> ## Documentation Index
> Fetch the complete documentation index at: https://docs.kraken.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Heartbeat

> Subscribe to heartbeat messages at timed intervals

<div className="api-banner">
  <span className="api-protocol ws">WSS</span>
  <span className="api-detail">futures.kraken.com/ws/v1</span>
  <span className="api-tag">heartbeat</span>
</div>

The `heartbeat` feed publishes a heartbeat message at timed intervals.

***

## Request

<ResponseField name="event" type="string" required>
  `subscribe` or `unsubscribe`
</ResponseField>

<ResponseField name="feed" type="string" required>
  The requested subscription feed. Value: `heartbeat`
</ResponseField>

<CodeGroup>
  ```json Example theme={null}
  {
    "event": "subscribe",
    "feed": "heartbeat"
  }
  ```
</CodeGroup>

***

## Response Success

<ResponseField name="event" type="string">
  <span className="field-attr">One of:</span> `subscribed`, `subscribed_failed`, `unsubscribed`, `unsubscribed_failed`

  The result.
</ResponseField>

<ResponseField name="feed" type="string">
  The requested subscription feed. Value: `heartbeat`
</ResponseField>

<CodeGroup>
  ```json Example theme={null}
  {
    "event": "subscribed",
    "feed": "heartbeat"
  }
  ```
</CodeGroup>

***

## Response Snapshot

<ResponseField name="feed" type="string">
  The subscribed feed.
</ResponseField>

<ResponseField name="time" type="positive integer">
  The UTC time of the server in milliseconds.
</ResponseField>

<CodeGroup>
  ```json Example theme={null}
  {
    "feed": "heartbeat",
    "time": 1534262350627
  }
  ```
</CodeGroup>

***

## Response Error

<ResponseField name="event" type="string">
  Value: `error`
</ResponseField>

<ResponseField name="message" type="string">
  <span className="field-attr">One of:</span> `Invalid feed`, `Json Error`

  An error message.
</ResponseField>

<CodeGroup>
  ```json Example theme={null}
  {
    "event": "error",
    "message": "Json Error"
  }
  ```
</CodeGroup>