How Provably Fair Gambling Works: A Complete Guide
Learn how provably fair technology uses cryptographic algorithms to let you check game results on games that support it. Understand seeds, hashes and verification.
What Is Provably Fair Gambling?
Provably fair is a technology that uses cryptographic algorithms to show that a game outcome was not changed after you placed your bet. It is available on many crypto-native games, though not on every game a crypto casino offers.
How It Works
The system uses three key components:
- Server Seed: a random value generated by the casino before each bet
- Client Seed: a random value you provide (or that is generated for you)
- Nonce: a counter that increments with each bet
These three values are combined using a cryptographic hash function (usually SHA-256) to determine the game result.
Step-by-Step Verification
- Before you bet, the casino generates a server seed and shows you its hash (a fingerprint of that seed)
- You place your bet with your client seed
- The game result is calculated from both seeds and the nonce
- After the bet, you can see the unhashed server seed
- You can independently check that the hash matches, which shows the result was not changed
Why It Matters
Traditional online casinos ask you to trust that their random number generators (RNGs) are fair. On games that support provably fair verification, you can check each result yourself instead.
Which Casinos Offer Provably Fair Games?
These operators we review list provably fair games:
- BC.Game: BC Originals use a SHA-256 hash chain with provably fair verification
- Stake: Stake Originals use provably fair verification
- Thrill: Thrill Originals are provably fair
- Cloudbet: arcade games use provably fair verification
Not every title on these sites is provably fair, so check the game's own fairness page before relying on it.
Verification Tools
Casinos that offer provably fair games usually provide a built-in verification tool. You can also use third-party verification tools: enter the server seed, client seed and nonce to recalculate the result.
What About Non-Original Games?
Third-party games from providers like Pragmatic Play, Evolution and Play'n GO usually rely on RNGs tested by independent labs such as iTech Labs, GLI or BMM Testlabs. Those results can't be checked on-chain; the assurance comes from the lab certification and the operator's licence.