A hash is the output of an algorithm that converts any input into a character string of fixed length. The same input always gives the same hash, but the input cannot be computed back from the hash. Casinos almost always use SHA-256.
Why it is the load-bearing part of the provably fair scheme
The casino generates a server seed and shows you its hash before the game. Since the seed cannot be derived from the hash, you cannot know the result in advance. But since the same seed always gives the same hash, the casino cannot change the seed afterwards either — if it did, the hash of the revealed seed would not match the one it showed you before.
That is the core of the whole provably fair system: committing without disclosing.
How to check
Copy the server seed hash from the game settings before betting. After rotating the seed pair the casino reveals the seed in full. Run it through any SHA-256 calculator and compare the result — they must match character for character. A difference anywhere means something has been changed.
What a hash does NOT prove
Only that an individual round was not faked. It says nothing about the size of the house edge, whether the withdrawal arrives, or the fairness of the bonus terms. See server seed and client seed.
Example: one letter changes everything
SHA-256 turns any input into a 256-bit output, or 64 hexadecimal characters. The text abc gives the hash ba7816bf8f01cfea414140de5dae2223b00361a396177a9cb410ff61f20015ad. Change only the last letter (abd) and the hash is a52d159f262b2c6ddb724a61840befc36eb30c88877a4030b65cbe86298449c9: the outputs do not resemble each other at all. An added line break does the same: abc plus a line break gives edeaaff3f1774ad2888673770c6d64097e391bc362d7d6fb34982ddf0efd18cb. This property is called the Wikipedia: avalanche effect and the SHA-2 family standard is NIST: FIPS 180-4.
Common mistakes when verifying
- A trailing space or line break. Copy the seed without surrounding text and check that the calculator adds nothing.
- The input type. Some games hash the seed as text, some as bytes; find the right variant in the game's verification guide instead of guessing.
- Confusing hashing with encryption. A hash cannot be "decrypted"; it is one-way.
- Confusing a seed phrase with a server seed. A seed phrase is the key to your wallet; it is never entered into any hash calculator, not even during verification. A server seed is a value the game has made public, and hashing it is safe.
What a hash gives and what it does not
A hash binds the casino to one specific seed before the game, but says nothing about how the game result is calculated from the seed. That formula must be public; see the verification guide and check whether the game is the casino's own originals game. For background on random numbers see the freespin.ee glossary.