What is a device ID?

A device ID is a unique, anonymized string of numbers and letters that identifies every individual smartphone or tablet in the world. It is stored on the mobile device and can be retrieved by any app that is downloaded and installed. Apps typically retrieve the ID for identification when talking to servers.

There’s been a recent shift in the industry toward user privacy, with a move toward aggregated data in place of user-level (device ID-based) data. Most significantly is the rollout of iOS 14.5 in April of 2021, along with the introduction of Apple’s App Tracking Transparency (ATT), which requires developers to request permission to access a user’s device ID.

• On iOS, a device ID is called the ‘Identifier For Advertisers’ (IDFA for short) and is made up of 8 digits and a dash, followed by three sets of 4 digits. Since iOS 14.5, users can opt-in or opt-out of sharing this ID with developers and advertisers on an app-by-app basis after receiving an opt-in prompt.

• On Android, the device ID is the Android Advertising ID (AAID). Users are able to access their AAID within the settings menu under ‘Google - Ads,’ as well as reset the ID, and opt-out of ad personalization. As of Android 12 (released in June 2021), the AAID is zeroed out for all users who have opted out of ad personalization in their settings. These users are otherwise known as ‘Limited Ad Tracking’ users.

Device IDs are the easiest way to identify mobile users, as they allow you to track individual devices. This not only reveals certain user behaviour (which can be aggregated to identify trends) but also allows you to put users into cohorts based on understood identifiers such as geographic region or device. Essentially, if you’re able to track a user’s device ID, you are able to create a much clearer picture of how they behave.

If a publisher allows you to track device IDs from their platform, it’s easy to see whether users have looked at your ad and whether they clicked to install. It can also show how a user interacts with your app after install. This is because you can track the Device ID throughout the process. Testing users for a better understanding of a cohort (such as for creative, or ad optimization) also improves due to the use of unique user IDs.

The Adjust platform generates internal IDs, as well as registering device IDs. We do this because device IDs are only available intermittently, and are not consistently tracked as if there was one single, unchanging number. Because of this, we can create a more consistent user profile.

Our generated IDs also include some extra rules that make them better as a privacy-compliant analytics package, mainly because they’re not personally identifiable in the same way as IDFAs. This means the privacy of your users is safe.

Adjust offers several attribution methods, depending on ad engagement and conversion type. To find out more about Adjust’s attribution methods, take a look at our official documentation.

We also offer full support for marketers and developers post iOS 14.5, helping clients to understand SKAdNetwork’s conversion value mechanism and how to develop strategies that make the most of it.