WebSocket Overview

Real-time orderbook and trade streaming via WebSocket

Connection

Connect to the WebSocket endpoint with your API key:

Environment	URL
Local server	ws://localhost:3847/ws
Hosted API	wss://api.pmxt.dev/ws?apiKey=YOUR_KEY

All messages are JSON text frames. A single connection supports multiple concurrent subscriptions.

Protocol

Subscribe

{ "id": "req-1", "action": "subscribe", "exchange": "polymarket", "method": "watchOrderBook", "args": ["OUTCOME_ID", 50] }

Data event

{
  "event": "data",
  "id": "req-1",
  "method": "watchOrderBook",
  "symbol": "OUTCOME_ID",
  "source": "polymarket",
  "data": {
    "bids": [{ "price": 0.42, "size": 100 }],
    "asks": [{ "price": 0.58, "size": 200 }],
    "timestamp": 1778450010713
  }
}

Unsubscribe

{ "id": "req-1", "action": "unsubscribe", "exchange": "polymarket", "method": "watchOrderBook", "args": ["OUTCOME_ID"] }

Error

{ "event": "error", "id": "req-1", "error": { "message": "..." } }