What is the identifier for advertisers (IDFA)?

The Identifier for Advertisers (IDFA) is a random device identifier assigned by Apple to a user’s device. Advertisers use this to track data so they can deliver customized advertising. The IDFA is used for tracking and identifying a user (without revealing personal information).

The data can then be used to discover information such as which in-app events a user triggers. The IDFA can also identify when users interact with a mobile advertising campaign, provided the channel offers IDFA tracking and the advertiser tracks users who interact with as successfully. If this occurs, the IDFA can identify whether specific users click an advert for payment and attribution purposes.

IDFAs are important because they are an accurate means to track iOS users. By assigning a device to a single IDFA, advertisers who are able to track IDFAs within a campaign have greater certainty about the defining qualities of that user and whether they installed due to an advertising campaign. IDFAs also offer a welcome level of privacy for users. This can have additional effects for advertisers, while the IDFA’s depersonalization of user data ensures that it is on the right side of data protection efforts.

The Android equivalent to the Identifier for Advertisers is called a GPS ADID (or Google Play Services ID for Android). A user has access to their GPS ADID in their settings menu under ‘Google - Ads.’ They can also reset the ID and opt-out of ad personalization. To learn more about these terms, take a look at our introduction to app tracking.

IDFAs are one of the most precise ways to track a mobile advertising campaign on iOS, but users are increasingly opting out of using it.

Apple introduced a way for users to show that they didn’t want to be tracked. By activating an option called ‘limit ad tracking’ (or LAT), user information would be shown as blank, and as such those users can’t be shown targeted ads. As it stands, roughly 20% of iOS users cannot be tracked using the IDFA because they have enabled LAT.

Adjust can track users who do consent to companies accessing their IDFA and the associated data. IDFAs can be tracked using Adjust’s tracker URLs to help advertisers segment their users. Adjust also offers attribution services for Apple’s Search Ads, which exist exclusively on iOS and will only include users who have the IDFA activated.

Furthermore, marketers can use Adjust’s Privacy Insights to understand how many users have activated LAT. By using one-way cryptographic hashing to identify LAT usage without identifying anything about the user, we can help marketers to spot users who limit tracking so they can see its impact on the audience for their iOS app in full.