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Connection

Connect to the Polymarket WebSocket endpoint: 
wss://api.delphiterminal.co/ws/poly
No authentication is required for WebSocket connections.
PropertyValue
ProtocolWebSocket (wss://)
KeepalivePing every 54 seconds
Timeout60 seconds without pong
Max Message Size512 KB

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Subscribing to markets

Once connected, send a JSON message to subscribe using condition_id: 
{
  "action": "subscribe",
  "condition_ids": ["0x00000977017fa72fb6b1908ae694000d3b51f442c2552656b10bdbbfd16ff707"],
  "message_types": ["prices", "orderbook", "trades"]
}
FieldTypeRequiredDescription
actionstringYessubscribe or unsubscribe
condition_idsarrayYesArray of Polymarket condition identifiers (hex strings starting with 0x)
message_typesarrayNo["prices"], ["orderbook"], ["trades"], or any combination. Defaults to prices and orderbook if omitted

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Unsubscribing

{
  "action": "unsubscribe",
  "condition_ids": ["0x00000977017fa72fb6b1908ae694000d3b51f442c2552656b10bdbbfd16ff707"]
}

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Message types

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Price messages

Real-time price updates for subscribed markets: 
{
  "type": "prices",
  "data": {
    "exchange": "poly",
    "condition_id": "0x0000097701...",
    "price": 0.992,
    "last_update": "2026-02-04T15:30:00Z"
  }
}

​
Orderbook messages

Real-time orderbook snapshots for subscribed markets: 
{
  "type": "orderbook",
  "data": {
    "snapshot_time": "2026-02-04T15:30:00Z",
    "exchange": "poly",
    "market_id": "0x1234abcd...",
    "condition_id": "0x0000097701...",
    "bid_side": [0.55, 0.54, 0.53, 0.52, 0.51],
    "ask_side": [0.56, 0.57, 0.58, 0.59, 0.60],
    "original_last_update": "2026-02-04T15:29:59Z"
  }
}

​
Trade messages

Real-time trade executions for subscribed markets: 
{
  "type": "trades",
  "data": {
    "exchange": "poly",
    "condition_id": "0x0000097701...",
    "token_id": "0x123...",
    "market_id": "0xabc...",
    "price": 0.65,
    "size": 100.5,
    "side": "buy",
    "last_update": "2026-02-04T15:30:00Z"
  }
}

​
Full example

const ws = new WebSocket("wss://api.delphiterminal.co/ws/poly");

ws.onopen = () => {
  console.log("Connected to Polymarket WebSocket");

  ws.send(JSON.stringify({
    action: "subscribe",
    condition_ids: ["0x00000977017fa72fb6b1908ae694000d3b51f442c2552656b10bdbbfd16ff707"],
    message_types: ["prices", "orderbook", "trades"]
  }));
};

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

  if (data.type === "prices") {
    console.log("Price update:", data.data);
  } else if (data.type === "orderbook") {
    console.log("Orderbook update:", data.data);
  } else if (data.type === "trades") {
    console.log("Trade:", data.data);
  }
};

ws.onclose = () => console.log("Disconnected");
ws.onerror = (error) => console.error("WebSocket error:", error);

​
Important notes

  • No authentication required for WebSocket connections
  • Use condition_id (Polymarket condition identifier) to subscribe
  • Messages are only sent for markets you have explicitly subscribed to
  • Multiple markets can be subscribed in a single message
  • Trades must be explicitly requested (not included in the default subscription)
  • Orderbook updates are high-frequency — consider filtering client-side if needed