Provably Fair Checker

18+ · Gambling can be addictive. The house edge means you lose over time.

How to use it

1. Pick the game and open "Where to find your seeds" for that site's steps. On Stake, rotate your seed pair so the old server seed is revealed.
2. Paste the server seed, your client seed (or public seed) and the nonce or round of the bet.
3. Add the result the site showed, and the server seed hash it showed before you bet.
4. Press Verify: you get a match or mismatch and a hash check. Tick the box to check 20 bets in a row.
5. For a site or game not in the list, use the step by step tab; for crash, the hash chain tab.

Sites this checker covers

A Stake dice bet, worked by hand

The published test case: server seed "server seed", client seed "client seed", nonce 1. This is what the checker does with it.

1. HMAC-SHA256 with the server seed as key and "client seed:1:0" as message gives bf27f216a44fb12d42a468efe880471991877549e22ea9c0abaad93ba53603d4.
2. The first 4 bytes are 191, 39, 242, 22. As a number between 0 and 1: 191/256^1 + 39/256^2 + 242/256^3 + 22/256^4 = 0.74670327.
3. Dice multiplies that by 10,001 and divides by 100, cut to two decimals: 74.67.
4. The commitment: the SHA-256 of "server seed" is a4e53dc2f480b8fce6fe688b1317658b446299df23ad533394406427c8c19557. If that is the hash the site showed before the bet, the seed wasn't changed afterwards.

Which games it checks

Only algorithms the sites publish, and only ones we could test against a published worked example (the button above fills one in, so you can see the verifier give the known answer).

• Stake: Dice. Roll = first float x 10001 / 100, shown to two decimals (0.00 to 100.00).
• Stake: Limbo. Result = 0.99 x 1e8 / (floor(float x 1e8) + 1), cut to two decimals, at least 1.00x.
• Stake: Mines. 24 floats shuffle the 25 tiles; the first ones picked are the mines. Tiles count left to right, top to bottom.
• Stake: Plinko. One float per row: under 0.5 the ball goes left, otherwise right.
• Stake: Keno. 10 floats draw 10 of the 40 numbers, each from the numbers still left.
• CSGOEmpire: Roulette. SHA-256 of server seed-public seed-round; the first 8 hex characters mod 15 give the roll: 0 Dice (14x), 1-7 T, 8-14 CT.
• CSGORoll: Roll (roulette). HMAC-SHA256 keyed with ROULETTE-serverSeed-clientSeed-nonce; the first 13 hex characters / 2^52 x 15 give the roll: 0 green, 1-7 red, 8-14 black, 4 and 11 are also bait.

Stake makes every result from the same stream: HMAC-SHA256 with the server seed as key and "clientSeed:nonce:round" as message, each 4 bytes turned into a number between 0 and 1. Gamdom and Roobet publish their roulette code as well, but without a worked example to test against, so we don't offer them as games yet. Case openings and case battles aren't covered yet.

How the crash hash chain check works

Crash rounds don't use your seeds. The site generates a chain of hashes, each made by hashing the one before (on Stake, the SHA-256 of the previous hash written as hex text), publishes the last one, then plays the chain from the end. So hashing a game's hash gives the game before it, and hashing on reaches the published hash. The crash point mixes in a salt the site couldn't know when it made the chain: Stake uses the hash of a Bitcoin block that hadn't been mined yet when it posted the chain.

• Stake: Crash (chain posted 8 Jul 2019). Salt and last hash from Stake's Crash seeding post of 8 Jul 2019 (a chain of 10,000,000 games). A game from a newer chain won't reach this hash, and its crash points here would be wrong. Formula: HMAC-SHA256 with the game hash as key and the hash of Bitcoin block 584,500 as message; the first 8 hex characters as a number (int); crash point = 2^32 / (int + 1) x 0.99, at least 1.00x. Shown cut to two decimals.
• Stake: Slide (chain posted 20 May 2020). Salt and last hash from Stake's Slide seeding post of 20 May 2020 (a chain of 10,000,000 games). A game from a newer chain won't reach this hash, and its results here would be wrong. Formula: as Stake Crash, with the hash of Bitcoin block 631,111 as message and x 0.98. Shown cut to two decimals.
• CSGORoll: Crash (games before #6788734). HMAC-SHA256 keyed with the game hash and no message. h = the first 13 hex characters as a number: (100 x 2^52 - h) / (2^52 - h) x (1 - 0.0666), at least 100, rounded down, divided by 100 (the script sets its house edge to 6.66). Games from #6788734 use an EOS block per game instead of this chain.

Stake's seeding posts give the chain's last hash, the salt and the formula but no worked example, so we checked our version against Stake's own code run as published (same crash point for every hash we tried). The Stake presets cover those two chains only: Stake's game events page still linked the 2019 Crash post in July 2025 and we found no later seeding post, but a game from a newer chain won't reach the preset's last hash. CSGORoll's script comes with an example hash that gives 2.11x, which the "Fill in" button uses; that hash isn't from the live chain, so it doesn't lead to the first game hash. For any other site, the custom chain option walks the chain with the rule you pick (hash of the hex text or of the raw bytes) and shows no crash points, because we only add a formula a site publishes.

Sources: Stake's game events page (July 2025 copy) links its Crash seeding post (8 Jul 2019, Bitcoin block 584,500) and Slide seeding post (20 May 2020, block 631,111); block hashes checked on blockstream.info; CSGORoll provably fair and its old crash script (checked 25 Oct 2026).

Sources: Stake implementation, conversions and game events; Stake test cases from the open-source fair library; CSGOEmpire: how is roulette fair; CSGORoll provably fair and the Roll verifier script it links (checked 24 Oct 2026).

Checking a Betrefs free case roll?

This part is only for our own free case: every roll can be checked. We commit to a secret server seed before you open, you control the client seed, and anyone can recompute the result.

Verify a free case roll

Ticket ranges

Server seeds

Looking for sites that let you check every bet? See our provably fair gambling sites.

FAQ

How do I check if a bet was provably fair?

Rotate your seed pair on the site so the old server seed is revealed (on CSGOEmpire and CSGORoll roulette the seeds are shared and published for everyone). Copy it with your client seed and the bet's nonce into the checker, pick the game, add the result the site showed and press Verify. Then check that the SHA-256 of the server seed matches the hash the site showed before you bet.

My result doesn't match, what now?

Most mismatches are input mistakes: a nonce off by one (the checker tries the nonce either side for you), a server seed from a different seed pair than the bet, a space copied at the end of a seed, or different game settings such as the mines count or plinko rows and risk. If it still doesn't match with the seeds and nonce the site shows for that bet, send those to the site's support and ask them to explain.

Are my seeds sent anywhere?

No. The check runs in your browser with Web Crypto. Seeds aren't sent to our server and aren't put in the page address; only the game and its settings are, so you can share those.

How do I verify a crash game?

Open the crash hash chain tab and paste the game's hash, which the site shows once the game has ended. The checker lists the games before it (hashing a game's hash gives the one before it) with their crash points, and hashes back until it reaches the chain's last hash that the site published before the games were played. Crash points are only worked out for Stake Crash, Stake Slide and CSGORoll's older crash, the ones whose formula the site publishes.

Can I check a site that isn't listed?

Yes, if the site publishes its algorithm. Use the step by step tab: pick the hash (HMAC-SHA256 with the server seed as key is the most common), type the message the way the site's fairness page writes it, for example {client}:{nonce}, and compare the hash, the floats and the result with what the site shows at each step.

Does provably fair mean I'll win?

No. It proves a result wasn't changed after the seeds were fixed, not that the odds are good. Every game still has a house edge, which you can work out with our house edge calculator.

What is a nonce in provably fair?

A counter that goes up by one with every bet you make on the same seed pair, so each bet gets a different result from the same seeds. On CSGOEmpire roulette the round ID plays that role.

Can a provably fair site still cheat?

It can't change a result once the server seed hash is shown, which is what the check proves. It doesn't tell you the house edge is fair, that a site pays out, or that the game shown matches the published algorithm unless you verify your own bets.

Why can't I verify my current seed?

The server seed stays secret while you're using it; you only see its hash. That's what stops you predicting results. Rotate to a new seed pair and the old one is revealed, then every bet made with it can be checked.

Do mines or crash predictors work?

No. Results come from a server seed that stays secret until after the bets it decides, so nothing outside the site can see the next result. Tools that ask for your login or seeds to predict results are scams.

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