# Hackle Event (Auto-collected)

Events whose Event Key starts with `$` are events managed separately by Hackle.

## 1. Auto-collected Events

{% hint style="info" %}
Auto-collected events are only collected by Web / App SDKs.
{% endhint %}

In the \[Auto-collected Events] section of Event Management, you can view events that are automatically collected without separately sending events.

![Event Management > Auto-collected Events](/files/Ielh5L3iUSPJByyTW7lN)

<table data-full-width="true"><thead><tr><th width="157.93359375">Event Key</th><th width="396.88671875">Description</th><th width="79.78125">Web</th><th width="76.4296875">App</th><th width="73.90625">Billing</th><th width="90.53125">on/off</th></tr></thead><tbody><tr><td><code>$page_view</code></td><td><p>Event collected when a page loads.</p><ul><li>Web: page title</li><li>App: Activity, ViewController</li></ul></td><td>O</td><td>O</td><td>O</td><td>Available</td></tr><tr><td><code>$engagement</code></td><td><p>Collects the page a user stayed on and the time spent as properties.<br>Can be used for the following data analysis:</p><ul><li>Average dwell time per page</li><li>Average dwell time per user</li></ul></td><td>O</td><td>O</td><td>O</td><td>Available</td></tr><tr><td><code>$session_start</code></td><td>Automatically collected when a session starts.</td><td>O</td><td>O</td><td>O</td><td>Available</td></tr><tr><td><code>$session_end</code></td><td>Collected when a session ends.</td><td>O</td><td>O</td><td>O</td><td>Available</td></tr><tr><td><code>$app_install</code></td><td>Collected on the first launch after app installation.</td><td>X</td><td>O</td><td>O</td><td>Available</td></tr><tr><td><code>$app_update</code></td><td>Collected on the first launch after an app update.</td><td>X</td><td>O</td><td>O</td><td>Available</td></tr><tr><td><code>$app_open</code></td><td>Collected when the app is launched or reactivated.</td><td>X</td><td>O</td><td>O</td><td>Available</td></tr><tr><td><code>$app_background</code></td><td>Collected when the app transitions from an active state (foreground) to an inactive state (background).</td><td>X</td><td>O</td><td>O</td><td>Available</td></tr></tbody></table>

## 2. User Property Collection Events

Events collected when a function is called via SDK/API to update user properties.

<table data-full-width="true"><thead><tr><th width="194.95703125">Event Key</th><th width="350.60546875">Description</th><th width="78.82421875">Web</th><th width="77.53515625">App</th><th width="73.84765625">Billing</th><th width="92.7265625">on/off</th></tr></thead><tbody><tr><td><code>$properties</code></td><td>An event automatically created by the SDK when general user properties are updated.</td><td>O</td><td>O</td><td>X</td><td>Not available</td></tr><tr><td><code>$push_subscriptions</code></td><td>An event automatically created by the SDK when the push channel subscription consent among CRM user properties is updated.</td><td>O</td><td>O</td><td>O</td><td>Not available</td></tr><tr><td><code>$kakao_subscriptions</code></td><td>An event automatically created by the SDK when the Kakao Message channel subscription consent among CRM user properties is updated.</td><td>O</td><td>O</td><td>O</td><td>Not available</td></tr><tr><td><code>$sms_subscriptions</code></td><td>An event automatically created by the SDK when the Text Message channel subscription consent among CRM user properties is updated.</td><td>O</td><td>O</td><td>O</td><td>Not available</td></tr></tbody></table>

## 3. CRM Campaign Events

Events occurring from In-App Messages, Push Messages, Kakao Messages, Text Messages, Webhooks, and User Journeys in CRM campaigns are auto-collected and always collected for performance measurement.

<table data-full-width="true"><thead><tr><th width="200.41015625">Event Key</th><th width="370.30859375">Description</th><th width="82.42578125">Web</th><th width="76.4921875">App</th><th width="73.82421875">Billing</th><th width="89.69140625">on/off</th></tr></thead><tbody><tr><td><code>$in_app_impression</code></td><td>Event that occurs when an In-App Message is displayed.</td><td>O</td><td>O</td><td>O</td><td>Not available</td></tr><tr><td><code>$in_app_action</code></td><td>Event that occurs when an In-App Message is clicked.</td><td>O</td><td>O</td><td>O</td><td>Not available</td></tr><tr><td><code>$push_send</code></td><td>Event that occurs when a Push Message is sent.</td><td>X</td><td>O</td><td>O</td><td>Not available</td></tr><tr><td><code>$push_click</code></td><td>Event that occurs when a Push Message is clicked.</td><td>X</td><td>O</td><td>O</td><td>Not available</td></tr><tr><td><code>$kakao_send</code></td><td>Event that occurs when a Kakao Message is sent.</td><td>-</td><td>-</td><td>O</td><td>Not available</td></tr><tr><td><code>$sms_send</code></td><td>Event that occurs when a Text Message is sent.</td><td>-</td><td>-</td><td>O</td><td>Not available</td></tr><tr><td><code>$webhook_send</code></td><td>Event that occurs when a Webhook is sent.</td><td>-</td><td>-</td><td>O</td><td>Not available</td></tr><tr><td><code>$journey_entry</code></td><td>Event that occurs when a user enters a journey.</td><td>O</td><td>O</td><td>O</td><td>Not available</td></tr><tr><td><code>$journey_node</code></td><td>Event that occurs when a user enters a specific node (step) of a journey.</td><td>O</td><td>O</td><td>O</td><td>Not available</td></tr><tr><td><code>$journey_complete</code></td><td>Event that occurs when a user completes a journey.</td><td>O</td><td>O</td><td>O</td><td>Not available</td></tr></tbody></table>


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