How do I verify that a random number is fair?

Save the clientSeed and serverHash returned with your outcome. Paste them into the form on this page (or visit the outcome's shortId permalink). The verifier checks the hash against the original record on Provable.io and tells you whether the outcome is genuine.

What is a provably fair outcome?

A provably fair outcome is a random result that is cryptographically tied to a server-side commitment made before the result was known. Anyone in possession of the commitment and the client seed can independently re-derive the outcome and confirm it has not been tampered with.

Verify a Provably Fair Random Outcome

or paste seed & hash

What does "verified" mean here?

If you click Check this outcome and see a green Verified badge, it means the serverHash you pasted matches the hash that Provable.io committed to before generating the random outcome for that clientSeed. We cannot change a past serverHash after it has been issued — so a match is cryptographic proof that the outcome you have in hand is the one we actually produced.

How verification works

Every Provable.io response carries three things you need to keep: a clientSeed (your input), a serverHash (our pre-commitment), and a shortId (a permalink to the outcome). When you submit those values here, the verifier:

Looks up the original seed state we stored for your clientSeed.
Confirms the serverHash you pasted is the one we committed to before generating any outcome for that seed.
Returns the list of outcomes that share that seed/hash pair, so you can share a permalink to the exact one in question.

Want to verify without trusting our server? Use the open-source @provableio/provable-core library — it reproduces the exact byte stream from a clientSeed + revealed serverSeed. For day-scale auditing, the /transparency page lets you check inclusion proofs against the daily Merkle root.

A deeper explainer — HMAC-SHA512 mixing, commit-reveal, Merkle roots, signed webhooks — lives at /security →

Where do I find these values?

Every response from /api/floats, /api/ints, /api/dice, and other RNG endpoints includes clientSeed, serverHash, and a shortId. Save them when you make the request — they are the receipt. Account holders can also browse outcomes on the dashboard and copy the values directly.

If you only have the shortId, paste it into a URL like https://provable.io/o/<shortId> to land on the outcome's permalink page.

Don't have a shortId? Browse the recently shared outcomes wall → for real examples you can click straight through to.