> For the complete documentation index, see [llms.txt](https://docs.hello-lisa.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.hello-lisa.com/developers/guides/player-communication/message-api-reference/app/app-heartbeat.md).

# App — Heartbeat

The LiSA Player regularly sends a **Heartbeat** to signal its continued availability.

This message is sent by the LiSA Player to the host app / environment.

### Properties

Along with all standard [Message properties](/developers/guides/player-communication/message-api-reference.md#properties), a **Heartbeat** message includes the following additional properties:

<table><thead><tr><th width="239" valign="top">Name</th><th width="162" valign="top">Type</th><th valign="top">Description</th></tr></thead><tbody><tr><td valign="top"><code>messageType</code></td><td valign="top"><pre><code>Literal
</code></pre><p>Required.</p></td><td valign="top"><code>lsc:app:heartbeat</code></td></tr></tbody></table>

#### Legacy Properties

{% hint style="warning" %}
If your integration uses **LiSA Player Version 1**, none of the properties described above will be available.

For **LiSA Player Version 2**, legacy properties can be ignored.
{% endhint %}

<table><thead><tr><th width="239" valign="top">Name</th><th width="162" valign="top">Type</th><th valign="top">Description</th></tr></thead><tbody><tr><td valign="top"><code>action</code></td><td valign="top"><pre><code>Literal
</code></pre><p>Required.</p></td><td valign="top"><code>heartbeat</code><br><br><span data-gb-custom-inline data-tag="emoji" data-code="26a0">⚠️</span> Please use <code>messageType</code> instead.</td></tr><tr><td valign="top">playing</td><td valign="top"><pre><code>Boolean
</code></pre><p>Required.</p></td><td valign="top">The <code>playing</code> property signifies whether media playback is currently in progress.<br><br><span data-gb-custom-inline data-tag="emoji" data-code="26a0">⚠️</span> Please subscribe to <a href="/developers/guides/player-communication/message-api-reference/media/media-progress.md">Media Progress</a> message instead.</td></tr><tr><td valign="top"><code>target</code></td><td valign="top"><pre><code>Literal
</code></pre><p>Required.</p></td><td valign="top"><code>player</code><br><br><span data-gb-custom-inline data-tag="emoji" data-code="26a0">⚠️</span> Please use <code>messageType</code> instead.</td></tr><tr><td valign="top"><code>time</code></td><td valign="top"><pre><code>Number
</code></pre><p>Optional.</p></td><td valign="top"><p>The <code>time</code> property represents the current playback position of the media item, measured in milliseconds from the start.</p><ul><li><strong>For on-demand content</strong> (e.g., replays, stories), this value indicates the exact position the user is watching.</li><li><strong>For live streams</strong>, this value represents the current timestamp relative to the live broadcast</li></ul><p><span data-gb-custom-inline data-tag="emoji" data-code="26a0">⚠️</span> Please subscribe to <a href="/developers/guides/player-communication/message-api-reference/media/media-progress.md">Media Progress</a> message instead.</p></td></tr></tbody></table>

***

### Type Definition

```typescript
interface AppHeartbeatMessage extends Omit<
  Message,
  'messageType' | 'sender'
> {
  messageType: 'lsc:app:heartbeat';
  sender: 'LiSA';
}
```

***

### Examples

```json
{
  "clockDriftInMs": 0,
  "messageType": "lsc:app:heartbeat",
  "sender": "LiSA",
  
  "action": "heartbeat",
  "playing": true,
  "target": "player",
  "time": 620
}
```