A provably fair calculator lets you check a casino result after the hidden server seed is revealed. This verifier hashes the server seed, reproduces a transparent HMAC-SHA256 digest from the client seed and nonce, and turns that digest into reference outcomes without sending the seeds anywhere.
How to verify a provably fair bet
Before a bet, the operator publishes a SHA-256 commitment to a secret server seed. Save that hash. After the seed is revealed, enter it here: its SHA-256 hash must match the saved commitment exactly. A mismatch means you are not checking the seed that was committed before play.
Next, copy the client seed and nonce used for the round. This tool calculates HMAC-SHA256 with the server seed as the key and clientSeed:nonce as the message. Compare the digest and each game-conversion step with the operator's published specification.
Crash, Dice, Plinko and Mines
The same digest can be converted in many ways. The reference Dice result maps the first 52 digest bits to 0–99.99. The Crash example applies a 1% edge to the same unit interval. Plinko reads left/right bits, while Mines uses a deterministic 25-cell shuffle.
These outputs demonstrate reproducibility; they are not a universal casino standard. Operators may swap HMAC key/message order, add a cursor or game id, reject biased samples, or use a different house-edge formula. Verification succeeds only when every documented step agrees.
What to do when the result does not match
First confirm exact case, whitespace, nonce and the client seed active for that round. Then confirm whether the site uses SHA-256 or HMAC-SHA256, the order of seeds, delimiters and any cursor. Finally compare the byte-to-number conversion and house edge.
Keep the original commitment, revealed seed, round id and operator specification. A different generic calculator cannot prove manipulation when its algorithm differs; a commitment hash mismatch is the strongest immediate failure.
FAQ
What does provably fair mean?
It means a player can independently reproduce a result from seeds committed before play, so the operator cannot silently choose a new seed after seeing the bet.
Is one provably fair formula universal?
No. Commitment hashes are commonly SHA-256, but HMAC inputs and game conversion rules differ. Always match the operator's published algorithm.
Are my seeds uploaded?
No. Hashing and outcome conversion run locally in your browser.