Provably fair is a verification method where a game publishes a hash of its outcome before the round and lets the player recompute it afterwards — proving the result was not changed after the bet.

What "provably fair" means

Provably fair is a scheme — popularised by crypto casinos and crash games — in which the game proves to the player that the outcome was fixed before the bet was placed and was not altered afterwards. The proof is cryptographic: hashes and seeds, not trust in the operator.

How the standard scheme works

Before the round, the server generates a secret server seed and publishes a hash (a commitment) of it. A hash cannot be reversed, so the player cannot see the seed yet — but the player now has proof of what it was.
The player holds a client seed, often chosen or changed by the player themselves.
The outcome is derived from a function of (server seed, client seed, nonce) — e.g. a crash multiplier or dice roll.
After the round (or when the player rotates seeds), the server reveals the original server seed.
The player recomputes the hash and the outcome. If they match what was played, the round was fair.
The key property: the outcome existed — committed and hashed — before the player bet, and the player can verify it independently afterwards. Changing a result after seeing the bet would break the published hash.

Provably fair vs certified RNG

A certified RNG relies on third-party audit: the lab certifies the game, the player trusts the certificate.
A provably fair scheme relies on mathematics the player can run: verification is self-service.
They are not competitors — many crypto games are both (certified RNG behind a provably fair interface). Provably fair adds player-facing verifiability on top of certification, not instead of it.

Where it fits in a catalogue

Provably fair matters most for crash, dice, mines and other simple fast formats popular in crypto-first markets. For slots and live casino, studio certification remains the norm. An operator's catalogue usually contains both: verifiable crypto formats for crypto-native players, and certified slot/live content from major studios for everyone else.

GamingAPI's catalogue includes crash formats (Spribe's Aviator among them) alongside studio-certified slots and live tables, all launched through one API and settled through the same wallet — the fairness model is a property of each game, not of the integration.