Provably Fair Games
Game Guide

Three values produce a round. A server seed, which the operator generates and keeps secret while it is in play. A client seed, which your browser supplies and you can change. And a nonce, which counts up by one with every round played on that pair. The result is a hash of the three, mapped onto the game's outcome range by a published algorithm. Because your seed is part of the input, the operator cannot know the result at the moment it commits; because the nonce increments, one seed pair produces a whole verifiable sequence rather than a single number.

The commitment is what makes any of it checkable. Before you play, the operator shows you a hash of the server seed it has not yet revealed. It cannot swap that seed afterwards without breaking the hash it already published. When you rotate to a new pair, the old server seed is disclosed, and you can hash it yourself and confirm it matches the string you were shown at the start.

Verifying a past round is then arithmetic anyone can repeat. Take the revealed server seed, your client seed and that round's nonce, run the hash function the operator documents, and map the output the way its published algorithm says. If the number you produce is the result you were paid on, that round was fixed before you staked. Open-source verifiers exist for the common implementations, and the operator's own tool is not the only one you are allowed to use.

What the check does not cover is everything else. It says nothing about the house edge, nothing about whether a withdrawal is paid, nothing about whether the licence resolves in a register, and nothing about whether the algorithm running is the algorithm documented. It proves one narrow claim precisely — which is more than most lobbies offer, and considerably less than the phrase is usually made to carry.