Provably Fair
Every 155.io round is decided by a seed committed before betting closes — and anyone can reproduce it
Every game on 155.io is provably fair: the outcome of each round is fixed by a secret seed that is committed before betting closes and revealed after the round settles. Anyone — the player, you, or an independent auditor — can take the revealed seed and recompute the exact outcome, with no trust in 155.io required.
The verifier is open source and runs entirely in the player's browser. We publish the algorithm, the test vectors, and the tool; you can host your own copy if you like.
Open the verifier
The public, in-browser round verifier
Source on GitHub
marbles-io/155-fairness-verifier — algorithm, vectors, tests
Verify a round
Step-by-step: from a settled round to a green check
How it works
The hash chain, the draw, and what is (and isn't) proven
What a player can prove
For any settled round, without trusting us:
- The outcome was fixed before betting closed. The seed is committed (as its SHA-256 fingerprint) at round open; the outcome is a deterministic function of that seed. We cannot change it after seeing where the money went.
- The outcome was drawn fairly. The reveal contains everything needed to recompute the result from the seed and confirm it matches what was paid.
- Nothing was cherry-picked. Each round's seed is one link in a pre-committed hash chain with a published root. Seeds are consumed strictly in order, so we cannot mint a favourable seed after the fact.
- The odds are real. For games with weighted options, the exact probabilities are published in each reveal, and the draw provably uses them — so a "40% option" genuinely hits 40% of the time, round after round, verifiably. See what's proven.
Three ways to verify
In-game
Every past round opens a fairness panel showing the commitment, the revealed seed, and a live re-computation.
Support lookup
support.marbles.xyz looks up any round by ID and shows the same fairness card, with a one-click hand-off to the verifier.
Standalone verifier
Paste a round's values (or follow a deep link) into the open-source tool — it recomputes everything client-side.
Covered games
The same commitment-and-reveal scheme runs across all three game families — only the final result mapping differs:
| Family | Games | What the seed decides |
|---|---|---|
| Crash | Footfall | The multiplier curve's crash point |
| Counting (CCTV) | Rush Hour, Snow Run, Duck River | The winning market (Under / Range / Over / Exact) and its boundaries |
| Classic | Plinko, Snake, Rolling Dunes, Coin Flip, Fast Lane, Stairpong, Survivor, Fish Tank | The winner (and the full finishing order for the podium games) |
No integration work for operators
Provable fairness is handled entirely inside the 155.io platform. There are no extra endpoints to implement and nothing to compute on your side. This page exists so you — and your players — can understand and independently check it.