Crash at Gamdom

What Gamdom publishes about Crash

Crash is one of Gamdom's in-house Originals: "place your bet and watch the multiplier rise in real time", and cash out before it stops (help centre, Gamdom Originals, 12 Nov 2026). Rounds are shared, so one crash point applies to every bet. Gamdom's Crash page states the price as "100% for the first $5,000 in wagers, then 99% thereafter, giving a house edge of 1% beyond the Zero Edge limit" (1 Nov 2026). The fairness page links sample code that contains the actual formula, and the two do not say quite the same thing. This page sets them side by side.

The formula in Gamdom's sample code

The fairness page says "The sample code to generate games hashes and calculate Crash results can be found here". The calculation in that code is short:

hash = HMAC-SHA256(key = round hash, message = salt)
if hash is divisible by 100:   crash point = 1.00
otherwise:   h = first 13 hex characters of hash (52 bits),   e = 2⁵²
  crash point = floor( ((e − h / 50) / (e − h)) × 100 ) / 100

Two things in it set the price. The first line of the rule sends one round in 100 straight to 1.00x. The second contains h / 50, and that term matters more than it looks. Writing X for h divided by e, a number spread evenly between 0 and 1, the crash point is (1 − X/50) / (1 − X), and it reaches a target t when X is at least (t − 1) / (t − 0.02). The chance of that is 0.98 / (t − 0.02). A formula with no built-in margin would have 1/t there.

Combining both steps, a round reaches a target t with probability 0.99 × 0.98 / (t − 0.02).

What that returns at each target

Arithmetic from Gamdom’s Crash sample code, 12 Nov 2026, and from the earlier version it links for "game results before 02.01.2026". The last column adds 1% of the stake to the current formula’s return.

By the current sample code the return depends on where you cash out. It is 98.98% at the lowest target of 1.01x, 98.00% at 2x and 97.21% at 10x, and it approaches 97.02% at very high targets. The stated 99% and the formula agree only at the bottom of the range. At a 2x target the code implies a cost of $2.00 per $100 wagered, twice the stated figure; at 10x and above, nearly three times.

The fifth column comes from the sample code's own history. The current code carries the note "For game results before 02.01.2026 see" with a link to the version it replaced. That earlier version has the same formula with one difference: its instant-crash test is divisible(hash, 947), under the comment "In 1 of 1000 games the game crashes instantly", where the current one has divisible(hash, 100). The instant crash therefore went from about 1 round in 947 to 1 round in 100 for results from 2 January 2026, which lowers the return by roughly 0.9 percentage points at every target.

The last column addresses the Zero Edge claim. Gamdom's help centre describes the daily allowance as "a 1% value returned to you through Instant Rakeback" on the first $5,000 wagered on Originals. If the rebate is 1% of the amount wagered, it lifts a 2x cash-out to 99.00% and a 10x cash-out to 98.21% while the allowance lasts. By the sample code it reaches 100% only at the very lowest targets.

We report these as arithmetic from Gamdom's published code. If Gamdom's live game uses a different formula from the sample it links, the figures would differ, and in that case the sample code would not verify real rounds.

The chain, the salt and the commitment

Gamdom's fairness page describes the scheme: "We have generated a chain of 10 million SHA256 hashes for each game, starting with a server secret that has been repeatedly fed the output of SHA256 back into itself 10 million times", and the server "is playing through this chain of hashes in reverse order". Each round's hash is the SHA-256 of the hash of the round played after it. There is no player seed in Crash.

The salt mixed into every round is hard-coded in the sample: 000000000000000007a9a31ff7f07463d91af6b5454241d5faf282e5e0fe1b3a. That is the hash of Bitcoin block 339,300, mined on 17 January 2015. A salt taken from a block that already existed does not add protection in the way a block mined after the commitment does, as on Stake, Shuffle and Roobet; with a known salt, the guarantee rests on the chain's end hash having been published before the rounds were played.

That end hash is on the fairness page. On 12 Nov 2026 it read: "The SHA256 of the final hash for Crash starting at game 12,152,253 is: 965d3f983cc3616c6e9504c79214d73a20db88b1d8eb04f8dbd02b3b54e50533". On 1 Nov 2026 the same line named a chain "starting at game 5,257,547" with a different value. The line is replaced when a new chain starts, so the copy that protects you is the one you saved before your session.

Verifying a round

1. Copy the hash of a finished round. Gamdom: "We're publishing a game's hash immediately after the game ends."
2. Open the Crash sample code from the fairness page and paste the hash into "First hash". It lists the crash point for that round and the rounds before it, each found by hashing the one after.
3. Compare the list with the game's history. For rounds before 2 January 2026 or before 19 November 2025, follow the links in the sample to the older versions.
4. Check the commitment: hashing back from any round should eventually reach the value you saved from the fairness page.

Gamdom's own summary of the method is accurate as far as it goes: "By checking that the SHA256 hash of that game's hash is the game's hash of the previous game you can make sure that we were not able to modify the result." It shows results were fixed in advance. It says nothing about the price, which is in the formula.

Our Crash verifier implements the Stake and BC.Game formulas and has no Gamdom mode, so it should not be used for Gamdom rounds; the sample code on Gamdom's fairness page is the tool for this game. Background: what provably fair gambling proves and the general verifier.

Limits, bonuses and rakeback

The help centre's limits article sets the minimum Originals bet at $0.01 and lists "Crash - $500,000" under maximum bets. The Crash game page caps the profit from a single bet at $500,000. A stake large enough to matter to either limit should be checked against the bet panel.

Three reward rules touch Crash directly, all from the help centre:

• Deposit bonus. "Originals and a few other titles are excluded" from bonus wagering, so Crash bets do not clear a deposit bonus, and "Rakeback isn't generated while the wagering requirement is active".
• King of the Hill. "The first $5,000 wagered across any in-house games won't count toward KOTH points."
• Rakeback. Instant, weekly and monthly rewards depend on bet size, RTP and house edge, and "the exact formula for our rewards is not shared publicly".

The Gamdom promo code page covers the introductory rakeback boost and its six-hour activation window.

Gamdom Crash against Stake, Shuffle and Roobet

Stake: BitcoinTalk seeding post (read 12 Nov 2026), help centre 12 Nov 2026. Shuffle: help centre and game page, 12 Nov 2026. Roobet: verifier and seeding post, 12 Nov 2026. Returns are arithmetic from each published formula.

By its own sample code Gamdom's Crash sits between Stake's and Roobet's on price: dearer than the 1% games at every target above the minimum, and far cheaper than Roobet's. Inside the daily Zero Edge allowance, if the rebate is 1% of wagers, it is the cheapest of the four at low targets. Its commitment is the least durable of the four, because it lives on a page that changes.

Sources: Gamdom fairness page (12 Nov 2026, and as of 1 Nov 2026); Crash sample code and the earlier version it links (12 Nov 2026); Gamdom help centre, Gamdom Originals, minimum and maximum bet amounts, King of the Hill and Deposit Bonus Guide (12 Nov 2026); Gamdom Crash game page (1 Nov 2026); Bitcoin block 339,300. Probabilities and returns are our arithmetic from the sample code.

The auto cash-out calculator shows hit rates for any target. Licence, KYC and withdrawal terms are in the Gamdom review.

Frequently asked questions

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