Part of the complete guide: Provably fair: the complete guide
What an RNG is
A random number generator is software that produces numbers that look random. Most games, online and offline, use one. A cryptographically secure RNG is seeded with real entropy and is unpredictable in practice. A casino's RNG decides every spin and every card.
What "certified RNG" means
Independent test labs examine a generator and the game's maths, run statistical tests on its output and check that the software in production matches the approved version. The certificate says that, when tested, the game behaved as designed and paid out the stated rate. It is a valuable check, but it is a point-in-time review by a third party, and you rely on the lab and the regulator to enforce it.
What provably fair adds
Provably fair gives the player a way to verify individual results. The operator commits to a secret before you play, mixes in your own input and uses a published formula. Afterwards, you recompute the result and check it matches. You do not need to trust a lab or an operator's claim about a particular bet, though you still trust that the formula is applied honestly across all bets.
Comparison
| Question | Certified RNG | Provably fair |
|---|---|---|
| Who verifies? | A lab, at a point in time | You, on any bet |
| Can a single result be checked? | No | Yes |
| Does it test the house edge and payouts? | Often, yes | No |
| Does it test the software? | Yes | No, only the result calculation |
| Needs a regulator? | Usually part of a licence | No |
| Weakness | Trust in the lab, snapshot in time | Says nothing about odds or payment |
The best case: both
A well-run operator uses a secure RNG, has the maths and payout rates audited, and lets players verify results. Be suspicious of sites with neither, and cautious about sites with only a badge. Look for a link to a real certificate or a documented formula you can test.
Lotteries
For a lottery, there is a stronger option than either: take randomness from a public beacon the operator does not control, publish the ticket list and let anyone recompute the winners. That is how our draws work. See verifiable randomness explained, and read the complete guide to provably fair.
A quick scenario: two sites, one question
Site A shows a "certified RNG" badge from a test lab. Site B publishes its hashed server seed before each session, reveals it afterwards, and documents the formula. You lose a big bet on each. On Site B, you can check that the result followed the committed seed and your own client seed, so a claim that the result was altered after your bet can be tested in a minute. On Site A you can look at the certificate and trust the lab, but you cannot check your own bet. Neither tells you whether you were given fair odds, or whether you will be paid if you win. Combining both is the strongest position, and where possible you should also look at payout rates, licences and track record.
Questions to ask a site that claims either
- 1If "certified": by which lab, when, which version of the software, and is the certificate public?
- 2If "provably fair": where is the formula, do I see the seed hash first, and can I set my own client seed?
- 3What is the house edge or payout share for each game?
- 4How are winnings paid, and how fast?
- 5Who is the operator, and what licence do they hold?
Ready?
A weekly draw you can check yourself.
$5 tickets, a public random value, and every result published with the data to recompute it.
Frequently asked questions
Is provably fair better than RNG?
They are different. Provably fair is player-verifiable per result. A certified RNG is lab-tested. The best sites offer both.
Does provably fair use an RNG?
Yes, in the sense that the output is derived from random seeds. The difference is that you can check it.
Is a certified RNG fair?
It means a lab tested it. It does not let you verify your own result.
Which should I trust?
Neither alone is a guarantee. Prefer verifiable results plus audited payouts and a track record of paying.
Can a certified RNG be provably fair too?
Yes. A site can use a certified generator and also let players verify results with seeds.
Which gives players more control?
Provably fair, because you can verify any result and set your own client seed.
Do regulators require RNG certification?
Licensed jurisdictions generally require certified random number generators and testing.