# Provable.io

> Provable.io is a free, open-source HTTP API for cryptographically verifiable random number generation. Every outcome ships with a `serverHash` (SHA-256 commitment to a server seed) that anyone can independently verify after the fact — no trust in our server required.

Provable.io is operated by RedPkt. The full source of the core RNG library is published at <https://github.com/provableio/provable-core> and the official TypeScript SDK at <https://www.npmjs.com/package/@provableio/sdk>. The site is server-rendered (no JS required to read content) and ships full JSON-LD, OpenAPI, and OG metadata for machine readers.

## Start here

- [Landing page](https://provable.io/): Plain-English intro to provably fair RNG, with live example outcomes.
- [API reference](https://provable.io/api-docs): Every endpoint, parameter, response shape, error code, and runnable example. The authoritative human-readable contract.
- [OpenAPI spec](https://provable.io/openapi.json): Machine-readable contract (OpenAPI 3.1). Generate clients, validators, or fixtures from this directly.
- [llms-full.txt](https://provable.io/llms-full.txt): Long-form version of this file with full prose answers to the questions LLMs are most often asked about Provable.io.

## How it works

- [Security & cryptography](https://provable.io/security): The exact crypto — HMAC-SHA-256 keyed by serverSeed, clientSeed and nonce, mapped to floats via uniform rejection sampling. Includes the threat model and what we don't claim.
- [How provably fair works](https://provable.io/docs/how-provably-fair-works): The commit-reveal model in plain language, with a worked example.
- [Transparency & daily Merkle roots](https://provable.io/transparency): Every day's outcomes are hashed into a Merkle root that's published here, so any single outcome's inclusion can be proved without trusting our database.
- [Verify an outcome](https://provable.io/verify): In-browser verifier. Paste a `shortId` (or `clientSeed` + `serverHash`) and the page re-derives the outcome client-side using WebCrypto.

## Quickstarts

- [curl quickstart](https://provable.io/docs/quickstart-curl): Five-minute, dependency-free quickstart.
- [Node.js quickstart](https://provable.io/docs/quickstart-nodejs): Using `@provableio/sdk` or plain `fetch`.
- [Python quickstart](https://provable.io/docs/quickstart-python): Using `requests` against the raw HTTP API.

## Guides

- [Shuffle a deck](https://provable.io/docs/shuffle-a-deck): Verifiable Fisher–Yates shuffle for cards, raffles, draws.
- [Weighted loot tables](https://provable.io/docs/weighted-loot): Provably fair weighted picks for games and giveaways.
- [Fair raffles](https://provable.io/docs/fair-raffles): Publishable, auditable winner selection for sweepstakes.
- [Dice and coins](https://provable.io/docs/dice-and-coins): NdM dice notation, modifiers, coin flips.
- [NFT trait generation](https://provable.io/docs/nft-trait-generation): Deterministic, auditable trait rolls for collections.
- [A/B test bucketing](https://provable.io/docs/ab-test-buckets): Deterministic experiment assignment with published `serverHash`.
- [Webhooks](https://provable.io/docs/webhooks): Signed delivery, retries, and replay protection.
- [Streaming (SSE)](https://provable.io/docs/streaming): `text/event-stream` with `Last-Event-ID` resume.

## Use-case landing pages

- [Dice Roller API](https://provable.io/use-cases/dice-roller-api)
- [Card Shuffler API](https://provable.io/use-cases/card-shuffler-api)
- [Raffle Picker API](https://provable.io/use-cases/raffle-picker-api)
- [A/B Test Bucketing API](https://provable.io/use-cases/ab-test-bucketing-api)

## Comparisons

- [Provable.io vs Chainlink VRF](https://provable.io/compare/chainlink-vrf): When you don't need randomness inside a smart contract.
- [Provable.io vs Random.org](https://provable.io/compare/random-org): Verifiability vs hardware entropy.
- [Provable.io vs crypto.randomUUID()](https://provable.io/compare/crypto-randomuuid): When local-only random isn't enough.

## Company & legal

- [About](https://provable.io/about)
- [Status](https://provable.io/status)
- [Terms of Service](https://provable.io/terms)
- [Privacy Policy](https://provable.io/privacy)

## Optional

- [Recently shared outcomes](https://provable.io/o): A live wall of the 50 most recent public outcomes, each linked to its permalink and verification page.
- [SDK on GitHub](https://github.com/provableio/provable-core)
- [SDK on npm](https://www.npmjs.com/package/@provableio/sdk)