> ## Documentation Index
> Fetch the complete documentation index at: https://help.airbridge.io/llms.txt
> Use this file to discover all available pages before exploring further.

# Identifiers

Airbridge gathers as many identifiers as possible and chooses the most suitable one for various purposes.

<h2 id="types-of-identifiers-used-in-airbridge">
  Types of Identifiers Used in Airbridge
</h2>

Airbridge uses 4 main types of identifiers: Airbridge Device ID, User ID, Cookie ID, and Airbridge ID.

* Airbridge Device ID is used to identify users in app environments.
* User ID and Cookie ID are used to identify users in web environments. These are also used in features that transmit or export identifiers, such as Audience Manager and Raw Data Export.
* Airbridge ID is used to consolidate app and web user journeys. The Funnel, Retention, and Revenue reports use the Airbridge ID to count users when the **\[Identifier]** is set to **User**.

<h3 id="airbridge-device-id">
  Airbridge Device ID
</h3>

Airbridge Device ID is used to identify users based on their device.

* For Android, Airbridge collects GAID and App Set ID, and for iOS, it collects IDFA and IDFV. Among these, the most suitable identifier is selected and used as the Airbridge Device ID.

If none of these identifiers are available, the Airbridge SDK generates a Random Generated ID.

Below is a list of identifiers that Airbridge may use as candidates for the Airbridge Device ID.

<Accordion title="Identifier candidates for Airbridge Device ID">
  | Identifier          | Source    | Description                                                                                                                                                                            |
  | ------------------- | --------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
  | GAID                | Android   | A unique identifier provided per device in Android.                                                                                                                                    |
  | AppSetID            | Android   | An identifier provided per developer account in Android. The same identifier is used across different apps if they belong to the same developer.                                       |
  | IDFA                | iOS       | A unique identifier provided per device in iOS. Starting from iOS 14.5, it is only available if the user consents to the data tracking via the ATT (App Tracking Transparency) prompt. |
  | IDFV                | iOS       | An identifier provided per developer account in iOS. The same identifier is used across different apps if they belong to the same developer.                                           |
  | Random Generated ID | Airbridge | When no identifiers are available on Android or iOS, the Airbridge SDK generates a random ID.                                                                                          |

  These identifiers typically appear as 32-character alphanumeric strings, such as `38400000-8cf0-11bd-b23e-10b96e40000d`.
</Accordion>

Below are the Airbridge features where the Airbridge Device ID is used.

<div id="note" />

<Info>
  **Note**

  Since only one of the candidate identifiers is selected as the Airbridge Device ID, the identifier used may vary depending on the specific Airbridge feature.
</Info>

<div style={{ overflowX: 'auto' }}>
  <table style={{ display: 'table' }}>
    <thead>
      <tr>
        <th width="80px">
          Airbridge Feature
        </th>

        <th width="240px">
          Scope of Usage
        </th>
      </tr>
    </thead>

    <tbody>
      <tr>
        <td>
          Overview Dashboard, Actuals Report, Trend Report
        </td>

        <td>
          · Metrics ending in “Users (App)”<br />· Cohort metrics<br />· GroupBy settings using "Is First Event Per Device ID"
        </td>
      </tr>

      <tr>
        <td>
          Retention Report
        </td>

        <td>
          All data aggregated when the **\[Identifier]** is set to **Device**
        </td>
      </tr>

      <tr>
        <td>
          Revenue Report
        </td>

        <td>
          **User Count**, **ARPU**, **ARPPU**, and **PUR** metrics and the **Users**, **Paying Users**, and **CAC** sub-metrics, when the **\[Identifier]** is set to **Device**
        </td>
      </tr>

      <tr>
        <td>
          Active User Report
        </td>

        <td>
          “DAU (App)”, “Paying Users (App)”, “ARPU (App)”, “ARPPU (App)”
        </td>
      </tr>

      <tr>
        <td>
          Funnel Report
        </td>

        <td>
          "Device" as identifier
        </td>
      </tr>

      <tr>
        <td>
          Audience Manager
        </td>

        <td>
          “Audience Identifier” sent to ad channels
        </td>
      </tr>

      <tr>
        <td>
          App Raw Data Export
        </td>

        <td>
          “Airbridge Device ID”, “Airbridge Device ID Type”, and “Is First Event Per Device ID” that can be selected from the \[Select Event Property] step
        </td>
      </tr>
    </tbody>
  </table>
</div>

<h3 id="user-id">
  User ID
</h3>

User ID is used to identify users based on the information they provide when signing up or logging in to your service. If Airbridge can't collect this information directly, the client must send the user ID via a server-to-server (S2S) integration.

Below are the Airbridge features where the user ID is used.

| Airbridge Features                               | Scope of Use                                                                                                                                                                                                            |
| ------------------------------------------------ | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| Overview Dashboard, Actuals Report, Trend Report | GroupBy settings using "Is First Event Per User ID"                                                                                                                                                                     |
| Active User Report                               | "DAU (Web)", "Paying Users (Web)", "ARPU (Web)", "ARPPU (Web)"                                                                                                                                                          |
| Web Raw Data Export                              | "User ID", "Is First Event per User ID", "Is First Event per User ID By Airbridge", "Is First Event per User ID By", "Is First Event per User ID By Client" that can be selected from the \[Select Event Property] step |

<h3 id="cookie-id">
  Cookie ID
</h3>

Cookie ID is used to identify users based on information stored in cookies in web environments. Below are the Airbridge features where the cookie ID is used.

| Airbridge Features                               | Scope of Use                                                                                                                                                                                                                         |
| ------------------------------------------------ | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
| Overview Dashboard, Actuals Report, Trend Report | Metrics ending in “Users (Web)”                                                                                                                                                                                                      |
| Active User Report                               | "DAU (Web)", "Paying Users (Web)", "ARPU (Web)", "ARPPU (Web)"                                                                                                                                                                       |
| Web Raw Data Export                              | "Cookie ID", "User ID", "Is First Event per User ID", "Is First Event per User ID By Airbridge", "Is First Event per User ID By", "Is First Event per User ID By Client" that can be selected from the \[Select Event Property] step |

<h3 id="airbridge-id">
  Airbridge ID
</h3>

Airbridge ID is used to identify users by utilizing both the user ID and the Airbridge device ID when available. It is primarily generated based on the user ID, and if the user ID is not available, it is generated based on the Airbridge device ID. Airbridge ID is created by Airbridge to track user journeys across both app and web environments.

Below are the Airbridge features where Airbridge ID is used.

| Airbridge Features                              | Scope of Use         |
| ----------------------------------------------- | -------------------- |
| Funnel Report, Retention Report, Revenue Report | "User" as identifier |

<h4 id="determining-first-events">
  Determining first events
</h4>

Airbridge determines whether an event is the first based on either the Airbridge device ID or the user ID.

<AccordionGroup>
  <Accordion title="Is First Event per Device ID">
    When this GroupBy option is selected, Airbridge determines whether an app event is the first based on the Airbridge Device ID. If the event is the first based on the Airbridge Device ID, it is marked as `true`. If not, it is marked as `false`. If the Airbridge Device ID is missing or invalid, the value is shown as `null`.

    Refer to the example below.

    | Airbridge Device ID | Event Category | Is First Event per Device ID | Event Datetime      |
    | ------------------- | -------------- | ---------------------------- | ------------------- |
    | D1                  | Install (App)  | true                         | 2020-06-22 21:36:00 |
    | D1                  | Install (App)  | false                        | 2020-06-23 09:00:00 |
  </Accordion>

  <Accordion title="Is First Event per User ID">
    When this GroupBy option is selected, Airbridge determines whether a web or app event is the first based on the user ID. If the event is the first based on the user ID, it is marked as `true`. If not, it is marked as `false`. If the user ID is missing or invalid, the value is shown as `null`.

    Refer to the example below.

    | User ID | Event Category       | Is First Event per User ID | Event Datetime      |
    | ------- | -------------------- | -------------------------- | ------------------- |
    | U1      | Order Complete (App) | true                       | 2020-06-24 17:00:00 |
    | U1      | Order Complete (Web) | false                      | 2020-06-25 18:00:00 |

    In this example, the Order Complete event that occurred in the app is the first event. Although the Order Complete event on the web is the first from the web’s perspective, it is not considered the first event because first-event determination takes both web and app events into account.
  </Accordion>
</AccordionGroup>

<h2 id="understanding-identifiers-used-in-airbridge">
  Understanding Identifiers Used in Airbridge
</h2>

<div id="note-2" />

<Info>
  **Note**

  The identifiers in the scenarios below are simplified to facilitate your understanding; real-world identifiers are more complex.
</Info>

Identifiers used in Airbridge are not always collected. For example, Airbridge Device ID may be unavailable due to LAT (Limited Ad Tracking) or ATT (App Tracking Transparency) policies. Similarly, the user ID may not be available if the user does not sign up or log into your service.

<h4 id="determining-unique-users-in-reports">
  Determining unique users in reports
</h4>

Unique users refer to distinct users in reports, excluding those counted multiple times based on identifiers.

<AccordionGroup>
  <Accordion title="When multiple device IDs are connected to a single user ID">
    In general, when a user uses multiple devices to use your service, multiple device IDs will be collected, as illustrated in the table below.

    ###### Table

    <div style={{ overflowX: 'auto' }}>
      <table style={{ display: 'table' }}>
        <thead>
          <tr>
            <th width="120px">
              Device ID
            </th>

            <th width="120px">
              User ID
            </th>

            <th width="120px">
              Airbridge ID
            </th>
          </tr>
        </thead>

        <tbody>
          <tr>
            <td>
              T
            </td>

            <td>
              Rachel
            </td>

            <td>
              200
            </td>
          </tr>

          <tr>
            <td>
              A
            </td>

            <td>
              Rachel
            </td>

            <td>
              200
            </td>
          </tr>

          <tr>
            <td>
              C
            </td>

            <td>
              Rachel
            </td>

            <td>
              200
            </td>
          </tr>
        </tbody>
      </table>
    </div>

    ###### Determining unique users

    To generate the Airbridge ID, Airbridge ties each user ID (Rachel) to the respective device IDs (T, A, C).

    As a result, when using the user ID or the Airbridge ID, only 1 unique user is identified. When using the device ID, 3 unique users are identified because each device ID is considered to be a different user.
  </Accordion>

  <Accordion title="When multiple user IDs are connected to a single device ID">
    Multiple users may be sharing a single device, as illustrated in the table below.

    ###### Table

    <div style={{ overflowX: 'auto' }}>
      <table style={{ display: 'table' }}>
        <thead>
          <tr>
            <th width="120px">
              Device ID
            </th>

            <th width="120px">
              User ID
            </th>

            <th width="120px">
              Airbridge ID
            </th>
          </tr>
        </thead>

        <tbody>
          <tr>
            <td>
              B
            </td>

            <td>
              Daniel
            </td>

            <td>
              56
            </td>
          </tr>

          <tr>
            <td>
              B
            </td>

            <td>
              Amy
            </td>

            <td>
              57
            </td>
          </tr>
        </tbody>
      </table>
    </div>

    ###### Determining unique users

    To generate the Airbridge ID, Airbridge ties each of the 2 user IDs (Daniel, Amy) to the respective device ID (B).

    As a result, when using the user ID or the Airbridge ID, 2 unique users are identified. When using the device ID, only 1 unique user is identified.
  </Accordion>

  <Accordion title="When the user ID is not available">
    Oftentimes, the user ID is not available because the user does not bother to sign in every time. Without the user ID to be matched with device IDs, the Airbridge ID is generated for each device ID, as illustrated in the table below.

    ###### Table

    <div style={{ overflowX: 'auto' }}>
      <table style={{ display: 'table' }}>
        <thead>
          <tr>
            <th width="120px">
              Device ID
            </th>

            <th width="120px">
              User ID
            </th>

            <th width="120px">
              Airbridge ID
            </th>
          </tr>
        </thead>

        <tbody>
          <tr>
            <td>
              X
            </td>

            <td>
              Noel
            </td>

            <td>
              300
            </td>
          </tr>

          <tr>
            <td>
              Y
            </td>

            <td>
              \-
            </td>

            <td>
              301
            </td>
          </tr>

          <tr>
            <td>
              Z
            </td>

            <td>
              \-
            </td>

            <td>
              302
            </td>
          </tr>

          <tr>
            <td>
              Z
            </td>

            <td>
              \-
            </td>

            <td>
              302
            </td>
          </tr>
        </tbody>
      </table>
    </div>

    ###### Determining unique users

    Multiple users may be sharing a single device whose device ID is Z. However, because there are no multiple user IDs available, a separate Airbridge ID (302) is generated for the device ID (Z).

    As a result, when using the device ID or the Airbridge ID, 3 unique users are identified. When using the user ID, only 1 unique user is identified because users whose user ID is not available cannot be identified.
  </Accordion>

  <Accordion title="When multiple user IDs and multiple device IDs are available">
    Real-world scenarios are often complex, as illustrated in the table below.

    ###### Table

    <div style={{ overflowX: 'auto' }}>
      <table style={{ display: 'table' }}>
        <thead>
          <tr>
            <th width="120px">
              Device ID
            </th>

            <th width="120px">
              User ID
            </th>

            <th width="120px">
              Airbridge ID
            </th>
          </tr>
        </thead>

        <tbody>
          <tr>
            <td>
              A
            </td>

            <td>
              Tai
            </td>

            <td>
              400
            </td>
          </tr>

          <tr>
            <td>
              B
            </td>

            <td>
              Sunny
            </td>

            <td>
              401
            </td>
          </tr>

          <tr>
            <td>
              C
            </td>

            <td>
              Dana
            </td>

            <td>
              402
            </td>
          </tr>

          <tr>
            <td>
              D
            </td>

            <td>
              Dana
            </td>

            <td>
              402
            </td>
          </tr>

          <tr>
            <td>
              E
            </td>

            <td>
              Dana
            </td>

            <td>
              402
            </td>
          </tr>

          <tr>
            <td>
              F
            </td>

            <td>
              \-
            </td>

            <td>
              403
            </td>
          </tr>
        </tbody>
      </table>
    </div>

    ###### Determining unique users

    To generate the Airbridge ID, Airbridge ties each of the 3 user IDs (Tai, Sunny, Dana) to the respective device IDs (A, B, C, D, E). Note that there is a case where 1 user ID (Dana) is tied to 3 device IDs (C, D, E). For the user whose device ID is available but the user ID is not, a separate Airbridge ID (403) is generated for the device ID (F).

    As a result, when using the Airbridge ID, 4 unique users are identified. When using the user ID, 3 unique users are identified, and when using the device ID, 6 unique users are identified.
  </Accordion>
</AccordionGroup>

<link rel="alternate" hrefLang="en" href="https://help.airbridge.io/en/guides/identifiers" />

<link rel="alternate" hrefLang="ko" href="https://help.airbridge.io/ko/guides/identifiers" />