals seeds or blocks seed changes is not provably fair in practice.
• 04Do I need to verify every round?+
  No. The possibility of verification is the point; most players spot-check.
• 05Is provably fair required by law?+
  Not generally; licences require certified RNGs. Provably fair is a crypto-market expectation.

Related

• RTP · House Edge · Game Aggregator · GGR