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Orderbook WebSocket
curl --request GET \
  --url https://synthesis.trade/api/v1/orderbook/ws \
  --header 'Content-Type: application/json' \
  --data '
{
  "type": "<string>",
  "venue": "<string>",
  "markets": [
    "12345",
    "KXBTC-25-T100000"
  ]
}
'
{
  "success": true,
  "response": {
    "orderbooks": [
      {
        "venue": "polymarket",
        "orderbook": {
          "condition_id": "0xbd71b43bb47eb60dbcb41fa25df2a0ed4da612873d6e0447a2c730bd4cc25910",
          "token_id": "21742633143463906290569050155826241533067272736897614950488156847949938836455",
          "bids": {
            "0.61": "1000",
            "0.60": "800"
          },
          "asks": {
            "0.62": "900",
            "0.63": "600"
          },
          "best_bid": "0.61",
          "best_ask": "0.62",
          "hash": "abc123",
          "created_at": "2026-01-01T00:00:00"
        }
      },
      {
        "venue": "kalshi",
        "orderbook": {
          "market_id": "KXBTC-25-T100000",
          "yes": {
            "bids": {
              "58": "25"
            },
            "asks": {
              "60": "15"
            },
            "best_bid": "58",
            "best_ask": "60"
          },
          "no": {
            "bids": {
              "40": "15"
            },
            "asks": {
              "42": "20"
            },
            "best_bid": "40",
            "best_ask": "42"
          },
          "sequence": 12345,
          "created_at": "2026-01-01T00:00:00"
        }
      }
    ]
  }
}

Documentation Index

Fetch the complete documentation index at: https://api.synthesis.trade/docs/llms.txt

Use this file to discover all available pages before exploring further.

Body

application/json
​
type
string
required

WebSocket message type. Supported values: subscribe or unsubscribe.

​
venue
string

Optional venue filter when subscribing without explicit markets. Supported values: polymarket or kalshi.

​
markets
string[]

Optional market list. Maximum 1000 items. Accepts both Polymarket token IDs and Kalshi market IDs. Mixed-venue lists are supported in the same subscribe request.

Example:
["12345", "KXBTC-25-T100000"]

Response

101 - application/json

WebSocket connection established