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# App

## App

**Status:** ![Development](https://img.shields.io/badge/-development-blue)

**type:** `app`

**Description:** An app used directly by end users — like mobile, web, or desktop.

**Other Attributes:**

> :warning: This entity definition contains attributes without a role.
> Stable Entities MUST NOT have attributes without a defined role.

| Attribute  | Type | Description  | Examples  | [Requirement Level](https://opentelemetry.io/docs/specs/semconv/general/attribute-requirement-level/) | Stability |
|---|---|---|---|---|---|
| [`app.installation.id`](/docs/registry/attributes/app.md) | string | A unique identifier representing the installation of an application on a specific device [1] | `2ab2916d-a51f-4ac8-80ee-45ac31a28092` | `Recommended` | ![Development](https://img.shields.io/badge/-development-blue) |

**[1] `app.installation.id`:** Its value SHOULD persist across launches of the same application installation, including through application upgrades.
It SHOULD change if the application is uninstalled or if all applications of the vendor are uninstalled.
Additionally, users might be able to reset this value (e.g. by clearing application data).
If an app is installed multiple times on the same device (e.g. in different accounts on Android), each `app.installation.id` SHOULD have a different value.
If multiple OpenTelemetry SDKs are used within the same application, they SHOULD use the same value for `app.installation.id`.
Hardware IDs (e.g. serial number, IMEI, MAC address) MUST NOT be used as the `app.installation.id`.

For iOS, this value SHOULD be equal to the [vendor identifier](https://developer.apple.com/documentation/uikit/uidevice/identifierforvendor).

For Android, examples of `app.installation.id` implementations include:

- [Firebase Installation ID](https://firebase.google.com/docs/projects/manage-installations).
- A globally unique UUID which is persisted across sessions in your application.
- [App set ID](https://developer.android.com/identity/app-set-id).
- [`Settings.getString(Settings.Secure.ANDROID_ID)`](https://developer.android.com/reference/android/provider/Settings.Secure#ANDROID_ID).

More information about Android identifier best practices can be found [here](https://developer.android.com/training/articles/user-data-ids).


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