API Documentation
API access, integration guides, and code examples for all prediction market platforms.
API
APIs & Integrations
Most platforms provide REST APIs and WebSocket for algorithmic trading, data retrieval, and market creation.
8/9
Platforms with API
6/9
WebSocket Support
7/8
No KYC for API
5/9
Open Smart Contracts
Platform API Comparison
| Platform | API Type | Endpoint | Auth | WebSocket | Features |
|---|---|---|---|---|---|
Kalshi | REST + WS | trading-api.kalshi.com | API Key | Yes | Full CRUD, markets/orders/positions |
Polymarket | REST + WS (CLOB) | clob.polymarket.com | Wallet sig | Yes | CLOB, no KYC, USDC |
Rain Protocol | REST + SDK | api.rain.one | Wallet | No | SDK for developers, AI oracle |
Gnosis Omen | GraphQL (The Graph) | api.thegraph.com/gnosis/omen | None | No | Open smart contracts, CTF |
Opinion Labs | REST + WS | api.opinion.trade | Wallet | Yes | Opinion Stack, AI oracle |
Limitless | REST + WS (CLOB) | api.limitless.exchange | Wallet | Yes | CLOB on Base, limit orders |
SX Bet | REST + WS | api.sx.bet | EIP-712 sig | Yes | Market making, parlays, capital efficiency |
// Kalshi REST API — get active markets
const response = await fetch(
'https://trading-api.kalshi.com/trade-api/v2/markets',
{
headers: {
'Authorization': 'Bearer YOUR_API_KEY',
'Content-Type': 'application/json'
}
}
);
const data = await response.json();
// data.markets — array of markets