This verifier recomputes a crash round from its published hash. Paste the revealed game hash and the operator’s salt, and it runs HMAC-SHA256 in your browser, derives the crash point under the 1% formula used by Stake and BC.Game, the bustabit v2 formula or a custom edge, and shows the SHA-256 of the hash for chain checking. Nothing leaves the page. It is for anyone who wants to test a provably fair claim rather than take it on trust.
Provably Fair Crash Verifier
Paste a revealed game hash and reproduce the crash point yourself. Runs entirely in your browser; nothing is sent anywhere.
The operator reveals this after the round ends. Hex only; case and spaces are ignored.
Default is Bitcoin block 584,500, used by Stake and bustabit v2. BC.Game uses its own salt; paste it here if you are checking a BC.Game round.
Applied with the Stake formula: crash = floor(2^52 / (h + 1) x (1 - edge) x 100) / 100.
| Formula | House edge | Crash point | vs zero edge |
|---|---|---|---|
| Stake / BC.Game | 1% | … | … |
| bustabit v2 | ~1% | … | … |
| Custom | … | … | … |
Method: HMAC-SHA256 with the game hash as key and the salt as message, both as UTF-8 text. h is the first 52 bits (13 hex characters) of the digest. Stake style: crash = max(1, floor(2^52 / (h + 1) x (1 - edge) x 100) / 100). bustabit v2: crash = floor((100 x 2^52 - h) / (2^52 - h)) / 100. Some operators use a different salt, a different edge, or instant-bust rules, so always check the formula on the operator's fairness page.
🔢 How to read the results
The main output is the derived crash point. Compare it with the multiplier the game recorded for that round. If they match, the round’s outcome was fixed by that hash and that salt, and no operator input after your bet could have changed it. If they do not match, try the other formula first: the two 1% formulas apply the edge differently and can disagree by a cent or two on the same hash. The verification guide walks through where to find the hash and salt on each site.
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The second output is the SHA-256 of the hash you pasted. In a chained crash game, each game’s hash is the SHA-256 of the next game’s hash: the operator generates a long chain in advance, publishes the final link first, and plays through it backwards. So the SHA-256 of this game’s hash should equal the hash of the previous game. If it does, the round belongs to a sequence that was committed before the round was played. Provably fair explained covers why that ordering matters.
💡 Key insight
A matching crash point proves the outcome was determined by the hash. A matching chain proves the hash was fixed before your bet. Neither proves the salt was chosen without knowledge of the chain, which is why Stake Crash uses a bitcoin block hash mined after the chain was published as its salt, an approach bustabit used first.
📊 The maths behind it
The tool computes HMAC-SHA256 with the game hash as the key and the salt as the message, giving 64 hexadecimal characters. It takes the first 13 characters, which is 52 bits, and reads them as an integer h. Divided by 2^52, that is a number r between 0 and 1. A fair crash game maps r to a multiplier of 1/(1 – r): r = 0.5 gives 2x, r = 0.9 gives 10x, and half of all rounds land below 2x. The edge is then applied. The bustabit v2 formula multiplies the result by 0.99 and rounds down to two decimals with a floor of 1.00x; the formula published by Stake and BC.Game takes its 1% in a different step of the same map, which is why the two can land a cent apart on the same hash. The custom option applies any edge you type as a straight scaling.
Worked example with a sample hash and salt. The HMAC begins 2274c177c92fc, so h = 606,157,718,459,132 and r = 0.1346:
A one-cent disagreement between formulas on the same hash is normal. A disagreement of tens of percent means a wrong hash, a wrong salt, or a game that does not use this scheme.
🎯 What it cannot tell you
It cannot tell you the hash you pasted is the one the operator actually used, so always take it from the game’s own history panel, not from a screenshot or a third-party site. It cannot check games that use a different scheme: Aviator uses SHA-512 with a server seed and three player seeds, and JetX is not cryptographically provably fair at all, so neither will produce a match here. BC.Game Crash and Stake Crash use the formula this tool implements; the provably fair ranking lists which others do.
📝 For the record: The two 1% formulas differ only in how the edge is applied, and the tool follows each operator’s published verification script. If a round matches under neither, the most common cause is a salt with a leading 0x or a trailing space that the operator does not include, or the reverse.
The bottom line: Run the check on a handful of rounds, including the ones that cost you most. A match on every one means the game paid what its own commitment said it would. It does not mean the game is generous: a provably fair game is a game whose 1% edge you can verify, not a game without one.
❓ Frequently asked questions
What if the crash point does not match?
Check the formula dropdown first, then the salt: it must be exactly the string the operator publishes, with no 0x prefix unless the operator includes one. Then confirm the hash is the revealed hash for that round, not the round’s ID or the next round’s hash. A real mismatch after those checks is worth reporting to the operator with the values you used.
Does a match prove the game is fair?
It proves the outcome of that round was fixed by the hash and salt before you bet. Combined with the chain check, it proves the hash was committed in advance. It does not prove the salt was chosen independently of the chain, and it does not change the fact that the formula contains a 1% edge.
Which games use this formula?
Stake Crash, BC.Game Crash and bustabit, and most crypto-casino crash games derived from the bustabit source. Aviator, JetX, Spaceman and the other studio games use their own schemes or none, and this tool will not reproduce their results.
Why is nothing sent to a server?
Because verification only needs the hash, the salt and a hashing function, and every modern browser has SHA-256 built in. Running it locally means no third party sees what you are checking and no third party can alter the result. It also means the tool works offline once the page has loaded.