cs2-gambling-toolkit

Open-source verifier and calculators for CS2 (Counter-Strike 2) gambling. Zero dependencies, MIT licensed, runs in Node.js ≥ 20 and every modern browser (WebCrypto).

Hosted versions (no install needed): syntskins.com/tools

| Tool | What it does | Hosted | |---|---|---| | Provably-fair verifier | Checks a site's server-seed commitment (SHA-256) and recomputes rolls from HMAC-SHA256(serverSeed, clientSeed:nonce) | syntskins.com/tools/provably-fair-verifier | | Case EV calculator | Expected value and house edge of a case from its published drop rates | syntskins.com/tools/case-ev-calculator | | Wagering calculator | The real expected cost of clearing a bonus wagering requirement | syntskins.com/tools/wagering-calculator |

Built and maintained by SynTSkins, an independent CS2 gambling site directory. The maths here is the same maths behind our published reviews.

Why this exists

"Provably fair" badges are everywhere in skin gambling; independent verification is not. This toolkit lets you check, with standard cryptography and no trust in anyone's website (including ours):

1. that a site committed to its randomness before you bet — SHA-256(serverSeed) must equal the hash the site published in advance;
2. that each roll follows from the seeds — outcomes derive from HMAC-SHA256(key = serverSeed, message = clientSeed:nonce);
3. what a case or bonus is actually worth — expected value is arithmetic, not marketing.

CLI usage

npx cs2-gambling-toolkit help          # or: node bin/cli.js

# Verify a roll after the site reveals its server seed
cs2-toolkit verify --server-seed "revealed-seed" --client-seed "your-seed" --nonce 42 \
                   --hash "published-sha256-commitment"

# Check a seed commitment on its own
cs2-toolkit hash --server-seed "revealed-seed"

# Expected value of a $10 case (item value : drop probability in %)
cs2-toolkit ev --price 10 --items "400:0.5,45:8,8:25,1.8:66.5"

# Expected cost of clearing a $50 bonus at 35x wagering on 5%-edge games
cs2-toolkit wagering --bonus 50 --multiplier 35 --edge 5

Library usage

import { verifyRoll, caseEv, bonusCost } from 'cs2-gambling-toolkit';

const { hashValid, hmac, outcomes } = await verifyRoll({
  serverSeed: 'revealed-seed',
  serverSeedHash: 'published-commitment',
  clientSeed: 'your-seed',
  nonce: 42,
});
// outcomes.roulette -> { roll: 0-14, color: 'green'|'red'|'black' }
// outcomes.percentRoll -> 0.00-100.00
// outcomes.crash -> multiplier >= 1.00

The formulas (and their limits)

• Commitment: SHA-256(serverSeed) === publishedHash. Universal across sites.
• Roll digest: HMAC-SHA256(key = serverSeed, message = clientSeed + ":" + nonce). Used by the large majority of platforms; a few concatenate differently — check the site's fairness page.
• Roulette (0–14): parseInt(hmac[0..8], 16) % 15, colours 0 = green, 1–7 = red, 8–14 = black.
• Percent roll (0–100.00): parseInt(hmac[0..8], 16) % 10001 / 100.
• Crash: bustabit-style, X = parseInt(hmac[0..13], 16) / 2^52, multiplier = max(1.00, floor((100 − edge%) / (1 − X)) / 100).

Two honest caveats. First, outcome derivations vary by site — the digest step is standard, the mapping to a game result is not, so always compare against the formula the site documents. Second, provably fair proves the roll wasn't manipulated; it does not prove the odds are good, the item pricing is honest, or that you'll get paid. See our guides: what provably fair actually means and case odds & expected value.

Development

npm test   # node --test, 14 tests, no dependencies

Disclaimer

For education and verification. Gambling involves risk and is age-restricted (18+, 21+ in some jurisdictions). If gambling has stopped being entertainment, start here instead: responsible gambling resources.

License

MIT © 2026 SynTSkins