The Mechanism
Before you play, the site commits to a hashed server seed — publishing the hash locks the value without revealing it. Your client seed (which you can change) combines with it and a nonce to generate each outcome. When the server seed rotates, the old one is revealed: hash it yourself and it must match the original commitment, proving results weren't altered mid-session.
Verifying in Practice
Sites like Stake and BC.Game expose seed management in settings, and independent verifier tools recompute outcomes from revealed seed pairs. Change your client seed after big sessions and spot-check occasionally — the point of the system is that you can, not that you must every roll.
What It Doesn't Cover
Provably fair proves outcome integrity, not favorable odds — a verifiably fair game still carries its stated house edge. It also doesn't extend to sports betting (real-world outcomes need no RNG) or guarantee the site pays withdrawals. Fairness tech complements, but never replaces, choosing reputable operators.