The server seed is a random value generated by the casino from which, together with your own seed, the round's result is calculated. You do not see it before the game — you see only its hash.
The timeline
- The casino generates the seed and shows you the hash. The result is locked from that moment.
- You play, where possible with your own client seed.
- When you rotate the seed pair, the casino reveals the server seed in full.
- You recompute the hash and confirm that it matches the one shown in step 1.
Why rotating matters
Until you rotate the seed pair, the server seed stays unrevealed and the check is unfinished. Practical advice: rotate the seed periodically — before a larger series, or when something feels suspicious. Every rotation closes one verifiable block.
If something is missing
If the casino does not show the hash before the game, does not allow the seed to be rotated or does not reveal it afterwards, then the provably fair badge on the page is decoration. Do the check on one round for real before you start playing with a larger amount.
The houses where the check worked in our tests are collected in the provably fair list.
The seed pair lifecycle, bet by bet
Every bet gets its own sequence number, the nonce, which usually starts at zero and grows by one. Example: if you rotate the seed pair after 150 bets, nonces 0 to 149 belong to one pair and all 150 rounds can be verified after the rotation. The new pair gets a new hash and the nonce starts again. For verification you need the server seed, the client seed and the nonce; only then can you recompute a round's result.
Why the active seed is not shown
If the casino showed the server seed during play, you could compute results in advance, because the client seed and the nonce are known to you. That is why the seed is revealed only after rotation, when that pair is no longer in use. A practical rule follows: if you want to verify a specific big win or loss, rotate the seed pair right after that round, before making more bets, and save the nonce.
What to save
- The hash of the server seed before the first bet.
- Your client seed and the time of rotation.
- The nonces and results of the rounds you care about (a screenshot).
In some casinos the seed pair rotates automatically, for example after a time or a number of bets; check whether this happens without your knowledge and whether the old seed stays visible in the history. If it does not, the ability to verify disappears. Background on random number generators is in the freespin.ee glossary. You can find the link to the provably fair mechanism and the client seed under those terms. The verification guide is here. The technical side of hashing: NIST: FIPS 180-4 and Wikipedia: Commitment scheme.