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One API for every prediction market.
Prices, orderbooks, trades, and history from Polymarket and Kalshi — one integration.
arbiter
Demo
MarketPriceVolume
Will BTC hit $200K by 2026?0.62$1.2M
Fed rate cut before July?0.38$890K
US GDP growth > 3% in Q2?0.71$2.4M
Trump wins 2028 nomination?0.45$5.1M
ETH flips BTC by 2027?0.08$340K
5 markets~47ms
19,000+
Markets tracked
390K+
Trades ingested
1M+
Data points per day
Built for developers
The infrastructure layer for prediction market data.
01
Historical Data
Access historical trades, price charts, and orderbook snapshots across platforms. Backtest strategies and analyze market movements over time.
GET /v1/markets/{id}/candles
{
"market_id": "poly_0x3a75...",
"interval": "1h",
"candles": [
{ "t": 1711324800000, "o": 0.52, "h": 0.58, "l": 0.49, "c": 0.55, "v": 12400 },
{ "t": 1711328400000, "o": 0.55, "h": 0.61, "l": 0.53, "c": 0.60, "v": 8900 },
{ "t": 1711332000000, "o": 0.60, "h": 0.63, "l": 0.57, "c": 0.62, "v": 15200 }
]
}// Install
npm install arbiterapi
import { ArbiterClient } from 'arbiterapi'
const client = new ArbiterClient({
apiKey: process.env.ARBITER_API_KEY
})
// Works for Polymarket and Kalshi
const book = await client.markets.orderbook("poly_0x3a75...")
const candles = await client.markets.candles("kal_BTCUSD", {
interval: "1h",
start: new Date("2026-01-01")
})02
Unified SDK
TypeScript and Python clients with full type safety. One integration for every prediction market.
03
Real-Time Updates
Stream trades, orderbook changes, and price moves via WebSocket. One connection for every platform.
wss://api.arbiterapi.com/v1/ws/trades
streaming
12:34:02.441will-btc-hit-200kbuy0.621250
12:34:01.892fed-rate-cut-julysell0.3841,200
12:34:01.203will-btc-hit-200kbuy0.620500
12:34:00.671us-gdp-growth-q2buy0.7133,000
12:33:59.445fed-rate-cut-julysell0.386800
12:33:58.102eth-flips-btc-2027buy0.081150
AggregatingPolymarket/Kalshi/more coming