Free Crash, with the odds of every cash-out
Free Crash, single-player, on a 1,000-game SHA-256 hash chain built in your browser. Watch the curve, cash out before it stops, and read the exact chance of reaching any target below. Play money, no account.
Multiplier over time: it doubles every 2.5 s and stops at the crash point fixed by the game hash. Cash out before it does.
- Public client seed
- plinkolab-crash-public-seed-v1
- Chain head (game 1)
- building…
- Last game hash
- none yet — the head commits to game 1
- Games left in chain
- — of 1000
See the maths
The chain. On your first visit the browser draws 32 random bytes (the terminating seed) and hashes them forward 1000 times with SHA-256. Games are played in reverse: game 1 uses the last hash, game 2 the one before it, and so on. Because SHA-256(hash of game k) = hash of game k−1, the hash you were shown after the previous round is a commitment to the round you are about to play. Nothing can pick a different outcome after the bet.
The result. h = HMAC-SHA256(key = game hash, msg = "plinkolab-crash-public-seed-v1"); X = the first 52 bits of h as a fraction of 252; crash = max(1, floor(99 / (1 − X)) / 100). The 99 is the 1% edge: P(crash ≥ x) ≈ 0.99 / x, so a cash-out at x× pays x and wins 0.99/x of the time, whatever x you choose. About 1 round in 100 crashes at 1.00× instantly.
Check it. Every round shows its game hash. VerifyRoll recomputes the crash point from the game hash and this public client seed, and you can check that SHA-256 of any game hash equals the previous one (any SHA-256 tool will do). Here the client seed is a fixed public string; a casino uses a Bitcoin block hash mined after the chain was published, so that not even the operator could pick a favourable chain.
Play money only. Nothing to buy, nothing to win, nothing leaves your browser. Reset the balance whenever you like.
The chance of reaching any target
Pick an auto cash-out and two numbers follow from one line of arithmetic. P(reach x) = 0.99 ÷ x, and the expected return is x × 0.99 ÷ x = 0.99. A conservative 1.1× and a wild 1,000× are the same bet in expectation; they differ only in how often you get paid.
| Cash out at | P(reach) | Reach, one in | P(miss 10 in a row) | Expected rounds per hit | Expected return |
|---|---|---|---|---|---|
| 1.01× | 98.0% | 1 in 1.0 | 9.3e-16% | 1.0 | 99% |
| 1.10× | 90.0% | 1 in 1.1 | 1.0e-8% | 1.1 | 99% |
| 1.25× | 79.2% | 1 in 1.3 | 0.000015% | 1.3 | 99% |
| 1.50× | 66.0% | 1 in 1.5 | 0.002064% | 1.5 | 99% |
| 2.00× | 49.5% | 1 in 2.0 | 0.11% | 2.0 | 99% |
| 3.00× | 33.0% | 1 in 3.0 | 1.82% | 3.0 | 99% |
| 5.00× | 19.8% | 1 in 5.1 | 11.01% | 5.1 | 99% |
| 10.00× | 9.9% | 1 in 10 | 35.26% | 10.1 | 99% |
| 25.00× | 4.0% | 1 in 25 | 66.76% | 25.3 | 99% |
| 100.00× | 0.990% | 1 in 101 | 90.53% | 101.0 | 99% |
| 1,000.00× | 0.099% | 1 in 1,010 | 99.01% | 1010.1 | 99% |
How Crash works
A chain, not a seed pair. Dice, Plinko and Mines use a server seed, client seed and nonce. Crash uses a chain: chain[i] = SHA-256(chain[i − 1]) from a random terminating seed, 1,000 links long, built in your browser on first visit. Rounds run from the end of the chain backwards, so every round's hash was committed before the previous one was played.
Hash to multiplier. The round's hash is keyed with a fixed public client seed through HMAC-SHA256; the first 52 bits become X in [0, 1), and the crash point is max(1, floor(99 ÷ (1 − X)) ÷ 100). The 99 is the edge: with 100 the distribution would be fair and the instant crashes would vanish.
Cashing out is choosing a threshold. Manual or auto, all a cash-out does is pick the x in 0.99 ÷ x. The Crash strategy guide works through what “cash out at 2×” plus martingale does to a bankroll, with a simulator link that reproduces the run.
Questions
- What are the odds the round reaches 2×?
- 49.5%. The chance of the crash point being at least x is 0.99 ÷ x, so 2× is reached 49.5% of the time, 10× 9.9% and 100× 0.99% (1 in 101). Multiply the chance by the target and every cash-out is worth 0.99 of the stake on average.
- Why does it sometimes crash at 1.00× instantly?
- Because 0.99 ÷ x is capped at 99%: one round in a hundred (2%) crashes before it reaches 1.01×, and nothing cashed out in time. That single percent is where the house edge lives; every other multiplier is priced fairly relative to it.
- How is a free game on a hash chain provably fair?
- On first visit your browser draws a terminating seed and hashes it forward 1,000 times with SHA-256. Rounds are played from the end of the chain backwards, so the hash shown after each round is the SHA-256 of the next round’s hash: a commitment made before the chain was used. The multiplier is HMAC-SHA256(game hash, public client seed) read as 52 bits, then max(1, floor(99 ÷ (1 − X)) ÷ 100).
Keep going
- Crash strategy: what cashing out doesEvery target has the same expectation. What 2× and martingale really do to ruin odds.
- Free DiceCrash at target x is Dice at 99 ÷ x percent. See the same numbers the other way round.
- Strategy simulatorThousands of seeded Crash sessions at any cash-out, with ruin odds and drawdowns.
Last reviewed 2026-09-27