Hashed server seed
The SHA-256 hash of the casino's secret server seed, shown before play as a commitment that the seed will not change.
The hashed server seed is the public commitment in a provably fair system. The casino generates a server seed, computes its SHA-256 hash, and shows you that hash before you place any bets with it.
Why it works
SHA-256 is a one-way function. From the hash, nobody can work out the seed, so your future results stay unpredictable. And it is not feasible to find a second seed with the same hash, so the casino cannot swap in a different seed later.
What to record
Copy the hashed server seed when you start a session and keep it somewhere outside the casino, such as a note or screenshot. If the casino later shows a different hash in your history, that is a serious red flag.
Worked example
You note the hash at the start of a session. After rotation, the casino reveals the seed. You compute SHA-256 of the seed in our verifier or any SHA-256 tool. The output must match your note exactly, character for character. If it does not, results from that seed cannot be trusted.