Overview - Delphi Markets API

The Delphi Markets WebSocket API provides real-time streaming for price updates, orderbook snapshots, and trade executions across all supported exchanges.

Supported streams

Kalshi

Subscribe using klsi_id. Prices, orderbook (101-level depth), and trades.

Polymarket

Subscribe using condition_id. Prices, orderbook, and trades.

Predict.fun

Subscribe using market_id. Prices, orderbook, and trades.

Limitless

Subscribe using market_id. Prices, orderbook, and trades.

Gemini

Subscribe using market_id. Prices, orderbook, and trades.

Manifold

Subscribe using market_id. Prices, orderbook, and trades.

Opinion

Subscribe using market_id. Prices, orderbook, and trades.

ForecastEx

Subscribe using market_id. Prices and trades (no orderbook).

PredictIt

Subscribe using market_id. Prices only.

Parlays

Subscribe using market_ids. RFQ events and MVE trades. Requires Pro+ plan.

How it works

Connect to the WebSocket endpoint for your exchange
Subscribe by sending a JSON message with market IDs and message types
Receive real-time updates as JSON messages
Unsubscribe or disconnect when done

Common connection details

All WebSocket streams share these properties:

Property	Value
Protocol	WebSocket (wss://)
Authentication	API key via `api_key` query parameter
Keepalive	Ping every 54 seconds
Timeout	60 seconds without pong
Default message types	Prices and orderbook

Subscription key reference

Exchange	Endpoint	Subscription key	Message types
Kalshi	`/ws/kalshi`	`klsi_ids`	prices, orderbook, trades
Polymarket	`/ws/poly`	`condition_ids`	prices, orderbook, trades
Predict.fun	`/ws/pfun`	`market_ids`	prices, orderbook, trades
Limitless	`/ws/limitless`	`market_ids`	prices, orderbook, trades
Gemini	`/ws/gemi`	`market_ids`	prices, orderbook, trades
Manifold	`/ws/mani`	`market_ids`	prices, orderbook, trades
Opinion	`/ws/opnm`	`market_ids`	prices, orderbook, trades
ForecastEx	`/ws/fex`	`market_ids`	prices, trades
PredictIt	`/ws/prdi`	`market_ids`	prices
Parlays	`/ws/parlays`	`market_ids`	rfq, mve_trades

Quick start

const ws = new WebSocket("wss://api.delphimarkets.com/ws/kalshi?api_key=YOUR_API_KEY");

ws.onopen = () => {
  ws.send(JSON.stringify({
    action: "subscribe",
    klsi_ids: ["KXBTCD-25FEB14-B55000"],
    message_types: ["prices", "orderbook", "trades"]
  }));
};

ws.onmessage = (event) => {
  const data = JSON.parse(event.data);
  console.log(data);
};

See the individual stream pages for complete subscription fields, message schemas, and examples.