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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" } } ] } }

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 5000 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