A cryptographic method that lets you verify a specific game result was not altered after you bet. It proves the individual round was not tampered with, but it does not prove the operator will pay you or that the house edge is fair.
The mechanism
Before the round, the operator commits to a secret value by publishing its hash. You contribute a value of your own, called a client seed. The result is computed from both. Afterwards the operator reveals the secret, and you can recompute the hash and confirm it matches what was published before you bet.
If the operator had changed the secret to alter your result, the hash would no longer match. That is the proof.
What it genuinely proves
That this specific round was determined by values fixed before you played, and was not adjusted after the fact. For dice, crash and similar in-house games, that is a real guarantee and better than taking an RNG on trust.
The two things it does not prove
It does not prove the operator will pay you. Verifiable round outcomes and a refused withdrawal are entirely compatible. Provably fair addresses game integrity, not solvency or willingness to pay. The licence addresses those, which is why a provably fair unlicensed operator is still a weak proposition.
It does not mean the odds are good. The house edge is set separately, in the payout table. A provably fair dice game can carry a 5% edge, which is worse than most slots, and the proof will confirm every unfavourable roll was honestly computed.
Where it does not apply
Third-party slots and live dealer games are not provably fair, because the studio controls the RNG and does not expose a commitment scheme. Those rely on independent lab testing instead. So a crypto casino advertising provably fair usually means only its own small set of in-house games.
How to read it
Treat it as a genuine plus on in-house games and as no substitute for a licence. Verify the licence first, then enjoy the proof.