WebSocket API

Live candle stream

On subscription the stream replays the latest candle of the requested timeframe and then forwards live updates of the forming candle. Historical ranges are not part of this API: use the REST endpoint GET /api/v1/marketdata/candles for history. A terminal upstream error is delivered as an error frame and closes the socket; when the upstream stream ends the socket is closed normally.

Cost: 10 credits per subscription, charged again in every quota window the connection stays open in.

WSS

api

marketdata

candles

stream

Messages

{
  "type": "candle",
  "meta": {
    "exchange": "BATS",
    "symbol": "AAPL",
    "timeframe": "1m"
  },
  "tag": 1,
  "isLast": true,
  "candle": {
    "timestamp": "2026-09-21T19:59:00Z",
    "open": "339.27",
    "high": "339.35",
    "low": "338.93",
    "close": "339.05",
    "volume": "17501",
    "sessionType": "MAINSESSION"
  }
}

x-api-key

type:httpApiKey

API key sent on the WebSocket upgrade request. Exactly one header value is required; duplicate or comma-combined values are rejected.

method

type:string

GET

query

type:object

Candle frame

type:object

The latest replayed candle or a live update of the forming candle.

Error frame

type:object

Terminal error converted from an upstream status; closes the socket.

Messages

{
  "type": "candle",
  "meta": {
    "exchange": "BATS",
    "symbol": "AAPL",
    "timeframe": "1m"
  },
  "tag": 1,
  "isLast": true,
  "candle": {
    "timestamp": "2026-09-21T19:59:00Z",
    "open": "339.27",
    "high": "339.35",
    "low": "338.93",
    "close": "339.05",
    "volume": "17501",
    "sessionType": "MAINSESSION"
  }
}