What is crash gambling? How a crash game casino works

A crash game casino offers one of the simplest bets in gambling: you stake an amount, a multiplier starts at 1.00x and climbs, and you have to cash out before it stops. The moment it stops is called the bust point or crash point. Cash out at 2.40x and you get 2.4 times your stake back; still be in when it busts at 2.39x and you lose the lot. This guide explains what is really happening behind the rising line, where the house edge sits, how hash-chain fairness works, and which of the casinos we have audited run their own crash game and how much of it you can check.

How a crash round works

Every round follows the same pattern, whatever the brand or the theme (rockets, planes, a line on a chart):

1. Betting window. For a few seconds, players place bets. Many games let you set an automatic cash-out target, for example 1.80x, so the game cashes you out the instant the multiplier reaches it.
2. The climb. The multiplier starts at 1.00x and rises, slowly at first and then faster.
3. Cash-outs. At any point you can press cash out. Your payout is your stake times the multiplier shown at that moment.
4. The bust. The multiplier stops at a value that was fixed before the round began. Anyone still in loses their stake.

The key fact is in step 4. The curve on screen is an animation of a number the casino already knows. It does not react to how many players are still in. In a provably fair crash game the bust point is calculated from a hash that existed before the betting window opened, and you can confirm that after the round.

Most crash games are shared: every player in a round sees the same bust point. That is why crash usually cannot use your personal client seed the way single-player games such as dice or limbo do. Casinos use one of two answers instead: a pre-generated hash chain, or a fresh server seed per round combined with some outside value.

Where the bust point comes from

The most widely published method turns a round hash into a number X between 0 and 1, then applies a formula of this shape:

bust point = 0.99 / (1 - X), with anything below 1.00x set to 1.00x.

BC.Game documents exactly this: it takes the first 13 hexadecimal characters of the hash (52 bits), divides by 2^52 to get X, computes 99 divided by (1 minus X), floors the result at 100, rounds down and divides by 100. Gamba publishes a version built from the first 4 bytes of the round hash with the same 1% structure. Thrill uses 1 / ((1 - float) x 1.01) at an RTP of 0.99.

Because X is uniform, the formula gives a long tail. Most rounds bust early, a few run very far, and there is no ceiling in the formula itself. Casinos set a cap in their terms instead; Cybet, for example, caps its crash multiplier at 1,000,000x.

The house edge and the instant bust

The 0.99 in the formula is the house edge. If X is below 0.01, then 0.99 / (1 - X) is below 1, and the round is set to 1.00x. That is an instant bust: the round ends at the start and every bet in it loses, whatever cash-out target was set. With a uniform X, that happens in about 1 round in 100.

That 1% share is the whole edge, seen from another side. For any target M, the chance the round reaches it is about 0.99 / M, and the payout is M, so the expected return is 0.99 of your stake at every target:

Low targets win often and pay little. High targets lose often and pay a lot. None of them change the 99%. Cybet uses a different rule for the same purpose: if the round hash is divisible by 101, the round busts at 1.00x, which is about 1 round in 101, and the 13-hex formula applies otherwise.

So no cash-out pattern beats the game, and past rounds tell you nothing. A run of early busts does not make a long round due. Apps that claim otherwise are covered in our crash predictor guide, and the Spribe game is covered in our Aviator predictor guide.

How hash-chain fairness works

A hash chain lets a casino commit to millions of future rounds at once, without revealing any of them:

1. The casino picks a secret starting value and hashes it with SHA-256. It hashes the result again, and again, for a very long time. BC.Game, Gamdom and 500 Casino each state 10 million hashes; Gamba states a chain of 100,000 links.
2. The chain is played backwards. The last hash produced is used for the first round, the one before it for the second round, and so on.
3. The casino publishes the end of the chain, or announces it, before play starts.
4. After each round, the round hash is shown in the history.

SHA-256 only runs one way. From the current round hash, nobody can compute the next one. But anyone can hash a revealed round hash once and get the previous round's hash. If that link holds for every pair of rounds, the results came from a chain that was fixed before anyone bet.

A chain has one gap: the casino built it, so in theory it could make many chains and keep a favourable one. A salt closes that gap. The casino announces in advance that each round hash will be mixed with the hash of a future Bitcoin block, a value nobody knows yet. BC.Game used block 635,380 when it reseeded in June 2020; 500 Casino uses block #811500; Shuffle and Gamba also mix in a Bitcoin block hash. The salt changes the multiplier, not the chain links, so you check the chain with the raw round hashes and the multiplier with the salted calculation.

Check a crash chain with our tool

1. Open the crash game's round history and copy the hashes of two or more consecutive rounds. Use the round hash or game hash, not a salted result value.
2. Open our hash chain check.
3. Paste the hashes one per line, in the order the history shows them. Newest first or oldest first both work, as long as no round is skipped.
4. Run the check. Each pair should pass: the SHA-256 of one hash equals its neighbour.

A pass proves the rounds were drawn from one pre-committed chain. It does not prove the multiplier shown was computed correctly. For that, use the casino's own verifier with the salt it published. If a link fails, check first that you copied consecutive rounds with none missing. For a worked example of both steps, see how BC.Game crash is verified.

Which audited casinos run their own crash game

From our published casino audits, these are the casinos with an in-house crash game, grouped by how much of a round you can check. We take this from each casino's own fairness pages, recorded in its audit.

Chain and formula both published

• BC.Game: 10 million SHA-256 hashes in reverse, a Bitcoin block salt since 2020, the full formula with a worked example, and a verifier on GitHub. Chain links pass our check. BC.Game audit.
• Gamba: a SHA-256 chain of 100,000 links combined with a Bitcoin block hash as hash seed:nonce:0, and a published crash formula with a 1% edge. Gamba audit.
• 500 Casino: 10 million hashes in reverse, salted with Bitcoin block #811500, with published code and the first ten rounds marked as test rounds. 500 Casino audit.
• Goated: a hash chain from a terminal seed, with crash code on its implementation page. Goated audit.
• Shuffle: a backward SHA-256 chain anchored to a future Bitcoin block hash, with the float to outcome step in its game events article. Its help centre states no crash edge. Shuffle audit.

Chain stated, details thinner

• Gamdom: a 10 million hash chain with the final hash published, but no crash result code in its originals article, so only the links can be checked. Gamdom audit.
• Stake: our record lists Crash and Slide as hash-chain games, but Stake's implementation page sits behind a bot check our reader could not pass, so we have not re-read the formula. Stake audit.

Per-round seed instead of a chain

• Thrill: a new server seed per event, its hash shared at the start and the seed revealed at the close, with the client seed taken from the bet with the highest stake and HMAC-SHA512 over the two. Our chain check does not apply. Thrill audit.
• Cybet: HMAC-SHA256 of the server seed over a fixed public salt, with the 1 in 101 instant bust above. Use Cybet's own verification tab. Cybet audit.

Commitment shown, crash mapping not published

BetFury, Cashy, Chips.gg, Duelbits, Grailbet, MetaWin and Wild.io all list a crash game among their originals and show a hash or seeds, but none publishes the formula from hash to bust point on the pages we read. Grailbet shows the seeds and verification inside each game, and Chips.gg points to its own validator. You can confirm a commitment, but not recompute a bust point independently. Each audit is linked from our fairness index.

What a fair crash game does not promise

Provable fairness answers one question: was the result fixed before you bet? It does not lower the house edge, it does not cap how fast you can lose in a game with rounds every few seconds, and it says nothing about whether a casino pays out. For that, read the payout section of each audit. Set a deposit limit before you play, and treat auto cash-out as a way to control your bets, not as a strategy.

Sources

• BC.Game help centre: Crash, ensuring fair play
• BC.Game crash verification script (GitHub)
• BC.Game on Bitcointalk: crash reseeding event, June 2020
• Gamdom help centre: Gamdom Originals
• Shuffle help centre: provably fair game events
• Thrill help centre: provably fair game event
• Gamba help centre: what is provably fair
• NIST FIPS 180-4: Secure Hash Standard