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CRASH PROVABLY FAIR VERIFIER

Verify any Crash round instantly. Enter your seeds and nonce to recompute the crash multiplier with HMAC-SHA256 and confirm the result was fair — entirely in your browser.

Enter Your Crash Game Details

This page is pre-set to Crash. All presets use the same open-source scheme: HMAC-SHA256(server seed, "clientSeed:nonce:cursor"). Stake and Shuffle are confirmed byte-for-byte; other casinos may differ — see the full verifier.

HMAC-SHA256 Hash
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Game Result

Calculation Breakdown

Crash is the flagship provably-fair game at Stake, Roobet, BC.Game and most crypto casinos: a multiplier climbs from 1.00x and busts at a random point, and your job is to cash out before it does. Because the bust point is generated cryptographically, you can verify after the fact that the casino did not move it. This tool recomputes the exact crash multiplier from your revealed seeds so you can prove any round was fair.

HOW CRASH RESULTS ARE CALCULATED

Modern per-bet Crash (Stake-style) derives the bust multiplier directly from the HMAC-SHA256 hash of your seed pair and nonce:

  1. Compute HMAC-SHA256(serverSeed, "clientSeed:nonce:0") → a 64-character hex hash.
  2. Take the first 8 hex characters and read them as a 32-bit integer.
  3. Apply max(1, floor( (2^32 / (int + 1)) × 0.99 × 100 ) / 100). The 0.99 is the 1% house edge.

Worked example — paste these into the tool to reproduce it: server seed some server seed, client seed some client seed, nonce 1. The first 8 hex chars are 97887987 → integer 2542303623, giving a crash point of 1.67x.

Important: crash formulas are not universal. This is the modern per-bet Stake-style formula. Some operators (bustabit-style) use a pre-generated hash chain instead, so always cross-check the number against your own casino's revealed round.

WHY VERIFY CRASH?

Provably fair only protects you if you actually check it. Verifying a Crash round proves the result was computed from the server seed the casino committed to before your bet, combined with the client seed you chose — so the operator could not have altered the outcome after seeing your wager. Spot-checking even a handful of rounds keeps the system honest and removes any doubt during a losing streak.

Want the full picture? The all-games provably fair verifier handles Crash, Dice, Limbo, Roulette, Mines, Plinko and Keno in one place, and our guide on what provably fair gambling is explains the cryptography from the ground up.

Related Resources

Play Crash: Stake Crash

Strategy: Crash Game Strategy Guide

Compare operators: Best Provably Fair Casinos 2026

CRASH VERIFIER FAQ

No. The server seed is only revealed after you rotate it, and HMAC-SHA256 cannot be reversed, so the next bust point is unknowable. Any "crash predictor", signal bot, or hack promising future multipliers is a scam. This verifier only checks rounds that already happened.
Most often because the operator uses a different crash formula (for example a bustabit-style hash chain rather than the per-bet Stake formula), or because you entered the hashed rather than the revealed server seed, or the wrong nonce. Double-check all three inputs and your casino's documented scheme.
The Stake-style formula bakes in a 1% house edge via the 0.99 multiplier. That means a fraction of rounds instantly bust at 1.00x; over time it gives the house its margin while every individual round stays verifiable.
Aviator is a crash-style game by Spribe with its own provably-fair implementation that combines seeds from multiple players. The math differs from the per-bet Stake formula, so use Aviator's in-game verifier for those rounds.