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The heartbeat keeps your session alive. Send a heartbeat with a requestTimeout (in seconds) — if the server does not receive another heartbeat before that timeout elapses, all of your open orders are automatically cancelled. You typically send heartbeats on a recurring interval (e.g. every 5s with a 10s timeout) for the lifetime of your connection.

​
Request

[
  "heartbeat",
  {
    "requestID": "YOUR_REQUEST_ID",
    "requestTimeout": 10
  }
]
​
requestID
string
A client-generated identifier; echoed back on the response. If omitted, the server generates one.
​
requestTimeout
number
required
Number of seconds the server should wait for the next heartbeat before cancelling all of your open orders. Must be greater than 0.

​
Response

The server replies with a heartbeatAck containing the server’s clock and the active timeout. 
{
  "requestID": "YOUR_REQUEST_ID",
  "data": {
    "type": "heartbeatAck",
    "serverTime": "2026-04-22T15:30:00.123456789Z",
    "timeoutSec": 10
  }
}
​
data.type
string
Always heartbeatAck.
​
data.serverTime
string
Current server time as RFC 3339 with nanosecond precision.
​
data.timeoutSec
number
Echoes the requestTimeout you sent.

​
Errors

If requestTimeout is missing or <= 0, the server returns: 
{
  "requestID": "YOUR_REQUEST_ID",
  "error": "Invalid heartbeat timeout"
}