APIs for Prediction Markets

Access live and historical orderbook data across Polymarket, Kalshi, Gemini, and more — through a single unified API.

PolymarketKalshiGeminiCoinbaseForecastex

# Historical orderbook
curl -H "x-api-key: $GRAYLAYER_KEY" \
  "http://data.graylayer.tech/api/kalshi/snapshots/KXBTC-25?start_ts=2026-03-26T14:00:00Z&limit=50"
# Live market data via proxy
curl -H "X-API-Key: $GRAYLAYER_KEY" \
  "http://gateway.graylayer.tech/api/v1/polymarket/markets?active=true"

API ResponseLive

{
  "exchange": "kalshi",
  "ticker": "KXBTC-25",
  "count": 4,
  "rows": [
    {
      "ts": "2026-03-26T14:00:01Z",
      "side": "bid",
      "price": "0.4800",
      "quantity": "150.00"
    },
    {
      "ts": "2026-03-26T14:00:01Z",
      "side": "ask",
      "price": "0.5200",
      "quantity": "80.00"
    }
  ]
}

One key, every market

A single x-api-key header unlocks live and historical data across all supported exchanges. No per-platform auth, no rate-limit juggling — just clean JSON responses.

Full orderbook snapshots & deltas
Historical data from March 2026
Live proxy with WebSocket support

Historical Orderbook Data

Access full orderbook history from March 2026 across Kalshi, Gemini, and Polymarket. Snapshots and deltas available for every ticker.

Unified Market Proxy

One API key for Polymarket, Kalshi, Gemini, Coinbase, and Forecastex. The proxy handles auth, rate limiting, and request signing automatically.

Real-Time WebSockets

Stream live orderbook updates, trades, and price changes via WebSocket proxy. No platform auth boilerplate required.

Supported Exchanges

PolymarketKalshiGeminiCoinbaseForecastex

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