What is Server Seed?

A server seed is the casino's secret input in a provably fair game — a long random string the operator generates for each betting session and uses, together with your client seed and a nonce, to calculate every outcome. Before you bet, the casino shows you only a cryptographic hash (usually SHA-256) of that server seed, not the seed itself. That hash is a public commitment: because a hash cannot be reversed or altered without changing its value, the operator has locked in the exact seed it will use and can no longer swap it for a more favourable one once your results are known. After your session ends, or when you rotate to a new seed, the casino reveals the original server seed. You then hash it yourself and confirm it matches the hash shown earlier, proving the results were predetermined and untampered. Worked example: before playing, a dice site shows the server-seed hash "3a7f...c19b". You set your client seed to "lucky2026" and play 40 bets, the nonce counting 0 to 39. Afterwards the site reveals server seed "e8d2...0f4a". You run SHA-256 on it: if the output equals "3a7f...c19b", the commitment held. Combining that seed with your client seed and each nonce reproduces all 40 rolls exactly, verifying no result was manipulated. For players, the practical takeaway is simple: only trust "provably fair" claims you can actually check, and always verify the revealed server seed against its earlier hash after rotating seeds. Compare with the client seed, the nonce, hash verification and provably fair systems.