api-docs/docs/browser-tracker/markdown/browser-tracker.activitytrackingconfigurationcallback.callback.md
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[Home](./index.md) > [@snowplow/browser-tracker](./browser-tracker.md) > [ActivityTrackingConfigurationCallback](./browser-tracker.activitytrackingconfigurationcallback.md) > [callback](./browser-tracker.activitytrackingconfigurationcallback.callback.md)
## ActivityTrackingConfigurationCallback.callback property
The callback to fire based on heart beat
<b>Signature:</b>
```typescript
callback: ActivityCallback;
```