系统事件
以 $ 开头的名称属于平台：SDK 会自行发送它们，控制台会把它们显示在你的事件旁边。这是说明每一个含义及其携带内容的唯一清单。
| Event | Sent by | What it means | What it carries |
|---|---|---|---|
| <code>$autocapture</code> | Web SDK | A click anywhere on the page, with the element that was clicked. The web SDK sends it by default; autocapture: false or autocaptureOptions.clicks: false turns it off. | <code>$event_type</code>, <code>$el_tag</code>, <code>$el_text</code>, <code>$el_id</code>, <code>$el_classes</code>, <code>$el_href</code>, <code>$current_url</code>, <code>$pathname</code>, <code>$host</code>, <code>$title</code>, <code>$referrer</code> |
| <code>$pageview</code> | Web SDK | A page shown, including every client-side navigation the History API makes: one per distinct path and query. | <code>$current_url</code>, <code>$pathname</code>, <code>$host</code>, <code>$title</code>, <code>$referrer</code> |
| <code>$screen</code> | Flutter | A named route pushed or replaced in a Flutter app, the mobile counterpart of $pageview. | <code>screen</code> |
| <code>$identify</code> | Every SDK | A person becomes known by a distinct id. The anonymous trail before it is joined to them, and any traits ride along under $set. | <code>$anon_distinct_id</code>, <code>$set</code> |
| <code>$create_alias</code> | Every SDK | A second id for the same person, so events sent under either resolve to one profile. | <code>alias</code> |
| <code>$group</code> | Every SDK | The person is placed in a group such as a company or a team; group properties ride along under $set. | <code>$group_type</code>, <code>$group_key</code>, <code>$set</code> |
| <code>$set</code> | Every SDK | Person properties written without an identify: $set overwrites, $set_once fills only what is still empty. | <code>$set</code>, <code>$set_once</code> |
| <code>$feature_flag_called</code> | Every SDK | A flag was evaluated for this person, sent once per distinct answer. Experiments attribute exposure from it. | <code>$feature_flag</code>, <code>$feature_flag_response</code> |
A leading $ is reserved: the ingest API accepts any such name from an SDK and rejects one from your own code, so a product event is always a lowercase dotted name like order.completed. The same rule marks the reserved property keys above, and $set, $set_once and $unset are the three that write user state; how they fold into a profile is on the Data model page, and the wire bounds are on Ingest API.
In the console, every one of these appears beside your own events on Events, in the catalog behind every event picker, and in the top movers on Home. $autocapture is the busiest of them on a web property: one row per click, so a product with autocapture on sees it lead the volume band.